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/// \file meta.hpp Tiny meta-programming library.
//
// Meta library
//
// Copyright Eric Niebler 2014-present
//
// Use, modification and distribution is subject to the
// Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/ericniebler/meta
//
#ifndef META_HPP
#define META_HPP
#include <cstddef>
#include <initializer_list>
#include <meta/meta_fwd.hpp>
#include <type_traits>
#include <utility>
#ifdef __clang__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunknown-pragmas"
#pragma GCC diagnostic ignored "-Wpragmas"
#pragma GCC diagnostic ignored "-Wdocumentation-deprecated-sync"
#pragma GCC diagnostic ignored "-Wmissing-variable-declarations"
#endif
/// \defgroup meta Meta
///
/// A tiny metaprogramming library
/// \defgroup trait Trait
/// Trait invocation/composition.
/// \ingroup meta
/// \defgroup invocation Invocation
/// Trait invocation
/// \ingroup trait
/// \defgroup composition Composition
/// Trait composition
/// \ingroup trait
/// \defgroup logical Logical
/// Logical operations
/// \ingroup meta
/// \defgroup algorithm Algorithms
/// Algorithms.
/// \ingroup meta
/// \defgroup query Query/Search
/// Query and search algorithms
/// \ingroup algorithm
/// \defgroup transformation Transformation
/// Transformation algorithms
/// \ingroup algorithm
/// \defgroup runtime Runtime
/// Runtime algorithms
/// \ingroup algorithm
/// \defgroup datatype Datatype
/// Datatypes.
/// \ingroup meta
/// \defgroup list list_like
/// \ingroup datatype
/// \defgroup integral Integer sequence
/// Equivalent to C++14's `std::integer_sequence`
/// \ingroup datatype
/// \defgroup extension Extension
/// Extend meta with your own datatypes.
/// \ingroup datatype
/// \defgroup math Math
/// Integral constant arithmetic.
/// \ingroup meta
/// \defgroup lazy_trait lazy
/// \ingroup trait
/// \defgroup lazy_invocation lazy
/// \ingroup invocation
/// \defgroup lazy_composition lazy
/// \ingroup composition
/// \defgroup lazy_logical lazy
/// \ingroup logical
/// \defgroup lazy_query lazy
/// \ingroup query
/// \defgroup lazy_transformation lazy
/// \ingroup transformation
/// \defgroup lazy_list lazy
/// \ingroup list
/// \defgroup lazy_datatype lazy
/// \ingroup datatype
/// \defgroup lazy_math lazy
/// \ingroup math
/// Tiny metaprogramming library
namespace meta
{
namespace detail
{
/// Returns a \p T nullptr
template <typename T>
constexpr T *_nullptr_v()
{
return nullptr;
}
#if META_CXX_VARIABLE_TEMPLATES
template <typename T>
META_INLINE_VAR constexpr T *nullptr_v = nullptr;
#endif
} // namespace detail
/// An empty type.
/// \ingroup datatype
struct nil_
{
};
/// Type alias for \p T::type.
/// \ingroup invocation
template <META_TYPE_CONSTRAINT(trait) T>
using _t = typename T::type;
#if META_CXX_VARIABLE_TEMPLATES || defined(META_DOXYGEN_INVOKED)
/// Variable alias for \c T::type::value
/// \note Requires C++14 or greater.
/// \ingroup invocation
template <META_TYPE_CONSTRAINT(integral) T>
constexpr typename T::type::value_type _v = T::type::value;
#endif
/// Lazy versions of meta actions
namespace lazy
{
/// \sa `meta::_t`
/// \ingroup lazy_invocation
template <typename T>
using _t = defer<_t, T>;
} // namespace lazy
/// An integral constant wrapper for \c std::size_t.
/// \ingroup integral
template <std::size_t N>
using size_t = std::integral_constant<std::size_t, N>;
/// An integral constant wrapper for \c bool.
/// \ingroup integral
template <bool B>
using bool_ = std::integral_constant<bool, B>;
/// An integral constant wrapper for \c int.
/// \ingroup integral
template <int I>
using int_ = std::integral_constant<int, I>;
/// An integral constant wrapper for \c char.
/// \ingroup integral
template <char Ch>
using char_ = std::integral_constant<char, Ch>;
///////////////////////////////////////////////////////////////////////////////////////////
// Math operations
/// An integral constant wrapper around the result of incrementing the wrapped integer \c
/// T::type::value.
template <META_TYPE_CONSTRAINT(integral) T>
using inc = std::integral_constant<decltype(T::type::value + 1), T::type::value + 1>;
/// An integral constant wrapper around the result of decrementing the wrapped integer \c
/// T::type::value.
template <META_TYPE_CONSTRAINT(integral) T>
using dec = std::integral_constant<decltype(T::type::value - 1), T::type::value - 1>;
/// An integral constant wrapper around the result of adding the two wrapped integers
/// \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using plus = std::integral_constant<decltype(T::type::value + U::type::value),
T::type::value + U::type::value>;
/// An integral constant wrapper around the result of subtracting the two wrapped integers
/// \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using minus = std::integral_constant<decltype(T::type::value - U::type::value),
T::type::value - U::type::value>;
/// An integral constant wrapper around the result of multiplying the two wrapped integers
/// \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using multiplies = std::integral_constant<decltype(T::type::value * U::type::value),
T::type::value * U::type::value>;
/// An integral constant wrapper around the result of dividing the two wrapped integers \c
/// T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using divides = std::integral_constant<decltype(T::type::value / U::type::value),
T::type::value / U::type::value>;
/// An integral constant wrapper around the result of negating the wrapped integer
/// \c T::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T>
using negate = std::integral_constant<decltype(-T::type::value), -T::type::value>;
/// An integral constant wrapper around the remainder of dividing the two wrapped integers
/// \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using modulus = std::integral_constant<decltype(T::type::value % U::type::value),
T::type::value % U::type::value>;
/// A Boolean integral constant wrapper around the result of comparing \c T::type::value and
/// \c U::type::value for equality.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using equal_to = bool_<T::type::value == U::type::value>;
/// A Boolean integral constant wrapper around the result of comparing \c T::type::value and
/// \c U::type::value for inequality.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using not_equal_to = bool_<T::type::value != U::type::value>;
/// A Boolean integral constant wrapper around \c true if \c T::type::value is greater than
/// \c U::type::value; \c false, otherwise.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using greater = bool_<(T::type::value > U::type::value)>;
/// A Boolean integral constant wrapper around \c true if \c T::type::value is less than \c
/// U::type::value; \c false, otherwise.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using less = bool_<(T::type::value < U::type::value)>;
/// A Boolean integral constant wrapper around \c true if \c T::type::value is greater than
/// or equal to \c U::type::value; \c false, otherwise.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using greater_equal = bool_<(T::type::value >= U::type::value)>;
/// A Boolean integral constant wrapper around \c true if \c T::type::value is less than or
/// equal to \c U::type::value; \c false, otherwise.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using less_equal = bool_<(T::type::value <= U::type::value)>;
/// An integral constant wrapper around the result of bitwise-and'ing the two wrapped
/// integers \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using bit_and = std::integral_constant<decltype(T::type::value & U::type::value),
T::type::value & U::type::value>;
/// An integral constant wrapper around the result of bitwise-or'ing the two wrapped
/// integers \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using bit_or = std::integral_constant<decltype(T::type::value | U::type::value),
T::type::value | U::type::value>;
/// An integral constant wrapper around the result of bitwise-exclusive-or'ing the two
/// wrapped integers \c T::type::value and \c U::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T, META_TYPE_CONSTRAINT(integral) U>
using bit_xor = std::integral_constant<decltype(T::type::value ^ U::type::value),
T::type::value ^ U::type::value>;
/// An integral constant wrapper around the result of bitwise-complementing the wrapped
/// integer \c T::type::value.
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral) T>
using bit_not = std::integral_constant<decltype(~T::type::value), ~T::type::value>;
namespace lazy
{
/// \sa 'meta::int'
/// \ingroup lazy_math
template <typename T>
using inc = defer<inc, T>;
/// \sa 'meta::dec'
/// \ingroup lazy_math
template <typename T>
using dec = defer<dec, T>;
/// \sa 'meta::plus'
/// \ingroup lazy_math
template <typename T, typename U>
using plus = defer<plus, T, U>;
/// \sa 'meta::minus'
/// \ingroup lazy_math
template <typename T, typename U>
using minus = defer<minus, T, U>;
/// \sa 'meta::multiplies'
/// \ingroup lazy_math
template <typename T, typename U>
using multiplies = defer<multiplies, T, U>;
/// \sa 'meta::divides'
/// \ingroup lazy_math
template <typename T, typename U>
using divides = defer<divides, T, U>;
/// \sa 'meta::negate'
/// \ingroup lazy_math
template <typename T>
using negate = defer<negate, T>;
/// \sa 'meta::modulus'
/// \ingroup lazy_math
template <typename T, typename U>
using modulus = defer<modulus, T, U>;
/// \sa 'meta::equal_to'
/// \ingroup lazy_math
template <typename T, typename U>
using equal_to = defer<equal_to, T, U>;
/// \sa 'meta::not_equal_t'
/// \ingroup lazy_math
template <typename T, typename U>
using not_equal_to = defer<not_equal_to, T, U>;
/// \sa 'meta::greater'
/// \ingroup lazy_math
template <typename T, typename U>
using greater = defer<greater, T, U>;
/// \sa 'meta::less'
/// \ingroup lazy_math
template <typename T, typename U>
using less = defer<less, T, U>;
/// \sa 'meta::greater_equal'
/// \ingroup lazy_math
template <typename T, typename U>
using greater_equal = defer<greater_equal, T, U>;
/// \sa 'meta::less_equal'
/// \ingroup lazy_math
template <typename T, typename U>
using less_equal = defer<less_equal, T, U>;
/// \sa 'meta::bit_and'
/// \ingroup lazy_math
template <typename T, typename U>
using bit_and = defer<bit_and, T, U>;
/// \sa 'meta::bit_or'
/// \ingroup lazy_math
template <typename T, typename U>
using bit_or = defer<bit_or, T, U>;
/// \sa 'meta::bit_xor'
/// \ingroup lazy_math
template <typename T, typename U>
using bit_xor = defer<bit_xor, T, U>;
/// \sa 'meta::bit_not'
/// \ingroup lazy_math
template <typename T>
using bit_not = defer<bit_not, T>;
} // namespace lazy
/// \cond
namespace detail
{
enum class indices_strategy_
{
done,
repeat,
recurse
};
constexpr indices_strategy_ strategy_(std::size_t cur, std::size_t end)
{
return cur >= end ? indices_strategy_::done
: cur * 2 <= end ? indices_strategy_::repeat
: indices_strategy_::recurse;
}
template <typename T>
constexpr std::size_t range_distance_(T begin, T end)
{
return begin <= end ? static_cast<std::size_t>(end - begin)
: throw "The start of the integer_sequence must not be "
"greater than the end";
}
template <std::size_t End, typename State, indices_strategy_ Status_>
struct make_indices_
{
using type = State;
};
template <typename T, T, typename>
struct coerce_indices_
{
};
} // namespace detail
/// \endcond
///////////////////////////////////////////////////////////////////////////////////////////
// integer_sequence
#if !META_CXX_INTEGER_SEQUENCE
/// A container for a sequence of compile-time integer constants.
/// \ingroup integral
template <typename T, T... Is>
struct integer_sequence
{
using value_type = T;
/// \return `sizeof...(Is)`
static constexpr std::size_t size() noexcept { return sizeof...(Is); }
};
#endif
///////////////////////////////////////////////////////////////////////////////////////////
// index_sequence
/// A container for a sequence of compile-time integer constants of type
/// \c std::size_t
/// \ingroup integral
template <std::size_t... Is>
using index_sequence = integer_sequence<std::size_t, Is...>;
#if META_HAS_MAKE_INTEGER_SEQ && !defined(META_DOXYGEN_INVOKED)
// Implement make_integer_sequence and make_index_sequence with the
// __make_integer_seq builtin on compilers that provide it. (Redirect
// through decltype to workaround suspected clang bug.)
/// \cond
namespace detail
{
template <typename T, T N>
__make_integer_seq<integer_sequence, T, N> make_integer_sequence_();
}
/// \endcond
template <typename T, T N>
using make_integer_sequence = decltype(detail::make_integer_sequence_<T, N>());
template <std::size_t N>
using make_index_sequence = make_integer_sequence<std::size_t, N>;
#else
/// Generate \c index_sequence containing integer constants [0,1,2,...,N-1].
/// \par Complexity
/// \f$ O(log(N)) \f$.
