Fix compiler warnings

src/compat/glibcxx_sanity.cpp

@@ -47,7 +47,7 @@ bool sanity_test_range_fmt()
 {
     std::string test;
     try {
-        test.at(1);
+        (void) test.at(1);
     } catch (const std::out_of_range&) {
         return true;
     } catch (...) {

src/immer/algorithm.hpp

@@ -9,6 +9,8 @@
 #pragma once
 
 #include <algorithm>
+#include <cassert>
+#include <functional>
 #include <numeric>
 #include <type_traits>
 
@@ -47,8 +49,8 @@ template <typename Iterator, typename Fn>
 void for_each_chunk(const Iterator& first, const Iterator& last, Fn&& fn)
 {
     assert(&first.impl() == &last.impl());
-    first.impl().for_each_chunk(first.index(), last.index(),
-                                std::forward<Fn>(fn));
+    first.impl().for_each_chunk(
+        first.index(), last.index(), std::forward<Fn>(fn));
 }
 
 template <typename T, typename Fn>
@@ -81,8 +83,8 @@ template <typename Iterator, typename Fn>
 bool for_each_chunk_p(const Iterator& first, const Iterator& last, Fn&& fn)
 {
     assert(&first.impl() == &last.impl());
-    return first.impl().for_each_chunk_p(first.index(), last.index(),
-                                         std::forward<Fn>(fn));
+    return first.impl().for_each_chunk_p(
+        first.index(), last.index(), std::forward<Fn>(fn));
 }
 
 template <typename T, typename Fn>
@@ -91,23 +93,43 @@ bool for_each_chunk_p(const T* first, const T* last, Fn&& fn)
     return std::forward<Fn>(fn)(first, last);
 }
 
+namespace detail {
+
+template <class Iter, class T>
+T accumulate_move(Iter first, Iter last, T init)
+{
+    for (; first != last; ++first)
+        init = std::move(init) + *first;
+    return init;
+}
+
+template <class Iter, class T, class Fn>
+T accumulate_move(Iter first, Iter last, T init, Fn op)
+{
+    for (; first != last; ++first)
+        init = op(std::move(init), *first);
+    return init;
+}
+
+} // namespace detail
+
 /*!
  * Equivalent of `std::accumulate` applied to the range `r`.
  */
 template <typename Range, typename T>
 T accumulate(Range&& r, T init)
 {
-    for_each_chunk(r, [&] (auto first, auto last) {
-        init = std::accumulate(first, last, init);
+    for_each_chunk(r, [&](auto first, auto last) {
+        init = detail::accumulate_move(first, last, init);
     });
     return init;
 }
 
 template <typename Range, typename T, typename Fn>
 T accumulate(Range&& r, T init, Fn fn)
 {
-    for_each_chunk(r, [&] (auto first, auto last) {
-        init = std::accumulate(first, last, init, fn);
+    for_each_chunk(r, [&](auto first, auto last) {
+        init = detail::accumulate_move(first, last, init, fn);
     });
     return init;
 }
@@ -119,17 +141,17 @@ T accumulate(Range&& r, T init, Fn fn)
 template <typename Iterator, typename T>
 T accumulate(Iterator first, Iterator last, T init)
 {
-    for_each_chunk(first, last, [&] (auto first, auto last) {
-        init = std::accumulate(first, last, init);
+    for_each_chunk(first, last, [&](auto first, auto last) {
+        init = detail::accumulate_move(first, last, init);
     });
     return init;
 }
 
 template <typename Iterator, typename T, typename Fn>
 T accumulate(Iterator first, Iterator last, T init, Fn fn)
 {
-    for_each_chunk(first, last, [&] (auto first, auto last) {
-        init = std::accumulate(first, last, init, fn);
+    for_each_chunk(first, last, [&](auto first, auto last) {
+        init = detail::accumulate_move(first, last, init, fn);
     });
     return init;
 }
@@ -140,7 +162,7 @@ T accumulate(Iterator first, Iterator last, T init, Fn fn)
 template <typename Range, typename Fn>
 Fn&& for_each(Range&& r, Fn&& fn)
 {
-    for_each_chunk(r, [&] (auto first, auto last) {
+    for_each_chunk(r, [&](auto first, auto last) {
         for (; first != last; ++first)
             fn(*first);
     });
@@ -154,7 +176,7 @@ Fn&& for_each(Range&& r, Fn&& fn)
 template <typename Iterator, typename Fn>
 Fn&& for_each(Iterator first, Iterator last, Fn&& fn)
 {
-    for_each_chunk(first, last, [&] (auto first, auto last) {
+    for_each_chunk(first, last, [&](auto first, auto last) {
         for (; first != last; ++first)
             fn(*first);
     });
@@ -167,9 +189,8 @@ Fn&& for_each(Iterator first, Iterator last, Fn&& fn)
 template <typename Range, typename OutIter>
 OutIter copy(Range&& r, OutIter out)
 {
-    for_each_chunk(r, [&] (auto first, auto last) {
-        out = std::copy(first, last, out);
-    });
+    for_each_chunk(
+        r, [&](auto first, auto last) { out = std::copy(first, last, out); });
     return out;
 }
 
