fold

Header pipe/algorithm.h, in namespace pipe::algorithm.

template <typename BinaryOperation>
auto fold(BinaryOperation op);

fold returns an object which can act as a rhs when applying operator| to a lhs generator. When applied, it combines all elements yielded by the input generator using the given BinaryOperation, returns the generator's value type default value if no elements are generated.

Example:

auto out = count() | take_n(5) | fold(std::plus<> {});
// out contains 10 (0 + 1 + 2 + 3 + 4)