/// \ingroup integral
template <std::size_t N>
using make_index_sequence =
_t<detail::make_indices_<N, index_sequence<0>, detail::strategy_(1, N)>>;
/// Generate \c integer_sequence containing integer constants [0,1,2,...,N-1].
/// \par Complexity
/// \f$ O(log(N)) \f$.
/// \ingroup integral
template <typename T, T N>
using make_integer_sequence =
_t<detail::coerce_indices_<T, 0, make_index_sequence<static_cast<std::size_t>(N)>>>;
#endif
///////////////////////////////////////////////////////////////////////////////////////////
// integer_range
/// Makes the integer sequence <tt>[From, To)</tt>.
/// \par Complexity
/// \f$ O(log(To - From)) \f$.
/// \ingroup integral
template <typename T, T From, T To>
using integer_range =
_t<detail::coerce_indices_<T, From,
make_index_sequence<detail::range_distance_(From, To)>>>;
/// \cond
namespace detail
{
template <typename, typename>
struct concat_indices_
{
};
template <std::size_t... Is, std::size_t... Js>
struct concat_indices_<index_sequence<Is...>, index_sequence<Js...>>
{
using type = index_sequence<Is..., (Js + sizeof...(Is))...>;
};
template <>
struct make_indices_<0u, index_sequence<0>, indices_strategy_::done>
{
using type = index_sequence<>;
};
template <std::size_t End, std::size_t... Values>
struct make_indices_<End, index_sequence<Values...>, indices_strategy_::repeat>
: make_indices_<End, index_sequence<Values..., (Values + sizeof...(Values))...>,
detail::strategy_(sizeof...(Values) * 2, End)>
{
};
template <std::size_t End, std::size_t... Values>
struct make_indices_<End, index_sequence<Values...>, indices_strategy_::recurse>
: concat_indices_<index_sequence<Values...>,
make_index_sequence<End - sizeof...(Values)>>
{
};
template <typename T, T Offset, std::size_t... Values>
struct coerce_indices_<T, Offset, index_sequence<Values...>>
{
using type =
integer_sequence<T, static_cast<T>(static_cast<T>(Values) + Offset)...>;
};
} // namespace detail
/// \endcond
/// Evaluate the invocable \p Fn with the arguments \p Args.
/// \ingroup invocation
template <META_TYPE_CONSTRAINT(invocable) Fn, typename... Args>
using invoke = typename Fn::template invoke<Args...>;
/// Lazy versions of meta actions
namespace lazy
{
/// \sa `meta::invoke`
/// \ingroup lazy_invocation
template <typename Fn, typename... Args>
using invoke = defer<invoke, Fn, Args...>;
} // namespace lazy
/// A trait that always returns its argument \p T. It is also an invocable
/// that always returns \p T.
/// \ingroup trait
/// \ingroup invocation
template <typename T>
struct id
{
#if defined(META_WORKAROUND_CWG_1558) && !defined(META_DOXYGEN_INVOKED)
// Redirect through decltype for compilers that have not
// yet implemented CWG 1558:
static id impl(void *);
template <typename... Ts>
using invoke = _t<decltype(id::impl(static_cast<list<Ts...> *>(nullptr)))>;
#else
template <typename...>
using invoke = T;
#endif
using type = T;
};
/// An alias for type \p T. Useful in non-deduced contexts.
/// \ingroup trait
template <typename T>
using id_t = _t<id<T>>;
namespace lazy
{
/// \sa `meta::id`
/// \ingroup lazy_trait
/// \ingroup lazy_invocation
template <typename T>
using id = defer<id, T>;
} // namespace lazy
/// An alias for `void`.
/// \ingroup trait
#if defined(META_WORKAROUND_CWG_1558) && !defined(META_DOXYGEN_INVOKED)
// Redirect through decltype for compilers that have not
// yet implemented CWG 1558:
template <typename... Ts>
using void_ = invoke<id<void>, Ts...>;
#else
template <typename...>
using void_ = void;
#endif
#if META_CXX_VARIABLE_TEMPLATES
#ifdef META_CONCEPT
/// `true` if `T::type` exists and names a type; `false` otherwise.
/// \ingroup trait
template <typename T>
META_INLINE_VAR constexpr bool is_trait_v = trait<T>;
/// `true` if `T::invoke` exists and names a class template; `false` otherwise.
/// \ingroup trait
template <typename T>
META_INLINE_VAR constexpr bool is_callable_v = invocable<T>;
#else // ^^^ Concepts / No concepts vvv
/// \cond
namespace detail
{
template <typename, typename = void>
META_INLINE_VAR constexpr bool is_trait_ = false;
template <typename T>
META_INLINE_VAR constexpr bool is_trait_<T, void_<typename T::type>> = true;
template <typename, typename = void>
META_INLINE_VAR constexpr bool is_callable_ = false;
template <typename T>
META_INLINE_VAR constexpr bool is_callable_<T, void_<quote<T::template invoke>>> = true;
} // namespace detail
/// \endcond
/// `true` if `T::type` exists and names a type; `false` otherwise.
/// \ingroup trait
template <typename T>
META_INLINE_VAR constexpr bool is_trait_v = detail::is_trait_<T>;
/// `true` if `T::invoke` exists and names a class template; `false` otherwise.
/// \ingroup trait
template <typename T>
META_INLINE_VAR constexpr bool is_callable_v = detail::is_callable_<T>;
#endif // Concepts vs. variable templates
/// An alias for `std::true_type` if `T::type` exists and names a type; otherwise, it's an
/// alias for `std::false_type`.
/// \ingroup trait
template <typename T>
using is_trait = bool_<is_trait_v<T>>;
/// An alias for `std::true_type` if `T::invoke` exists and names a class template;
/// otherwise, it's an alias for `std::false_type`.
/// \ingroup trait
template <typename T>
using is_callable = bool_<is_callable_v<T>>;
#else // ^^^ META_CXX_VARIABLE_TEMPLATES / !META_CXX_VARIABLE_TEMPLATES vvv
/// \cond
namespace detail
{
template <typename, typename = void>
struct is_trait_
{
using type = std::false_type;
};
template <typename T>
struct is_trait_<T, void_<typename T::type>>
{
using type = std::true_type;
};
template <typename, typename = void>
struct is_callable_
{
using type = std::false_type;
};
template <typename T>
struct is_callable_<T, void_<quote<T::template invoke>>>
{
using type = std::true_type;
};
} // namespace detail
/// \endcond
template <typename T>
using is_trait = _t<detail::is_trait_<T>>;
/// An alias for `std::true_type` if `T::invoke` exists and names a class
/// template or alias template; otherwise, it's an alias for
/// `std::false_type`.
/// \ingroup trait
template <typename T>
using is_callable = _t<detail::is_callable_<T>>;
#endif
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <template <typename...> class, typename...>
struct defer_
{
};
template <template <typename...> class C, typename... Ts>
requires valid<C, Ts...> struct defer_<C, Ts...>
{
using type = C<Ts...>;
};
template <typename T, template <T...> class, T...>
struct defer_i_
{
};
template <typename T, template <T...> class C, T... Is>
requires valid_i<T, C, Is...> struct defer_i_<T, C, Is...>
{
using type = C<Is...>;
};
#elif defined(META_WORKAROUND_MSVC_703656) // ^^^ Concepts / MSVC workaround vvv
template <typename, template <typename...> class, typename...>
struct _defer_
{
};
template <template <typename...> class C, typename... Ts>
struct _defer_<void_<C<Ts...>>, C, Ts...>
{
using type = C<Ts...>;
};
template <template <typename...> class C, typename... Ts>
using defer_ = _defer_<void, C, Ts...>;
template <typename, typename T, template <T...> class, T...>
struct _defer_i_
{
};
template <typename T, template <T...> class C, T... Is>
struct _defer_i_<void_<C<Is...>>, T, C, Is...>
{
using type = C<Is...>;
};
template <typename T, template <T...> class C, T... Is>
using defer_i_ = _defer_i_<void, T, C, Is...>;
#else // ^^^ workaround ^^^ / vvv no workaround vvv
template <template <typename...> class C, typename... Ts,
template <typename...> class D = C>
id<D<Ts...>> try_defer_(int);
template <template <typename...> class C, typename... Ts>
nil_ try_defer_(long);
template <template <typename...> class C, typename... Ts>
using defer_ = decltype(detail::try_defer_<C, Ts...>(0));
template <typename T, template <T...> class C, T... Is, template <T...> class D = C>
id<D<Is...>> try_defer_i_(int);
template <typename T, template <T...> class C, T... Is>
nil_ try_defer_i_(long);
template <typename T, template <T...> class C, T... Is>
using defer_i_ = decltype(detail::try_defer_i_<T, C, Is...>(0));
#endif // Concepts vs. MSVC vs. Other
template <typename T>
using _t_t = _t<_t<T>>;
} // namespace detail
/// \endcond
///////////////////////////////////////////////////////////////////////////////////////////
// defer
/// A wrapper that defers the instantiation of a template \p C with type parameters \p Ts in
/// a \c lambda or \c let expression.
///
/// In the code below, the lambda would ideally be written as
/// `lambda<_a,_b,push_back<_a,_b>>`, however this fails since `push_back` expects its first
/// argument to be a list, not a placeholder. Instead, we express it using \c defer as
/// follows:
///
/// \code
/// template <typename L>
/// using reverse = reverse_fold<L, list<>, lambda<_a, _b, defer<push_back, _a, _b>>>;
/// \endcode
///
/// \ingroup invocation
template <template <typename...> class C, typename... Ts>
struct defer : detail::defer_<C, Ts...>
{
};
///////////////////////////////////////////////////////////////////////////////////////////
// defer_i
/// A wrapper that defers the instantiation of a template \p C with integral constant
/// parameters \p Is in a \c lambda or \c let expression.
/// \sa `defer`
/// \ingroup invocation
template <typename T, template <T...> class C, T... Is>
struct defer_i : detail::defer_i_<T, C, Is...>
{
};
///////////////////////////////////////////////////////////////////////////////////////////
// defer_trait
/// A wrapper that defers the instantiation of a trait \p C with type parameters \p Ts in a
/// \c lambda or \c let expression.
/// \sa `defer`
/// \ingroup invocation
template <template <typename...> class C, typename... Ts>
using defer_trait = defer<detail::_t_t, detail::defer_<C, Ts...>>;
///////////////////////////////////////////////////////////////////////////////////////////
// defer_trait_i
/// A wrapper that defers the instantiation of a trait \p C with integral constant
/// parameters \p Is in a \c lambda or \c let expression.
/// \sa `defer_i`
/// \ingroup invocation
template <typename T, template <T...> class C, T... Is>
using defer_trait_i = defer<detail::_t_t, detail::defer_i_<T, C, Is...>>;
/// An alias that computes the size of the type \p T.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup trait
template <typename T>
using sizeof_ = meta::size_t<sizeof(T)>;
/// An alias that computes the alignment required for any instance of the type \p T.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup trait
template <typename T>
using alignof_ = meta::size_t<alignof(T)>;
namespace lazy
{
/// \sa `meta::sizeof_`
/// \ingroup lazy_trait
template <typename T>
using sizeof_ = defer<sizeof_, T>;
/// \sa `meta::alignof_`
/// \ingroup lazy_trait
template <typename T>
using alignof_ = defer<alignof_, T>;
} // namespace lazy
#if META_CXX_VARIABLE_TEMPLATES
/// is
/// Test whether a type \p T is an instantiation of class
/// template \p C.
/// \ingroup trait
template <typename T, template <typename...> class C>
using is = bool_<is_v<T, C>>;
#else
/// is
/// \cond
namespace detail
{
template <typename, template <typename...> class>
struct is_ : std::false_type
{
};
template <typename... Ts, template <typename...> class C>
struct is_<C<Ts...>, C> : std::true_type
{
};
} // namespace detail
/// \endcond
/// Test whether a type \c T is an instantiation of class
/// template \c C.
/// \ingroup trait
template <typename T, template <typename...> class C>
using is = _t<detail::is_<T, C>>;
#endif
/// Compose the Invocables \p Fns in the parameter pack \p Ts.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable)... Fns>
struct compose_
{
};
template <META_TYPE_CONSTRAINT(invocable) Fn0>
struct compose_<Fn0>
{
template <typename... Ts>
using invoke = invoke<Fn0, Ts...>;
};
template <META_TYPE_CONSTRAINT(invocable) Fn0, META_TYPE_CONSTRAINT(invocable)... Fns>
struct compose_<Fn0, Fns...>
{
template <typename... Ts>
using invoke = invoke<Fn0, invoke<compose_<Fns...>, Ts...>>;
};
template <typename... Fns>
using compose = compose_<Fns...>;
namespace lazy
{
/// \sa 'meta::compose'
/// \ingroup lazy_composition
template <typename... Fns>
using compose = defer<compose, Fns...>;
} // namespace lazy
/// Turn a template \p C into an invocable.