@@ -180,7 +201,7 @@ OutIter copy(Range&& r, OutIter out)
 template <typename InIter, typename OutIter>
 OutIter copy(InIter first, InIter last, OutIter out)
 {
-    for_each_chunk(first, last, [&] (auto first, auto last) {
+    for_each_chunk(first, last, [&](auto first, auto last) {
         out = std::copy(first, last, out);
     });
     return out;
@@ -192,9 +213,8 @@ OutIter copy(InIter first, InIter last, OutIter out)
 template <typename Range, typename Pred>
 bool all_of(Range&& r, Pred p)
 {
-    return for_each_chunk_p(r, [&] (auto first, auto last) {
-        return std::all_of(first, last, p);
-    });
+    return for_each_chunk_p(
+        r, [&](auto first, auto last) { return std::all_of(first, last, p); });
 }
 
 /*!
@@ -204,11 +224,102 @@ bool all_of(Range&& r, Pred p)
 template <typename Iter, typename Pred>
 bool all_of(Iter first, Iter last, Pred p)
 {
-    return for_each_chunk_p(first, last, [&] (auto first, auto last) {
+    return for_each_chunk_p(first, last, [&](auto first, auto last) {
         return std::all_of(first, last, p);
     });
 }
 
+/*!
+ * Object that can be used to process changes as computed by the @a diff
+ * algorithm.
+ *
+ * @tparam AddedFn Unary function that is be called whenever an added element is
+ *         found. It is called with the added element as argument.
+ *
+ * @tparam RemovedFn Unary function that is called whenever a removed element is
+ *         found.  It is called with the removed element as argument.
+ *
+ * @tparam ChangedFn Unary function that is called whenever a changed element is
+ *         found.  It is called with the changed element as argument.
+ */
+template <class AddedFn, class RemovedFn, class ChangedFn>
+struct differ
+{
+    AddedFn added;
+    RemovedFn removed;
+    ChangedFn changed;
+};
+
+/*!
+ * Produces a @a differ object with `added`, `removed` and `changed` functions.
+ */
+template <class AddedFn, class RemovedFn, class ChangedFn>
+auto make_differ(AddedFn&& added, RemovedFn&& removed, ChangedFn&& changed)
+    -> differ<std::decay_t<AddedFn>,
+              std::decay_t<RemovedFn>,
+              std::decay_t<ChangedFn>>
+{
+    return {std::forward<AddedFn>(added),
+            std::forward<RemovedFn>(removed),
+            std::forward<ChangedFn>(changed)};
+}
+
+/*!
+ * Produces a @a differ object with `added` and `removed` functions and no
+ * `changed` function.
+ */
+template <class AddedFn, class RemovedFn>
+auto make_differ(AddedFn&& added, RemovedFn&& removed)
+{
+    return make_differ(std::forward<AddedFn>(added),
+                       std::forward<RemovedFn>(removed),
+                       [](auto&&...) {});
+}
+
+/*!
+ * Compute the differences between `a` and `b`.
+ *
+ * Changes detected are notified via the differ object, which should support the
+ * following expressions:
+ *
+ *   - `differ.added(x)`, invoked when element `x` is found in `b` but not in
+ *      `a`.
+ *
+ *   - `differ.removed(x)`, invoked when element `x` is found in `a` but not in
+ *      `b`.
+ *
+ *   - `differ.changed(x, y)`, invoked when element `x` and `y` from `a` and `b`
+ *      share the same key but map to a different value.
+ *
+ * This method leverages structural sharing to offer a complexity @f$ O(|diff|)
+ * @f$ when `b` is derived from `a` by performing @f$ |diff| @f$ updates.  This
+ * is, this function can detect changes in effectively constant time per update,
+ * as oposed to the @f$ O(|a|+|b|) @f$ complexity of a trivial implementation.
+ *
+ * @rst
+ *
+ * .. note:: This method is only implemented for ``map`` and ``set``. When sets
+ *           are diffed, the ``changed`` function is never called.
+ *
+ * @endrst
+ */
+template <typename T, typename Differ>
+void diff(const T& a, const T& b, Differ&& differ)
+{
+    a.impl().template diff<std::equal_to<typename T::value_type>>(
+        b.impl(), std::forward<Differ>(differ));
+}
+
+/*!
+ * Compute the differences between `a` and `b` using the callbacks in `fns` as
+ * differ.  Equivalent to `diff(a, b, make_differ(fns)...)`.
+ */
+template <typename T, typename... Fns>
+void diff(const T& a, const T& b, Fns&&... fns)
+{
+    diff(a, b, make_differ(std::forward<Fns>(fns)...));
+}
+
 /** @} */ // group: algorithm
 
 } // namespace immer