/// \ingroup composition
template <template <typename...> class C>
struct quote
{
// Indirection through defer here needed to avoid Core issue 1430
// https://wg21.link/cwg1430
template <typename... Ts>
using invoke = _t<defer<C, Ts...>>;
};
/// Turn a template \p C taking literals of type \p T into a
/// invocable.
/// \ingroup composition
template <typename T, template <T...> class C>
struct quote_i
{
// Indirection through defer_i here needed to avoid Core issue 1430
// https://wg21.link/cwg1430
template <META_TYPE_CONSTRAINT(integral)... Ts>
using invoke = _t<defer_i<T, C, Ts::type::value...>>;
};
#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 8 && \
!defined(META_DOXYGEN_INVOKED)
template <template <typename...> class C>
struct quote_trait
{
template <typename... Ts>
using invoke = _t<invoke<quote<C>, Ts...>>;
};
template <typename T, template <T...> class C>
struct quote_trait_i
{
template <typename... Ts>
using invoke = _t<invoke<quote_i<T, C>, Ts...>>;
};
#else
// clang-format off
/// Turn a trait template \p C into an invocable.
/// \code
/// static_assert(std::is_same_v<invoke<quote_trait<std::add_const>, int>, int const>, "");
/// \endcode
/// \ingroup composition
template <template <typename...> class C>
using quote_trait = compose<quote<_t>, quote<C>>;
/// Turn a trait template \p C taking literals of type \p T into an invocable.
/// \ingroup composition
template <typename T, template <T...> class C>
using quote_trait_i = compose<quote<_t>, quote_i<T, C>>;
// clang-format on
#endif
/// An invocable that partially applies the invocable
/// \p Fn by binding the arguments \p Ts to the \e front of \p Fn.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable) Fn, typename... Ts>
struct bind_front
{
template <typename... Us>
using invoke = invoke<Fn, Ts..., Us...>;
};
/// An invocable that partially applies the invocable \p Fn by binding the
/// arguments \p Us to the \e back of \p Fn.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable) Fn, typename... Us>
struct bind_back
{
template <typename... Ts>
using invoke = invoke<Fn, Ts..., Us...>;
};
namespace lazy
{
/// \sa 'meta::bind_front'
/// \ingroup lazy_composition
template <typename Fn, typename... Ts>
using bind_front = defer<bind_front, Fn, Ts...>;
/// \sa 'meta::bind_back'
/// \ingroup lazy_composition
template <typename Fn, typename... Ts>
using bind_back = defer<bind_back, Fn, Ts...>;
} // namespace lazy
/// Extend meta with your own datatypes.
namespace extension
{
/// A trait that unpacks the types in the type list \p L into the invocable
/// \p Fn.
/// \ingroup extension
template <META_TYPE_CONSTRAINT(invocable) Fn, typename L>
struct apply
{
};
template <META_TYPE_CONSTRAINT(invocable) Fn, typename Ret, typename... Args>
struct apply<Fn, Ret(Args...)> : lazy::invoke<Fn, Ret, Args...>
{
};
template <META_TYPE_CONSTRAINT(invocable) Fn, template <typename...> class T,
typename... Ts>
struct apply<Fn, T<Ts...>> : lazy::invoke<Fn, Ts...>
{
};
template <META_TYPE_CONSTRAINT(invocable) Fn, typename T, T... Is>
struct apply<Fn, integer_sequence<T, Is...>>
: lazy::invoke<Fn, std::integral_constant<T, Is>...>
{
};
} // namespace extension
/// Applies the invocable \p Fn using the types in the type list \p L as
/// arguments.
/// \ingroup invocation
template <META_TYPE_CONSTRAINT(invocable) Fn, typename L>
using apply = _t<extension::apply<Fn, L>>;
namespace lazy
{
template <typename Fn, typename L>
using apply = defer<apply, Fn, L>;
}
/// An invocable that takes a bunch of arguments, bundles them into a type
/// list, and then calls the invocable \p Fn with the type list \p Q.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable) Fn,
META_TYPE_CONSTRAINT(invocable) Q = quote<list>>
using curry = compose<Fn, Q>;
/// An invocable that takes a type list, unpacks the types, and then
/// calls the invocable \p Fn with the types.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable) Fn>
using uncurry = bind_front<quote<apply>, Fn>;
namespace lazy
{
/// \sa 'meta::curry'
/// \ingroup lazy_composition
template <typename Fn, typename Q = quote<list>>
using curry = defer<curry, Fn, Q>;
/// \sa 'meta::uncurry'
/// \ingroup lazy_composition
template <typename Fn>
using uncurry = defer<uncurry, Fn>;
} // namespace lazy
/// An invocable that reverses the order of the first two arguments.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable) Fn>
struct flip
{
private:
template <typename... Ts>
struct impl
{
};
template <typename A, typename B, typename... Ts>
struct impl<A, B, Ts...> : lazy::invoke<Fn, B, A, Ts...>
{
};
public:
template <typename... Ts>
using invoke = _t<impl<Ts...>>;
};
namespace lazy
{
/// \sa 'meta::flip'
/// \ingroup lazy_composition
template <typename Fn>
using flip = defer<flip, Fn>;
} // namespace lazy
/// \cond
namespace detail
{
template <typename...>
struct on_
{
};
template <typename Fn, typename... Gs>
struct on_<Fn, Gs...>
{
template <typename... Ts>
using invoke = invoke<Fn, invoke<compose<Gs...>, Ts>...>;
};
} // namespace detail
/// \endcond
/// Use as `on<Fn, Gs...>`. Creates an invocable that applies invocable \c Fn to the
/// result of applying invocable `compose<Gs...>` to all the arguments.
/// \ingroup composition
template <META_TYPE_CONSTRAINT(invocable)... Fns>
using on_ = detail::on_<Fns...>;
template <typename... Fns>
using on = on_<Fns...>;
namespace lazy
{
/// \sa 'meta::on'
/// \ingroup lazy_composition
template <typename Fn, typename G>
using on = defer<on, Fn, G>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// conditional_t
/// \cond
namespace detail
{
template <bool>
struct _cond
{
template <typename Then, typename Else>
using invoke = Then;
};
template <>
struct _cond<false>
{
template <typename Then, typename Else>
using invoke = Else;
};
} // namespace detail
/// \endcond
/// Select one type or another depending on a compile-time Boolean.
/// \ingroup logical
template <bool If, typename Then, typename Else = void>
using conditional_t = typename detail::_cond<If>::template invoke<Then, Else>;
///////////////////////////////////////////////////////////////////////////////////////////
// if_
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename...>
struct _if_
{
};
template <typename If>
requires integral<If>
struct _if_<If> : std::enable_if<_v<If>>
{
};
template <typename If, typename Then>
requires integral<If>
struct _if_<If, Then> : std::enable_if<_v<If>, Then>
{
};
template <typename If, typename Then, typename Else>
requires integral<If>
struct _if_<If, Then, Else> : std::conditional<_v<If>, Then, Else>
{
};
#elif defined(__clang__)
// Clang is faster with this implementation
template <typename, typename = bool>
struct _if_
{
};
template <typename If>
struct _if_<list<If>, decltype(bool(If::type::value))> : std::enable_if<If::type::value>
{
};
template <typename If, typename Then>
struct _if_<list<If, Then>, decltype(bool(If::type::value))>
: std::enable_if<If::type::value, Then>
{
};
template <typename If, typename Then, typename Else>
struct _if_<list<If, Then, Else>, decltype(bool(If::type::value))>
: std::conditional<If::type::value, Then, Else>
{
};
#else
// GCC seems to prefer this implementation
template <typename, typename = std::true_type>
struct _if_
{
};
template <typename If>
struct _if_<list<If>, bool_<If::type::value>>
{
using type = void;
};
template <typename If, typename Then>
struct _if_<list<If, Then>, bool_<If::type::value>>
{
using type = Then;
};
template <typename If, typename Then, typename Else>
struct _if_<list<If, Then, Else>, bool_<If::type::value>>
{
using type = Then;
};
template <typename If, typename Then, typename Else>
struct _if_<list<If, Then, Else>, bool_<!If::type::value>>
{
using type = Else;
};
#endif
} // namespace detail
/// \endcond
/// Select one type or another depending on a compile-time Boolean.
/// \ingroup logical
#ifdef META_CONCEPT
template <typename... Args>
using if_ = _t<detail::_if_<Args...>>;
/// Select one type or another depending on a compile-time Boolean.
/// \ingroup logical
template <bool If, typename... Args>
using if_c = _t<detail::_if_<bool_<If>, Args...>>;
#else
template <typename... Args>
using if_ = _t<detail::_if_<list<Args...>>>;
template <bool If, typename... Args>
using if_c = _t<detail::_if_<list<bool_<If>, Args...>>>;
#endif
namespace lazy
{
/// \sa 'meta::if_'
/// \ingroup lazy_logical
template <typename... Args>
using if_ = defer<if_, Args...>;
/// \sa 'meta::if_c'
/// \ingroup lazy_logical
template <bool If, typename... Args>
using if_c = if_<bool_<If>, Args...>;
} // namespace lazy
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename...>
struct _and_
{
};
template <>
struct _and_<> : std::true_type
{
};
template <typename B, typename... Bs>
requires integral<B> && (bool(B::type::value))
struct _and_<B, Bs...> : _and_<Bs...>
{
};
template <typename B, typename... Bs>
requires integral<B> && (!bool(B::type::value))
struct _and_<B, Bs...> : std::false_type
{
};
template <typename...>
struct _or_
{
};
template <>
struct _or_<> : std::false_type
{
};
template <typename B, typename... Bs>
requires integral<B> && (bool(B::type::value))
struct _or_<B, Bs...> : std::true_type
{
};
template <typename B, typename... Bs>
requires integral<B> && (!bool(B::type::value))
struct _or_<B, Bs...> : _or_<Bs...>
{
};
#else
template <bool>
struct _and_
{
template <typename...>
using invoke = std::true_type;
};
template <>
struct _and_<false>
{
template <typename B, typename... Bs>
using invoke = invoke<
if_c<!B::type::value, id<std::false_type>, _and_<0 == sizeof...(Bs)>>,
Bs...>;
};
template <bool>
struct _or_
{
template <typename = void>
using invoke = std::false_type;
};
template <>
struct _or_<false>
{
template <typename B, typename... Bs>
using invoke = invoke<
if_c<B::type::value, id<std::true_type>, _or_<0 == sizeof...(Bs)>>,
Bs...>;
};
#endif
} // namespace detail
/// \endcond
/// Logically negate the Boolean parameter
/// \ingroup logical
template <bool B>
using not_c = bool_<!B>;
/// Logically negate the integral constant-wrapped Boolean parameter.
/// \ingroup logical
template <META_TYPE_CONSTRAINT(integral) B>
using not_ = not_c<B::type::value>;
#if META_CXX_FOLD_EXPRESSIONS && !defined(META_WORKAROUND_GCC_UNKNOWN1)
template <bool... Bs>
META_INLINE_VAR constexpr bool and_v = (true && ... && Bs);
/// Logically AND together all the Boolean parameters
/// \ingroup logical
template <bool... Bs>
#if defined(META_WORKAROUND_MSVC_756112) || defined(META_WORKAROUND_GCC_86356)
using and_c = bool_<and_v<Bs...>>;
#else
using and_c = bool_<(true && ... && Bs)>;
#endif
#else
#if defined(META_WORKAROUND_GCC_66405)
template <bool... Bs>
using and_c = meta::bool_<
META_IS_SAME(integer_sequence<bool, true, Bs...>,
integer_sequence<bool, Bs..., true>)>;
#else
template <bool... Bs>
struct and_c
: meta::bool_<
META_IS_SAME(integer_sequence<bool, Bs...>,
integer_sequence<bool, (Bs || true)...>)>
{};
#endif
#if META_CXX_VARIABLE_TEMPLATES
template <bool... Bs>
META_INLINE_VAR constexpr bool and_v =
META_IS_SAME(integer_sequence<bool, Bs...>,
integer_sequence<bool, (Bs || true)...>);
#endif
#endif
/// Logically AND together all the integral constant-wrapped Boolean
/// parameters, \e without short-circuiting.
/// \ingroup logical
template <META_TYPE_CONSTRAINT(integral)... Bs>
using strict_and_ = and_c<Bs::type::value...>;
template <typename... Bs>
using strict_and = strict_and_<Bs...>;
/// Logically AND together all the integral constant-wrapped Boolean
/// parameters, \e with short-circuiting.
/// \ingroup logical
template <typename... Bs>
#ifdef META_CONCEPT
using and_ = _t<detail::_and_<Bs...>>;
#else
// Make a trip through defer<> to avoid CWG1430
// https://wg21.link/cwg1430
using and_ = _t<defer<detail::_and_<0 == sizeof...(Bs)>::template invoke, Bs...>>;
#endif
/// Logically OR together all the Boolean parameters
/// \ingroup logical
#if META_CXX_FOLD_EXPRESSIONS && !defined(META_WORKAROUND_GCC_UNKNOWN1)
template <bool... Bs>
META_INLINE_VAR constexpr bool or_v = (false || ... || Bs);
template <bool... Bs>
#if defined(META_WORKAROUND_MSVC_756112) || defined(META_WORKAROUND_GCC_86356)
using or_c = bool_<or_v<Bs...>>;
#else
using or_c = bool_<(false || ... || Bs)>;
#endif
#else
template <bool... Bs>
struct or_c
: meta::bool_<
!META_IS_SAME(integer_sequence<bool, Bs...>,
integer_sequence<bool, (Bs && false)...>)>
{};
#if META_CXX_VARIABLE_TEMPLATES
template <bool... Bs>
META_INLINE_VAR constexpr bool or_v =
!META_IS_SAME(integer_sequence<bool, Bs...>,
integer_sequence<bool, (Bs && false)...>);
#endif
#endif
/// Logically OR together all the integral constant-wrapped Boolean
/// parameters, \e without short-circuiting.
/// \ingroup logical
template <META_TYPE_CONSTRAINT(integral)... Bs>
using strict_or_ = or_c<Bs::type::value...>;
template <typename... Bs>
using strict_or = strict_or_<Bs...>;
/// Logically OR together all the integral constant-wrapped Boolean
/// parameters, \e with short-circuiting.
/// \ingroup logical
template <typename... Bs>
#ifdef META_CONCEPT
using or_ = _t<detail::_or_<Bs...>>;
#else
// Make a trip through defer<> to avoid CWG1430
// https://wg21.link/cwg1430
using or_ = _t<defer<detail::_or_<0 == sizeof...(Bs)>::template invoke, Bs...>>;
#endif
namespace lazy
{
/// \sa 'meta::and_'
/// \ingroup lazy_logical
template <typename... Bs>
using and_ = defer<and_, Bs...>;
/// \sa 'meta::or_'
/// \ingroup lazy_logical
template <typename... Bs>
using or_ = defer<or_, Bs...>;
/// \sa 'meta::not_'
/// \ingroup lazy_logical
template <typename B>
using not_ = defer<not_, B>;
/// \sa 'meta::strict_and'
/// \ingroup lazy_logical
template <typename... Bs>
using strict_and = defer<strict_and, Bs...>;
/// \sa 'meta::strict_or'
/// \ingroup lazy_logical
template <typename... Bs>
using strict_or = defer<strict_or, Bs...>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// fold
/// \cond
namespace detail
{
template <typename, typename, typename>
struct fold_
{
};
template <typename Fn, typename T0, typename T1, typename T2, typename T3, typename T4,
typename T5, typename T6, typename T7, typename T8, typename T9>
struct compose10_
{
template <typename X, typename Y>
using F = invoke<Fn, X, Y>;
template <typename S>
using invoke =
F<F<F<F<F<F<F<F<F<F<_t<S>, T0>, T1>, T2>, T3>, T4>, T5>, T6>, T7>, T8>, T9>;
};
#ifdef META_CONCEPT
template <typename Fn>
struct compose_
{
template <typename X, typename Y>
using F = invoke<Fn, X, Y>;
template <typename T0, typename T1, typename T2, typename T3, typename T4,
typename T5, typename T6, typename T7, typename T8, typename T9,
typename State>
using invoke =
F<F<F<F<F<F<F<F<F<F<State, T0>, T1>, T2>, T3>, T4>, T5>, T6>, T7>, T8>, T9>;
};
template <typename State, typename Fn>
struct fold_<list<>, State, Fn>
{
using type = State;
};
template <typename Head, typename... Tail, typename State, typename Fn>
requires valid<invoke, Fn, State, Head>
struct fold_<list<Head, Tail...>, State, Fn>
: fold_<list<Tail...>, invoke<Fn, State, Head>, Fn>
{
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5,
typename T6, typename T7, typename T8, typename T9, typename... Tail,
typename State, typename Fn>
requires valid<invoke, compose_<Fn>, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, State>
struct fold_<list<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, Tail...>, State, Fn>
: fold_<list<Tail...>,
invoke<compose_<Fn>, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, State>, Fn>
{
};
#else // ^^^ Concepts / no Concepts vvv
template <typename Fn, typename T0>
struct compose1_
{
template <typename X>
using invoke = invoke<Fn, _t<X>, T0>;
};
template <typename State, typename Fn>
struct fold_<list<>, State, Fn> : State
{
};
template <typename Head, typename... Tail, typename State, typename Fn>
struct fold_<list<Head, Tail...>, State, Fn>
: fold_<list<Tail...>, lazy::invoke<compose1_<Fn, Head>, State>, Fn>
{
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5,
typename T6, typename T7, typename T8, typename T9, typename... Tail,
typename State, typename Fn>
struct fold_<list<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, Tail...>, State, Fn>
: fold_<list<Tail...>,
lazy::invoke<compose10_<Fn, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>, State>, Fn>
{
};
#endif // META_CONCEPT
} // namespace detail
/// \endcond
/// Return a new \c meta::list constructed by doing a left fold of the list \p L using
/// binary invocable \p Fn and initial state \p State. That is, the \c State_N for
/// the list element \c A_N is computed by `Fn(State_N-1, A_N) -> State_N`.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename State, META_TYPE_CONSTRAINT(invocable) Fn>
#ifdef META_CONCEPT
using fold = _t<detail::fold_<L, State, Fn>>;
#else
using fold = _t<detail::fold_<L, id<State>, Fn>>;
#endif
/// An alias for `meta::fold`.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename State, META_TYPE_CONSTRAINT(invocable) Fn>
using accumulate = fold<L, State, Fn>;
namespace lazy
{
/// \sa 'meta::foldl'
/// \ingroup lazy_transformation
template <typename L, typename State, typename Fn>
using fold = defer<fold, L, State, Fn>;
/// \sa 'meta::accumulate'
/// \ingroup lazy_transformation
template <typename L, typename State, typename Fn>
using accumulate = defer<accumulate, L, State, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// reverse_fold
/// \cond
namespace detail
{
template <typename, typename, typename>
struct reverse_fold_
{
};
template <typename State, typename Fn>
struct reverse_fold_<list<>, State, Fn>
{
using type = State;
};
#ifdef META_CONCEPT
template <typename Head, typename... L, typename State, typename Fn>
requires trait<reverse_fold_<list<L...>, State, Fn>> struct reverse_fold_<
list<Head, L...>, State, Fn>
: lazy::invoke<Fn, _t<reverse_fold_<list<L...>, State, Fn>>, Head>
{
};
#else
template <typename Head, typename... Tail, typename State, typename Fn>
struct reverse_fold_<list<Head, Tail...>, State, Fn>
: lazy::invoke<compose1_<Fn, Head>, reverse_fold_<list<Tail...>, State, Fn>>
{
};
#endif
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5,
typename T6, typename T7, typename T8, typename T9, typename... Tail,
typename State, typename Fn>
struct reverse_fold_<list<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, Tail...>, State, Fn>
: lazy::invoke<compose10_<Fn, T9, T8, T7, T6, T5, T4, T3, T2, T1, T0>,
reverse_fold_<list<Tail...>, State, Fn>>
{
};
} // namespace detail
/// \endcond
/// Return a new \c meta::list constructed by doing a right fold of the list \p L using
/// binary invocable \p Fn and initial state \p State. That is, the \c State_N for the list
/// element \c A_N is computed by `Fn(A_N, State_N+1) -> State_N`.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename State, META_TYPE_CONSTRAINT(invocable) Fn>
using reverse_fold = _t<detail::reverse_fold_<L, State, Fn>>;
namespace lazy
{
/// \sa 'meta::foldr'
/// \ingroup lazy_transformation
template <typename L, typename State, typename Fn>
using reverse_fold = defer<reverse_fold, L, State, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// npos
/// A special value used to indicate no matches. It equals the maximum
/// value representable by std::size_t.
/// \ingroup list
using npos = meta::size_t<std::size_t(-1)>;
///////////////////////////////////////////////////////////////////////////////////////////
// list
/// A list of types.
/// \ingroup list
template <typename... Ts>
struct list
{
using type = list;
/// \return `sizeof...(Ts)`
static constexpr std::size_t size() noexcept { return sizeof...(Ts); }
};
///////////////////////////////////////////////////////////////////////////////////////////
// size
/// An integral constant wrapper that is the size of the \c meta::list
/// \p L.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L>
using size = meta::size_t<L::size()>;
namespace lazy
{
/// \sa 'meta::size'
/// \ingroup lazy_list
template <typename L>
using size = defer<size, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// concat
/// \cond
namespace detail
{
template <typename... Lists>
struct concat_
{
};
template <>
struct concat_<>
{
using type = list<>;
};
template <typename... L1>
struct concat_<list<L1...>>
{
using type = list<L1...>;
};
template <typename... L1, typename... L2>
struct concat_<list<L1...>, list<L2...>>
{
using type = list<L1..., L2...>;
};
template <typename... L1, typename... L2, typename... L3>
struct concat_<list<L1...>, list<L2...>, list<L3...>>
{
using type = list<L1..., L2..., L3...>;
};
template <typename... L1, typename... L2, typename... L3, typename... Rest>
struct concat_<list<L1...>, list<L2...>, list<L3...>, Rest...>
: concat_<list<L1..., L2..., L3...>, Rest...>
{
};
template <typename... L1, typename... L2, typename... L3, typename... L4,
typename... L5, typename... L6, typename... L7, typename... L8,
typename... L9, typename... L10, typename... Rest>
struct concat_<list<L1...>, list<L2...>, list<L3...>, list<L4...>, list<L5...>,
list<L6...>, list<L7...>, list<L8...>, list<L9...>, list<L10...>,
Rest...>
: concat_<list<L1..., L2..., L3..., L4..., L5..., L6..., L7..., L8..., L9..., L10...>,
Rest...>
{
};
} // namespace detail
/// \endcond
/// Concatenates several lists into a single list.
/// \pre The parameters must all be instantiations of \c meta::list.
/// \par Complexity
/// \f$ O(L) \f$ where \f$ L \f$ is the number of lists in the list of lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like)... Ls>
using concat_ = _t<detail::concat_<Ls...>>;
template <typename... Lists>
using concat = concat_<Lists...>;
namespace lazy
{
/// \sa 'meta::concat'
/// \ingroup lazy_transformation
template <typename... Lists>
using concat = defer<concat, Lists...>;
} // namespace lazy
/// Joins a list of lists into a single list.
/// \pre The parameter must be an instantiation of \c meta::list\<T...\>
/// where each \c T is itself an instantiation of \c meta::list.
/// \par Complexity
/// \f$ O(L) \f$ where \f$ L \f$ is the number of lists in the list of
/// lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) ListOfLists>
using join = apply<quote<concat>, ListOfLists>;
namespace lazy
{
/// \sa 'meta::join'
/// \ingroup lazy_transformation
template <typename ListOfLists>
using join = defer<join, ListOfLists>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// transform
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename... Args>
struct transform_
{
};
template <typename... Ts, typename Fn>
requires invocable<Fn> && and_v<valid<invoke, Fn, Ts>...>
struct transform_<list<Ts...>, Fn>
{
using type = list<invoke<Fn, Ts>...>;
};
template <typename... Ts, typename... Us, typename Fn>
requires invocable<Fn> && and_v<valid<invoke, Fn, Ts, Us>...>
struct transform_<list<Ts...>, list<Us...>, Fn>
{
using type = list<invoke<Fn, Ts, Us>...>;
};
#else
template <typename, typename = void>
struct transform_
{
};
template <typename... Ts, typename Fn>
struct transform_<list<list<Ts...>, Fn>, void_<invoke<Fn, Ts>...>>
{
using type = list<invoke<Fn, Ts>...>;
};
template <typename... Ts0, typename... Ts1, typename Fn>
struct transform_<list<list<Ts0...>, list<Ts1...>, Fn>,
void_<invoke<Fn, Ts0, Ts1>...>>
{
using type = list<invoke<Fn, Ts0, Ts1>...>;
};
#endif
} // namespace detail
/// \endcond
/// Return a new \c meta::list constructed by transforming all the
/// elements in \p L with the unary invocable \p Fn. \c transform can
/// also be called with two lists of the same length and a binary
/// invocable, in which case it returns a new list constructed with the
/// results of calling \c Fn with each element in the lists, pairwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
#ifdef META_CONCEPT
template <typename... Args>
using transform = _t<detail::transform_<Args...>>;
#else
template <typename... Args>
using transform = _t<detail::transform_<list<Args...>>>;
#endif
namespace lazy
{
/// \sa 'meta::transform'
/// \ingroup lazy_transformation
template <typename... Args>
using transform = defer<transform, Args...>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// repeat_n
/// \cond
namespace detail
{
template <typename T, std::size_t>
using first_ = T;
template <typename T, typename Ints>
struct repeat_n_c_
{
};
template <typename T, std::size_t... Is>
struct repeat_n_c_<T, index_sequence<Is...>>
{
using type = list<first_<T, Is>...>;
};
} // namespace detail
/// \endcond
/// Generate `list<T,T,T...T>` of size \p N arguments.
/// \par Complexity
/// \f$ O(log N) \f$.
/// \ingroup list
template <std::size_t N, typename T = void>
using repeat_n_c = _t<detail::repeat_n_c_<T, make_index_sequence<N>>>;
/// Generate `list<T,T,T...T>` of size \p N arguments.
/// \par Complexity
/// \f$ O(log N) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(integral) N, typename T = void>
using repeat_n = repeat_n_c<N::type::value, T>;
namespace lazy
{
/// \sa 'meta::repeat_n'
/// \ingroup lazy_list
template <typename N, typename T = void>
using repeat_n = defer<repeat_n, N, T>;
/// \sa 'meta::repeat_n_c'
/// \ingroup lazy_list
template <std::size_t N, typename T = void>
using repeat_n_c = defer<repeat_n, meta::size_t<N>, T>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// at
/// \cond
namespace detail
{
#if META_HAS_TYPE_PACK_ELEMENT && !defined(META_DOXYGEN_INVOKED)
template <typename L, std::size_t N, typename = void>
struct at_
{
};
template <typename... Ts, std::size_t N>
struct at_<list<Ts...>, N, void_<__type_pack_element<N, Ts...>>>
{
using type = __type_pack_element<N, Ts...>;
};
#else
template <typename VoidPtrs>
struct at_impl_;
template <typename... VoidPtrs>
struct at_impl_<list<VoidPtrs...>>
{
static nil_ eval(...);
template <typename T, typename... Us>
static T eval(VoidPtrs..., T *, Us *...);
};
template <typename L, std::size_t N>
struct at_
{
};
template <typename... Ts, std::size_t N>
struct at_<list<Ts...>, N>
: decltype(at_impl_<repeat_n_c<N, void *>>::eval(static_cast<id<Ts> *>(nullptr)...))
{
};
#endif // META_HAS_TYPE_PACK_ELEMENT
} // namespace detail
/// \endcond
/// Return the \p N th element in the \c meta::list \p L.
/// \par Complexity
/// Amortized \f$ O(1) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L, std::size_t N>
using at_c = _t<detail::at_<L, N>>;
/// Return the \p N th element in the \c meta::list \p L.
/// \par Complexity
/// Amortized \f$ O(1) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(integral) N>
using at = at_c<L, N::type::value>;
namespace lazy
{
/// \sa 'meta::at'
/// \ingroup lazy_list
template <typename L, typename N>
using at = defer<at, L, N>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// drop
/// \cond
namespace detail
{
///////////////////////////////////////////////////////////////////////////////////////
/// drop_impl_
template <typename VoidPtrs>
struct drop_impl_
{
static nil_ eval(...);
};
template <typename... VoidPtrs>
struct drop_impl_<list<VoidPtrs...>>
{
static nil_ eval(...);
template <typename... Ts>
static id<list<Ts...>> eval(VoidPtrs..., id<Ts> *...);
};
template <>
struct drop_impl_<list<>>
{
template <typename... Ts>
static id<list<Ts...>> eval(id<Ts> *...);
};
template <typename L, std::size_t N>
struct drop_
{
};
template <typename... Ts, std::size_t N>
struct drop_<list<Ts...>, N>
#if META_CXX_VARIABLE_TEMPLATES
: decltype(drop_impl_<repeat_n_c<N, void *>>::eval(detail::nullptr_v<id<Ts>>...))
#else
: decltype(drop_impl_<repeat_n_c<N, void *>>::eval(detail::_nullptr_v<id<Ts>>()...))
#endif
{
};
} // namespace detail
/// \endcond
/// Return a new \c meta::list by removing the first \p N elements from \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, std::size_t N>
using drop_c = _t<detail::drop_<L, N>>;
/// Return a new \c meta::list by removing the first \p N elements from \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(integral) N>
using drop = drop_c<L, N::type::value>;
namespace lazy
{
/// \sa 'meta::drop'
/// \ingroup lazy_transformation
template <typename L, typename N>
using drop = defer<drop, L, N>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// front
/// \cond
namespace detail
{
template <typename L>
struct front_
{
};
template <typename Head, typename... Tail>
struct front_<list<Head, Tail...>>
{
using type = Head;
};
} // namespace detail
/// \endcond
/// Return the first element in \c meta::list \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L>
using front = _t<detail::front_<L>>;
namespace lazy
{
/// \sa 'meta::front'
/// \ingroup lazy_list
template <typename L>
using front = defer<front, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// back
/// \cond
namespace detail
{
template <typename L>
struct back_
{
};
template <typename Head, typename... Tail>
struct back_<list<Head, Tail...>>
{
using type = at_c<list<Head, Tail...>, sizeof...(Tail)>;
};
} // namespace detail
/// \endcond
/// Return the last element in \c meta::list \p L.
/// \par Complexity
/// Amortized \f$ O(1) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L>
using back = _t<detail::back_<L>>;
namespace lazy
{
/// \sa 'meta::back'
/// \ingroup lazy_list
template <typename L>
using back = defer<back, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// push_front
/// Return a new \c meta::list by adding the element \c T to the front of \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename... Ts>
using push_front = apply<bind_front<quote<list>, Ts...>, L>;
namespace lazy
{
/// \sa 'meta::push_front'
/// \ingroup lazy_transformation
template <typename... Ts>
using push_front = defer<push_front, Ts...>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// pop_front
/// \cond
namespace detail
{
template <typename L>
struct pop_front_
{
};
template <typename Head, typename... L>
struct pop_front_<list<Head, L...>>
{
using type = list<L...>;
};
} // namespace detail
/// \endcond
/// Return a new \c meta::list by removing the first element from the
/// front of \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L>
using pop_front = _t<detail::pop_front_<L>>;
namespace lazy
{
/// \sa 'meta::pop_front'
/// \ingroup lazy_transformation
template <typename L>
using pop_front = defer<pop_front, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// push_back
/// Return a new \c meta::list by adding the element \c T to the back of \p L.
/// \par Complexity
/// \f$ O(1) \f$.
/// \note \c pop_back not provided because it cannot be made to meet the
/// complexity guarantees one would expect.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename... Ts>
using push_back = apply<bind_back<quote<list>, Ts...>, L>;
namespace lazy
{
/// \sa 'meta::push_back'
/// \ingroup lazy_transformation
template <typename... Ts>
using push_back = defer<push_back, Ts...>;
} // namespace lazy
/// \cond
namespace detail
{
template <typename T, typename U>
using min_ = if_<less<U, T>, U, T>;
template <typename T, typename U>
using max_ = if_<less<U, T>, T, U>;
} // namespace detail
/// \endcond
/// An integral constant wrapper around the minimum of `Ts::type::value...`
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral)... Ts>
using min_ = fold<pop_front<list<Ts...>>, front<list<Ts...>>, quote<detail::min_>>;
template <typename... Ts>
using min = min_<Ts...>;
/// An integral constant wrapper around the maximum of `Ts::type::value...`
/// \ingroup math
template <META_TYPE_CONSTRAINT(integral)... Ts>
using max_ = fold<pop_front<list<Ts...>>, front<list<Ts...>>, quote<detail::max_>>;
template <typename... Ts>
using max = max_<Ts...>;
namespace lazy
{
/// \sa 'meta::min'
/// \ingroup lazy_math
template <typename... Ts>
using min = defer<min, Ts...>;
/// \sa 'meta::max'
/// \ingroup lazy_math
template <typename... Ts>
using max = defer<max, Ts...>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// empty
/// An Boolean integral constant wrapper around \c true if \p L is an
/// empty type list; \c false, otherwise.
/// \par Complexity
/// \f$ O(1) \f$.
/// \ingroup list
template <META_TYPE_CONSTRAINT(list_like) L>
using empty = bool_<0 == size<L>::type::value>;
namespace lazy
{
/// \sa 'meta::empty'
/// \ingroup lazy_list
template <typename L>
using empty = defer<empty, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// pair
/// A list with exactly two elements
/// \ingroup list
template <typename F, typename S>
using pair = list<F, S>;
/// Retrieve the first element of the \c pair \p Pair
/// \ingroup list
template <typename Pair>
using first = front<Pair>;
/// Retrieve the first element of the \c pair \p Pair
/// \ingroup list
template <typename Pair>
using second = front<pop_front<Pair>>;
namespace lazy
{
/// \sa 'meta::first'
/// \ingroup lazy_list
template <typename Pair>
using first = defer<first, Pair>;
/// \sa 'meta::second'
/// \ingroup lazy_list
template <typename Pair>
using second = defer<second, Pair>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// find_index
/// \cond
namespace detail
{
// With thanks to Peter Dimov:
constexpr std::size_t find_index_i_(bool const *const first, bool const *const last,
std::size_t N = 0)
{
return first == last ? npos::value
: *first ? N : find_index_i_(first + 1, last, N + 1);
}
template <typename L, typename T>
struct find_index_
{
};
template <typename V>
struct find_index_<list<>, V>
{
using type = npos;
};
template <typename... T, typename V>
struct find_index_<list<T...>, V>
{
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(T)] = {META_IS_SAME(T, V)...};
#else
static constexpr bool s_v[] = {META_IS_SAME(T, V)...};
#endif
using type = size_t<find_index_i_(s_v, s_v + sizeof...(T))>;
};
} // namespace detail
/// \endcond
/// Finds the index of the first occurrence of the type \p T within the list \p L.
/// Returns `#meta::npos` if the type \p T was not found.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
/// \sa `meta::npos`
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using find_index = _t<detail::find_index_<L, T>>;
namespace lazy
{
/// \sa 'meta::find_index'
/// \ingroup lazy_query
template <typename L, typename T>
using find_index = defer<find_index, L, T>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// reverse_find_index
/// \cond
namespace detail
{
// With thanks to Peter Dimov:
constexpr std::size_t reverse_find_index_i_(bool const *const first,
bool const *const last, std::size_t N)
{
return first == last
? npos::value
: *(last - 1) ? N - 1 : reverse_find_index_i_(first, last - 1, N - 1);
}
template <typename L, typename T>
struct reverse_find_index_
{
};
template <typename V>
struct reverse_find_index_<list<>, V>
{
using type = npos;
};
template <typename... T, typename V>
struct reverse_find_index_<list<T...>, V>
{
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(T)] = {META_IS_SAME(T, V)...};
#else
static constexpr bool s_v[] = {META_IS_SAME(T, V)...};
#endif
using type = size_t<reverse_find_index_i_(s_v, s_v + sizeof...(T), sizeof...(T))>;
};
} // namespace detail
/// \endcond
/// Finds the index of the last occurrence of the type \p T within the
/// list \p L. Returns `#meta::npos` if the type \p T was not found.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
/// \sa `#meta::npos`
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using reverse_find_index = _t<detail::reverse_find_index_<L, T>>;
namespace lazy
{
/// \sa 'meta::reverse_find_index'
/// \ingroup lazy_query
template <typename L, typename T>
using reverse_find_index = defer<reverse_find_index, L, T>;
} // namespace lazy
////////////////////////////////////////////////////////////////////////////////////
// find
/// Return the tail of the list \p L starting at the first occurrence of
/// \p T, if any such element exists; the empty list, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using find = drop<L, min<find_index<L, T>, size<L>>>;
namespace lazy
{
/// \sa 'meta::find'
/// \ingroup lazy_query
template <typename L, typename T>
using find = defer<find, L, T>;
} // namespace lazy
////////////////////////////////////////////////////////////////////////////////////
// reverse_find
/// \cond
namespace detail
{
template <typename L, typename T, typename State = list<>>
struct reverse_find_
{
};
template <typename T, typename State>
struct reverse_find_<list<>, T, State>
{
using type = State;
};
template <typename Head, typename... L, typename T, typename State>
struct reverse_find_<list<Head, L...>, T, State> : reverse_find_<list<L...>, T, State>
{
};
template <typename... L, typename T, typename State>
struct reverse_find_<list<T, L...>, T, State>
: reverse_find_<list<L...>, T, list<T, L...>>
{
};
} // namespace detail
/// \endcond
/// Return the tail of the list \p L starting at the last occurrence of \p T, if any such
/// element exists; the empty list, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using reverse_find = drop<L, min<reverse_find_index<L, T>, size<L>>>;
namespace lazy
{
/// \sa 'meta::rfind'
/// \ingroup lazy_query
template <typename L, typename T>
using reverse_find = defer<reverse_find, L, T>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// find_if
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename L, typename Fn>
struct find_if_
{
};
template <typename Fn>
struct find_if_<list<>, Fn>
{
using type = list<>;
};
template <typename Head, typename... L, typename Fn>
requires integral<invoke<Fn, Head>>
struct find_if_<list<Head, L...>, Fn>
: if_<invoke<Fn, Head>, id<list<Head, L...>>, find_if_<list<L...>, Fn>>
{
};
#else
constexpr bool const *find_if_i_(bool const *const begin, bool const *const end)
{
return begin == end || *begin ? begin : find_if_i_(begin + 1, end);
}
template <typename L, typename Fn, typename = void>
struct find_if_
{
};
template <typename Fn>
struct find_if_<list<>, Fn>
{
using type = list<>;
};
template <typename... L, typename Fn>
struct find_if_<list<L...>, Fn,
void_<integer_sequence<bool, bool(invoke<Fn, L>::type::value)...>>>
{
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(L)] = {invoke<Fn, L>::type::value...};
#else
static constexpr bool s_v[] = {invoke<Fn, L>::type::value...};
#endif
using type =
drop_c<list<L...>, detail::find_if_i_(s_v, s_v + sizeof...(L)) - s_v>;
};
#endif
} // namespace detail
/// \endcond
/// Return the tail of the list \p L starting at the first element `A`
/// such that `invoke<Fn, A>::%value` is \c true, if any such element
/// exists; the empty list, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using find_if = _t<detail::find_if_<L, Fn>>;
namespace lazy
{
/// \sa 'meta::find_if'
/// \ingroup lazy_query
template <typename L, typename Fn>
using find_if = defer<find_if, L, Fn>;
} // namespace lazy
////////////////////////////////////////////////////////////////////////////////////
// reverse_find_if
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename L, typename Fn, typename State = list<>>
struct reverse_find_if_
{
};
template <typename Fn, typename State>
struct reverse_find_if_<list<>, Fn, State>
{
using type = State;
};
template <typename Head, typename... L, typename Fn, typename State>
requires integral<invoke<Fn, Head>>
struct reverse_find_if_<list<Head, L...>, Fn, State>
: reverse_find_if_<list<L...>, Fn, if_<invoke<Fn, Head>, list<Head, L...>, State>>
{
};
#else
constexpr bool const *reverse_find_if_i_(bool const *const begin, bool const *const pos,
bool const *const end)
{
return begin == pos
? end
: *(pos - 1) ? pos - 1 : reverse_find_if_i_(begin, pos - 1, end);
}
template <typename L, typename Fn, typename = void>
struct reverse_find_if_
{
};
template <typename Fn>
struct reverse_find_if_<list<>, Fn>
{
using type = list<>;
};
template <typename... L, typename Fn>
struct reverse_find_if_<
list<L...>, Fn,
void_<integer_sequence<bool, bool(invoke<Fn, L>::type::value)...>>>
{
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(L)] = {invoke<Fn, L>::type::value...};
#else
static constexpr bool s_v[] = {invoke<Fn, L>::type::value...};
#endif
using type =
drop_c<list<L...>, detail::reverse_find_if_i_(s_v, s_v + sizeof...(L),
s_v + sizeof...(L)) -
s_v>;
};
#endif
} // namespace detail
/// \endcond
/// Return the tail of the list \p L starting at the last element `A`
/// such that `invoke<Fn, A>::%value` is \c true, if any such element
/// exists; the empty list, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using reverse_find_if = _t<detail::reverse_find_if_<L, Fn>>;
namespace lazy
{
/// \sa 'meta::rfind_if'
/// \ingroup lazy_query
template <typename L, typename Fn>
using reverse_find_if = defer<reverse_find_if, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// replace
/// \cond
namespace detail
{
template <typename L, typename T, typename U>
struct replace_
{
};
template <typename... L, typename T, typename U>
struct replace_<list<L...>, T, U>
{
using type = list<if_c<META_IS_SAME(T, L), U, L>...>;
};
} // namespace detail
/// \endcond
/// Return a new \c meta::list where all instances of type \p T have
/// been replaced with \p U.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename T, typename U>
using replace = _t<detail::replace_<L, T, U>>;
namespace lazy
{
/// \sa 'meta::replace'
/// \ingroup lazy_transformation
template <typename L, typename T, typename U>
using replace = defer<replace, T, U>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// replace_if
/// \cond
namespace detail
{
#ifdef META_CONCEPT
template <typename L, typename C, typename U>
struct replace_if_
{
};
template <typename... L, typename C, typename U>
requires and_v<integral<invoke<C, L>>...>
struct replace_if_<list<L...>, C, U>
{
using type = list<if_<invoke<C, L>, U, L>...>;
};
#else
template <typename L, typename C, typename U, typename = void>
struct replace_if_
{
};
template <typename... L, typename C, typename U>
struct replace_if_<list<L...>, C, U,
void_<integer_sequence<bool, bool(invoke<C, L>::type::value)...>>>
{
using type = list<if_<invoke<C, L>, U, L>...>;
};
#endif
} // namespace detail
/// \endcond
/// Return a new \c meta::list where all elements \c A of the list \p L
/// for which `invoke<C,A>::%value` is \c true have been replaced with
/// \p U.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, typename C, typename U>
using replace_if = _t<detail::replace_if_<L, C, U>>;
namespace lazy
{
/// \sa 'meta::replace_if'
/// \ingroup lazy_transformation
template <typename L, typename C, typename U>
using replace_if = defer<replace_if, C, U>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////
// count
namespace detail
{
template <typename, typename>
struct count_
{
};
#if (defined(META_CONCEPT) || META_CXX_VARIABLE_TEMPLATES) && META_CXX_FOLD_EXPRESSIONS
template <typename... Ts, typename T>
struct count_<list<Ts...>, T>
{
using type = meta::size_t<((std::size_t)META_IS_SAME(T, Ts) + ...)>;
};
#else
constexpr std::size_t count_i_(bool const *const begin, bool const *const end,
std::size_t n)
{
return begin == end ? n : detail::count_i_(begin + 1, end, n + *begin);
}
template <typename T>
struct count_<list<>, T>
{
using type = meta::size_t<0>;
};
template <typename... L, typename T>
struct count_<list<L...>, T>
{
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(L)] = {META_IS_SAME(T, L)...};
#else
static constexpr bool s_v[] = {META_IS_SAME(T, L)...};
#endif
using type = meta::size_t<detail::count_i_(s_v, s_v + sizeof...(L), 0u)>;
};
#endif
} // namespace detail
/// Count the number of times a type \p T appears in the list \p L.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using count = _t<detail::count_<L, T>>;
namespace lazy
{
/// \sa `meta::count`
/// \ingroup lazy_query
template <typename L, typename T>
using count = defer<count, L, T>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////
// count_if
namespace detail
{
#if defined(META_CONCEPT) && META_CXX_FOLD_EXPRESSIONS
template <typename, typename>
struct count_if_
{
};
template <typename... Ts, typename Fn>
requires (integral<invoke<Fn, Ts>> && ...)
struct count_if_<list<Ts...>, Fn>
{
using type = meta::size_t<((std::size_t)(bool)_v<invoke<Fn, Ts>> + ...)>;
};
#else
template <typename L, typename Fn, typename = void>
struct count_if_
{
};
template <typename Fn>
struct count_if_<list<>, Fn>
{
using type = meta::size_t<0>;
};
template <typename... L, typename Fn>
struct count_if_<list<L...>, Fn,
void_<integer_sequence<bool, bool(invoke<Fn, L>::type::value)...>>>
{
#if META_CXX_FOLD_EXPRESSIONS
using type = meta::size_t<((std::size_t)(bool)invoke<Fn, L>::type::value + ...)>;
#else
#ifdef META_WORKAROUND_LLVM_28385
static constexpr bool s_v[sizeof...(L)] = {invoke<Fn, L>::type::value...};
#else
static constexpr bool s_v[] = {invoke<Fn, L>::type::value...};
#endif
using type = meta::size_t<detail::count_i_(s_v, s_v + sizeof...(L), 0u)>;
#endif // META_CXX_FOLD_EXPRESSIONS
};
#endif // META_CONCEPT
} // namespace detail
/// Count the number of times the predicate \p Fn evaluates to true for all the elements in
/// the list \p L.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using count_if = _t<detail::count_if_<L, Fn>>;
namespace lazy
{
/// \sa `meta::count_if`
/// \ingroup lazy_query
template <typename L, typename Fn>
using count_if = defer<count_if, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// filter
/// \cond
namespace detail
{
template <typename Pred>
struct filter_
{
template <typename A>
using invoke = if_c<invoke<Pred, A>::type::value, list<A>, list<>>;
};
} // namespace detail
/// \endcond
/// Returns a new meta::list where only those elements of \p L that satisfy the
/// Callable \p Pred such that `invoke<Pred,A>::%value` is \c true are present.
/// That is, those elements that don't satisfy the \p Pred are "removed".
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <typename L, typename Pred>
using filter = join<transform<L, detail::filter_<Pred>>>;
namespace lazy
{
/// \sa 'meta::filter'
/// \ingroup lazy_transformation
template <typename L, typename Fn>
using filter = defer<filter, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// static_const
///\cond
namespace detail
{
template <typename T>
struct static_const
{
static constexpr T value{};
};
// Avoid potential ODR violations with global objects:
template <typename T>
constexpr T static_const<T>::value;
} // namespace detail
///\endcond
///////////////////////////////////////////////////////////////////////////////////////////
// for_each
/// \cond
namespace detail
{
struct for_each_fn
{
template <class Fn, class... Args>
constexpr auto operator()(list<Args...>, Fn f) const -> Fn
{
return (void)std::initializer_list<int>{((void)f(Args{}), 0)...}, f;
}
};
} // namespace detail
/// \endcond
#if META_CXX_INLINE_VARIABLES
/// `for_each(L, Fn)` calls the \p Fn for each
/// argument in the \p L.
/// \ingroup runtime
inline constexpr detail::for_each_fn for_each{};
#else
///\cond
namespace
{
/// \endcond
/// `for_each(List, UnaryFunction)` calls the \p UnaryFunction for each
/// argument in the \p List.
/// \ingroup runtime
constexpr auto &&for_each = detail::static_const<detail::for_each_fn>::value;
/// \cond
}
/// \endcond
#endif
///////////////////////////////////////////////////////////////////////////////////////////
// transpose
/// Given a list of lists of types \p ListOfLists, transpose the elements from the lists.
/// \par Complexity
/// \f$ O(N \times M) \f$, where \f$ N \f$ is the size of the outer list, and
/// \f$ M \f$ is the size of the inner lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) ListOfLists>
using transpose = fold<ListOfLists, repeat_n<size<front<ListOfLists>>, list<>>,
bind_back<quote<transform>, quote<push_back>>>;
namespace lazy
{
/// \sa 'meta::transpose'
/// \ingroup lazy_transformation
template <typename ListOfLists>
using transpose = defer<transpose, ListOfLists>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// zip_with
/// Given a list of lists of types \p ListOfLists and an invocable \p Fn, construct a new
/// list by calling \p Fn with the elements from the lists pairwise.
/// \par Complexity
/// \f$ O(N \times M) \f$, where \f$ N \f$ is the size of the outer list, and
/// \f$ M \f$ is the size of the inner lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(invocable) Fn, META_TYPE_CONSTRAINT(list_like) ListOfLists>
using zip_with = transform<transpose<ListOfLists>, uncurry<Fn>>;
namespace lazy
{
/// \sa 'meta::zip_with'
/// \ingroup lazy_transformation
template <typename Fn, typename ListOfLists>
using zip_with = defer<zip_with, Fn, ListOfLists>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// zip
/// Given a list of lists of types \p ListOfLists, construct a new list by grouping the
/// elements from the lists pairwise into `meta::list`s.
/// \par Complexity
/// \f$ O(N \times M) \f$, where \f$ N \f$ is the size of the outer list, and \f$ M \f$
/// is the size of the inner lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) ListOfLists>
using zip = transpose<ListOfLists>;
namespace lazy
{
/// \sa 'meta::zip'
/// \ingroup lazy_transformation
template <typename ListOfLists>
using zip = defer<zip, ListOfLists>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// as_list
/// \cond
namespace detail
{
template <typename T>
using uncvref_t = _t<std::remove_cv<_t<std::remove_reference<T>>>>;
// Indirection here needed to avoid Core issue 1430
// https://wg21.link/cwg1430
template <typename Sequence>
struct as_list_ : lazy::invoke<uncurry<quote<list>>, Sequence>
{
};
} // namespace detail
/// \endcond
/// Turn a type into an instance of \c meta::list in a way determined by
/// \c meta::apply.
/// \ingroup list
template <typename Sequence>
using as_list = _t<detail::as_list_<detail::uncvref_t<Sequence>>>;
namespace lazy
{
/// \sa 'meta::as_list'
/// \ingroup lazy_list
template <typename Sequence>
using as_list = defer<as_list, Sequence>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// reverse
/// \cond
namespace detail
{
template <typename L, typename State = list<>>
struct reverse_ : lazy::fold<L, State, quote<push_front>>
{
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5,
typename T6, typename T7, typename T8, typename T9, typename... Ts,
typename... Us>
struct reverse_<list<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, Ts...>, list<Us...>>
: reverse_<list<Ts...>, list<T9, T8, T7, T6, T5, T4, T3, T2, T1, T0, Us...>>
{
};
}
/// \endcond
/// Return a new \c meta::list by reversing the elements in the list \p L.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L>
using reverse = _t<detail::reverse_<L>>;
namespace lazy
{
/// \sa 'meta::reverse'
/// \ingroup lazy_transformation
template <typename L>
using reverse = defer<reverse, L>;
} // namespace lazy
/// Logically negate the result of invocable \p Fn.
/// \ingroup trait
template <META_TYPE_CONSTRAINT(invocable) Fn>
using not_fn = compose<quote<not_>, Fn>;
namespace lazy
{
/// \sa 'meta::not_fn'
/// \ingroup lazy_trait
template <typename Fn>
using not_fn = defer<not_fn, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// all_of
/// A Boolean integral constant wrapper around \c true if `invoke<Fn, A>::%value` is \c true
/// for all elements \c A in \c meta::list \p L; \c false, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using all_of = empty<find_if<L, not_fn<Fn>>>;
namespace lazy
{
/// \sa 'meta::all_of'
/// \ingroup lazy_query
template <typename L, typename Fn>
using all_of = defer<all_of, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// any_of
/// A Boolean integral constant wrapper around \c true if `invoke<Fn, A>::%value` is
/// \c true for any element \c A in \c meta::list \p L; \c false, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using any_of = not_<empty<find_if<L, Fn>>>;
namespace lazy
{
/// \sa 'meta::any_of'
/// \ingroup lazy_query
template <typename L, typename Fn>
using any_of = defer<any_of, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// none_of
/// A Boolean integral constant wrapper around \c true if `invoke<Fn, A>::%value` is
/// \c false for all elements \c A in \c meta::list \p L; \c false, otherwise.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using none_of = empty<find_if<L, Fn>>;
namespace lazy
{
/// \sa 'meta::none_of'
/// \ingroup lazy_query
template <typename L, META_TYPE_CONSTRAINT(invocable) Fn>
using none_of = defer<none_of, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// in
/// A Boolean integral constant wrapper around \c true if there is at least one occurrence
/// of \p T in \p L.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup query
template <META_TYPE_CONSTRAINT(list_like) L, typename T>
using in = not_<empty<find<L, T>>>;
namespace lazy
{
/// \sa 'meta::in'
/// \ingroup lazy_query
template <typename L, typename T>
using in = defer<in, L, T>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// inherit
/// \cond
namespace detail
{
template <typename L>
struct inherit_
{
};
template <typename... L>
struct inherit_<list<L...>> : L...
{
using type = inherit_;
};
} // namespace detail
/// \endcond
/// A type that inherits from all the types in the list
/// \pre The types in the list must be unique
/// \pre All the types in the list must be non-final class types
/// \ingroup datatype
template <META_TYPE_CONSTRAINT(list_like) L>
using inherit = meta::_t<detail::inherit_<L>>;
namespace lazy
{
/// \sa 'meta::inherit'
/// \ingroup lazy_datatype
template <typename L>
using inherit = defer<inherit, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// unique
/// \cond
namespace detail
{
template <typename Set, typename T>
struct in_
{
};
template <typename... Set, typename T>
struct in_<list<Set...>, T> : bool_<META_IS_BASE_OF(id<T>, inherit<list<id<Set>...>>)>
{
};
template <typename Set, typename T>
struct insert_back_
{
};
template <typename... Set, typename T>
struct insert_back_<list<Set...>, T>
{
using type = if_<in_<list<Set...>, T>, list<Set...>, list<Set..., T>>;
};
} // namespace detail
/// \endcond
/// Return a new \c meta::list where all duplicate elements have been removed.
/// \par Complexity
/// \f$ O(N^2) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L>
using unique = fold<L, list<>, quote_trait<detail::insert_back_>>;
namespace lazy
{
/// \sa 'meta::unique'
/// \ingroup lazy_transformation
template <typename L>
using unique = defer<unique, L>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// partition
/// \cond
namespace detail
{
template <typename Fn>
struct partition_
{
#ifdef META_CONCEPT
template <typename, typename>
#else
template <typename, typename, typename = void>
#endif
struct impl
{
};
template <typename... Yes, typename... No, typename A>
#ifdef META_CONCEPT
requires integral<invoke<Fn, A>>
struct impl<pair<list<Yes...>, list<No...>>, A>
#else
struct impl<pair<list<Yes...>, list<No...>>, A,
void_<bool_<invoke<Fn, A>::type::value>>>
#endif
{
using type = if_<invoke<Fn, A>, pair<list<Yes..., A>, list<No...>>,
pair<list<Yes...>, list<No..., A>>>;
};
template <typename State, typename A>
using invoke = _t<impl<State, A>>;
};
} // namespace detail
/// \endcond
/// Returns a pair of lists, where the elements of \p L that satisfy the
/// invocable \p Fn such that `invoke<Fn,A>::%value` is \c true are present in the
/// first list and the rest are in the second.
/// \par Complexity
/// \f$ O(N) \f$.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using partition = fold<L, pair<list<>, list<>>, detail::partition_<Fn>>;
namespace lazy
{
/// \sa 'meta::partition'
/// \ingroup lazy_transformation
template <typename L, typename Fn>
using partition = defer<partition, L, Fn>;
} // namespace lazy
///////////////////////////////////////////////////////////////////////////////////////////
// sort
/// \cond
namespace detail
{
template <META_TYPE_CONSTRAINT(invocable) Fn, typename A, typename B, typename... Ts>
using part_ = partition<list<B, Ts...>, bind_back<Fn, A>>;
#ifdef META_CONCEPT
template <typename L, typename Fn>
requires list_like<L> && invocable<Fn>
#else
template <typename, typename, typename = void>
#endif
struct sort_
{
};
template <typename Fn>
struct sort_<list<>, Fn>
{
using type = list<>;
};
template <typename A, typename Fn>
struct sort_<list<A>, Fn>
{
using type = list<A>;
};
template <typename A, typename B, typename... Ts, typename Fn>
#ifdef META_CONCEPT
requires trait<sort_<first<part_<Fn, A, B, Ts...>>, Fn>> &&
trait<sort_<second<part_<Fn, A, B, Ts...>>, Fn>>
struct sort_<list<A, B, Ts...>, Fn>
#else
struct sort_<
list<A, B, Ts...>, Fn,
void_<_t<sort_<first<part_<Fn, A, B, Ts...>>, Fn>>>>
#endif
{
using P = part_<Fn, A, B, Ts...>;
using type = concat<_t<sort_<first<P>, Fn>>, list<A>, _t<sort_<second<P>, Fn>>>;
};
} // namespace detail
/// \endcond
// clang-format off
/// Return a new \c meta::list that is sorted according to invocable predicate \p Fn.
/// \par Complexity
/// Expected: \f$ O(N log N) \f$
/// Worst case: \f$ O(N^2) \f$.
/// \code
/// using L0 = list<char[5], char[3], char[2], char[6], char[1], char[5], char[10]>;
/// using L1 = meta::sort<L0, lambda<_a, _b, lazy::less<lazy::sizeof_<_a>, lazy::sizeof_<_b>>>>;
/// static_assert(std::is_same_v<L1, list<char[1], char[2], char[3], char[5], char[5], char[6], char[10]>>, "");
/// \endcode
/// \ingroup transformation
// clang-format on
template <META_TYPE_CONSTRAINT(list_like) L, META_TYPE_CONSTRAINT(invocable) Fn>
using sort = _t<detail::sort_<L, Fn>>;
namespace lazy
{
/// \sa 'meta::sort'
/// \ingroup lazy_transformation
template <typename L, typename Fn>
using sort = defer<sort, L, Fn>;
} // namespace lazy
////////////////////////////////////////////////////////////////////////////
// lambda_
/// \cond
namespace detail
{
template <typename T, int = 0>
struct protect_;
template <typename, int = 0>
struct vararg_;
template <typename T, int = 0>
struct is_valid_;
// Returns which branch to evaluate
template <typename If, typename... Ts>
#ifdef META_CONCEPT
using lazy_if_ = lazy::_t<defer<_if_, If, protect_<Ts>...>>;
#else
using lazy_if_ = lazy::_t<defer<_if_, list<If, protect_<Ts>...>>>;
#endif
template <typename A, typename T, typename Fn, typename Ts>
struct subst1_
{
using type = list<list<T>>;
};
template <typename T, typename Fn, typename Ts>
struct subst1_<Fn, T, Fn, Ts>
{
using type = list<>;
};
template <typename A, typename T, typename Fn, typename Ts>
struct subst1_<vararg_<A>, T, Fn, Ts>
{
using type = list<Ts>;
};
template <typename As, typename Ts>
using substitutions_ = push_back<
join<transform<
concat<As, repeat_n_c<size<Ts>{} + 2 - size<As>{}, back<As>>>,
concat<Ts, repeat_n_c<2, back<As>>>,
bind_back<quote_trait<subst1_>, back<As>, drop_c<Ts, size<As>{} - 2>>>>,
list<back<As>>>;
#if 0//def META_CONCEPT
template <list_like As, list_like Ts>
requires (_v<size<Ts>> + 2 >= _v<size<As>>)
using substitutions = substitutions_<As, Ts>;
#else // ^^^ concepts / no concepts vvv
template <typename As, typename Ts>
using substitutions =
#ifdef META_WORKAROUND_MSVC_702792
invoke<if_c<(size<Ts>::value + 2 >= size<As>::value), quote<substitutions_>>, As,
Ts>;
#else // ^^^ workaround ^^^ / vvv no workaround vvv
invoke<if_c<(size<Ts>{} + 2 >= size<As>{}), quote<substitutions_>>, As, Ts>;
#endif // META_WORKAROUND_MSVC_702792
#endif // META_CONCEPT
template <typename T>
struct is_vararg_ : std::false_type
{
};
template <typename T>
struct is_vararg_<vararg_<T>> : std::true_type
{
};
template <META_TYPE_CONSTRAINT(list_like) Tags>
using is_variadic_ = is_vararg_<at<push_front<Tags, void>, dec<size<Tags>>>>;
template <META_TYPE_CONSTRAINT(list_like) Tags, bool IsVariadic = is_variadic_<Tags>::value>
struct lambda_;
// Non-variadic lambda implementation
template <typename... As>
struct lambda_<list<As...>, false>
{
private:
static constexpr std::size_t arity = sizeof...(As) - 1;
using Tags = list<As...>; // Includes the lambda body as the last arg!
using Fn = back<Tags>;
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
struct impl;
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
using lazy_impl_ = lazy::_t<defer<impl, T, protect_<Args>>>;
#if 0//def META_CONCEPT
template <typename, list_like>
#else
template <typename, typename, typename = void>
#endif
struct subst_
{
};
template <template <typename...> class C, typename... Ts, typename Args>
#if 0//def META_CONCEPT
requires valid<C, _t<impl<Ts, Args>>...> struct subst_<defer<C, Ts...>, Args>
#else
struct subst_<defer<C, Ts...>, Args, void_<C<_t<impl<Ts, Args>>...>>>
#endif
{
using type = C<_t<impl<Ts, Args>>...>;
};
template <typename T, template <T...> class C, T... Is, typename Args>
#if 0//def META_CONCEPT
requires valid_i<T, C, Is...> struct subst_<defer_i<T, C, Is...>, Args>
#else
struct subst_<defer_i<T, C, Is...>, Args, void_<C<Is...>>>
#endif
{
using type = C<Is...>;
};
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
struct impl : if_c<(reverse_find_index<Tags, T>() != npos()),
lazy::at<Args, reverse_find_index<Tags, T>>, id<T>>
{
};
template <typename T, typename Args>
struct impl<protect_<T>, Args>
{
using type = T;
};
template <typename T, typename Args>
struct impl<is_valid_<T>, Args>
{
using type = is_trait<impl<T, Args>>;
};
template <typename If, typename... Ts, typename Args>
struct impl<defer<if_, If, Ts...>, Args> // Short-circuit if_
: impl<lazy_impl_<lazy_if_<If, Ts...>, Args>, Args>
{
};
template <typename B, typename... Bs, typename Args>
struct impl<defer<and_, B, Bs...>, Args> // Short-circuit and_
: impl<lazy_impl_<lazy_if_<B, lazy::and_<Bs...>, protect_<std::false_type>>, Args>,
Args>
{
};
template <typename B, typename... Bs, typename Args>
struct impl<defer<or_, B, Bs...>, Args> // Short-circuit or_
: impl<lazy_impl_<lazy_if_<B, protect_<std::true_type>, lazy::or_<Bs...>>, Args>,
Args>
{
};
template <template <typename...> class C, typename... Ts, typename Args>
struct impl<defer<C, Ts...>, Args> : subst_<defer<C, Ts...>, Args>
{
};
template <typename T, template <T...> class C, T... Is, typename Args>
struct impl<defer_i<T, C, Is...>, Args> : subst_<defer_i<T, C, Is...>, Args>
{
};
template <template <typename...> class C, typename... Ts, typename Args>
struct impl<C<Ts...>, Args> : subst_<defer<C, Ts...>, Args>
{
};
template <typename... Ts, typename Args>
struct impl<lambda_<list<Ts...>, false>, Args>
{
using type = compose<uncurry<lambda_<list<As..., Ts...>, false>>,
curry<bind_front<quote<concat>, Args>>>;
};
template <typename... Bs, typename Args>
struct impl<lambda_<list<Bs...>, true>, Args>
{
using type = compose<typename lambda_<list<As..., Bs...>, true>::thunk,
bind_front<quote<concat>, transform<Args, quote<list>>>,
curry<bind_front<quote<substitutions>, list<Bs...>>>>;
};
public:
template <typename... Ts>
#ifdef META_CONCEPT
requires (sizeof...(Ts) == arity) using invoke = _t<impl<Fn, list<Ts..., Fn>>>;
#else
using invoke = _t<if_c<sizeof...(Ts) == arity, impl<Fn, list<Ts..., Fn>>>>;
#endif
};
// Lambda with variadic placeholder (broken out due to less efficient compile-time
// resource usage)
template <typename... As>
struct lambda_<list<As...>, true>
{
private:
template <META_TYPE_CONSTRAINT(list_like) T, bool IsVar>
friend struct lambda_;
using Tags = list<As...>; // Includes the lambda body as the last arg!
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
struct impl;
template <META_TYPE_CONSTRAINT(list_like) Args>
using eval_impl_ = bind_back<quote_trait<impl>, Args>;
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
using lazy_impl_ = lazy::_t<defer<impl, T, protect_<Args>>>;
template <template <typename...> class C, META_TYPE_CONSTRAINT(list_like) Args,
META_TYPE_CONSTRAINT(list_like) Ts>
using try_subst_ = apply<quote<C>, join<transform<Ts, eval_impl_<Args>>>>;
#if 0//def META_CONCEPT
template <typename, list_like>
#else
template <typename, typename, typename = void>
#endif
struct subst_
{
};
template <template <typename...> class C, typename... Ts, typename Args>
#if 0//def META_CONCEPT
requires is_true<try_subst_<C, Args, list<Ts...>>> struct subst_<defer<C, Ts...>, Args>
#else
struct subst_<defer<C, Ts...>, Args, void_<try_subst_<C, Args, list<Ts...>>>>
#endif
{
using type = list<try_subst_<C, Args, list<Ts...>>>;
};
template <typename T, template <T...> class C, T... Is, typename Args>
#if 0//def META_CONCEPT
requires valid_i<T, C, Is...> struct subst_<defer_i<T, C, Is...>, Args>
#else
struct subst_<defer_i<T, C, Is...>, Args, void_<C<Is...>>>
#endif
{
using type = list<C<Is...>>;
};
template <typename T, META_TYPE_CONSTRAINT(list_like) Args>
struct impl : if_c<(reverse_find_index<Tags, T>() != npos()),
lazy::at<Args, reverse_find_index<Tags, T>>, id<list<T>>>
{
};
template <typename T, typename Args>
struct impl<protect_<T>, Args>
{
using type = list<T>;
};
template <typename T, typename Args>
struct impl<is_valid_<T>, Args>
{
using type = list<is_trait<impl<T, Args>>>;
};
template <typename If, typename... Ts, typename Args>
struct impl<defer<if_, If, Ts...>, Args> // Short-circuit if_
: impl<lazy_impl_<lazy_if_<If, Ts...>, Args>, Args>
{
};
template <typename B, typename... Bs, typename Args>
struct impl<defer<and_, B, Bs...>, Args> // Short-circuit and_
: impl<lazy_impl_<lazy_if_<B, lazy::and_<Bs...>, protect_<std::false_type>>, Args>,
Args>
{
};
template <typename B, typename... Bs, typename Args>
struct impl<defer<or_, B, Bs...>, Args> // Short-circuit or_
: impl<lazy_impl_<lazy_if_<B, protect_<std::true_type>, lazy::or_<Bs...>>, Args>,
Args>
{
};
template <template <typename...> class C, typename... Ts, typename Args>
struct impl<defer<C, Ts...>, Args> : subst_<defer<C, Ts...>, Args>
{
};
template <typename T, template <T...> class C, T... Is, typename Args>
struct impl<defer_i<T, C, Is...>, Args> : subst_<defer_i<T, C, Is...>, Args>
{
};
template <template <typename...> class C, typename... Ts, typename Args>
struct impl<C<Ts...>, Args> : subst_<defer<C, Ts...>, Args>
{
};
template <typename... Bs, bool IsVar, typename Args>
struct impl<lambda_<list<Bs...>, IsVar>, Args>
{
using type =
list<compose<typename lambda_<list<As..., Bs...>, true>::thunk,
bind_front<quote<concat>, Args>,
curry<bind_front<quote<substitutions>, list<Bs...>>>>>;
};
struct thunk
{
template <typename S, typename R = _t<impl<back<Tags>, S>>>
#ifdef META_CONCEPT
requires (_v<size<R>> == 1) using invoke = front<R>;
#else
using invoke = if_c<size<R>{} == 1, front<R>>;
#endif
};
public:
template <typename... Ts>
using invoke = invoke<thunk, substitutions<Tags, list<Ts...>>>;
};
} // namespace detail
/// \endcond
///////////////////////////////////////////////////////////////////////////////////////////
// lambda
/// For creating anonymous Invocables.
/// \code
/// using L = lambda<_a, _b, std::pair<_b, std::pair<_a, _a>>>;
/// using P = invoke<L, int, short>;
/// static_assert(std::is_same_v<P, std::pair<short, std::pair<int, int>>>, "");
/// \endcode
/// \ingroup trait
template <typename... Ts>
#ifdef META_CONCEPT
requires (sizeof...(Ts) > 0) using lambda = detail::lambda_<list<Ts...>>;
#else
using lambda = if_c<(sizeof...(Ts) > 0), detail::lambda_<list<Ts...>>>;
#endif
///////////////////////////////////////////////////////////////////////////////////////////
// is_valid
/// For testing whether a deferred computation will succeed in a \c let or a \c lambda.
/// \ingroup trait
template <typename T>
using is_valid = detail::is_valid_<T>;
///////////////////////////////////////////////////////////////////////////////////////////
// vararg
/// For defining variadic placeholders.
template <typename T>
using vararg = detail::vararg_<T>;
///////////////////////////////////////////////////////////////////////////////////////////
// protect
/// For preventing the evaluation of a nested `defer`ed computation in a \c let or
/// \c lambda expression.
template <typename T>
using protect = detail::protect_<T>;
///////////////////////////////////////////////////////////////////////////////////////////
// var
/// For use when defining local variables in \c meta::let expressions
/// \sa `meta::let`
template <typename Tag, typename Value>
struct var;
/// \cond
namespace detail
{
template <typename...>
struct let_
{
};
template <typename Fn>
struct let_<Fn>
{
using type = lazy::invoke<lambda<Fn>>;
};
template <typename Tag, typename Value, typename... Rest>
struct let_<var<Tag, Value>, Rest...>
{
using type = lazy::invoke<lambda<Tag, _t<let_<Rest...>>>, Value>;
};
} // namespace detail
/// \endcond
/// A lexically scoped expression with local variables.
///
/// \code
/// template <typename T, typename L>
/// using find_index_ = let<
/// var<_a, L>,
/// var<_b, lazy::find<_a, T>>,
/// lazy::if_<
/// std::is_same<_b, list<>>,
/// meta::npos,
/// lazy::minus<lazy::size<_a>, lazy::size<_b>>>>;
/// static_assert(find_index_<int, list<short, int, float>>{} == 1, "");
/// static_assert(find_index_<double, list<short, int, float>>{} == meta::npos{}, "");
/// \endcode
/// \ingroup trait
template <typename... As>
using let = _t<_t<detail::let_<As...>>>;
namespace lazy
{
/// \sa `meta::let`
/// \ingroup lazy_trait
template <typename... As>
using let = defer<let, As...>;
} // namespace lazy
// Some argument placeholders for use in \c lambda expressions.
/// \ingroup trait
inline namespace placeholders
{
// regular placeholders:
struct _a;
struct _b;
struct _c;
struct _d;
struct _e;
struct _f;
struct _g;
struct _h;
struct _i;
// variadic placeholders:
using _args = vararg<void>;
using _args_a = vararg<_a>;
using _args_b = vararg<_b>;
using _args_c = vararg<_c>;
} // namespace placeholders
///////////////////////////////////////////////////////////////////////////////////////////
// cartesian_product
/// \cond
namespace detail
{
template <typename M2, typename M>
struct cartesian_product_fn
{
template <typename X>
struct lambda0
{
template <typename Xs>
using lambda1 = list<push_front<Xs, X>>;
using type = join<transform<M2, quote<lambda1>>>;
};
using type = join<transform<M, quote_trait<lambda0>>>;
};
} // namespace detail
/// \endcond
/// Given a list of lists \p ListOfLists, return a new list of lists that is the Cartesian
/// Product. Like the `sequence` function from the Haskell Prelude.
/// \par Complexity
/// \f$ O(N \times M) \f$, where \f$ N \f$ is the size of the outer list, and
/// \f$ M \f$ is the size of the inner lists.
/// \ingroup transformation
template <META_TYPE_CONSTRAINT(list_like) ListOfLists>
using cartesian_product =
reverse_fold<ListOfLists, list<list<>>, quote_trait<detail::cartesian_product_fn>>;
namespace lazy
{
/// \sa 'meta::cartesian_product'
/// \ingroup lazy_transformation
template <typename ListOfLists>
using cartesian_product = defer<cartesian_product, ListOfLists>;
} // namespace lazy
/// \cond
///////////////////////////////////////////////////////////////////////////////////////////
// add_const_if
namespace detail
{
template <bool>
struct add_const_if
{
template <typename T>
using invoke = T const;
};
template <>
struct add_const_if<false>
{
template <typename T>
using invoke = T;
};
} // namespace detail
template <bool If>
using add_const_if_c = detail::add_const_if<If>;
template <META_TYPE_CONSTRAINT(integral) If>
using add_const_if = add_const_if_c<If::type::value>;
/// \endcond
/// \cond
///////////////////////////////////////////////////////////////////////////////////////////
// const_if
template <bool If, typename T>
using const_if_c = typename add_const_if_c<If>::template invoke<T>;
template <typename If, typename T>