26 Numerics library [numerics]

26.8 Generalized numeric operations [numeric.ops]

26.8.3 Reduce [reduce]

template<class InputIterator> typename iterator_traits<InputIterator>::value_type reduce(InputIterator first, InputIterator last);

1

Effects: Equivalent to: 

return reduce(first, last,
              typename iterator_traits<InputIterator>::value_type{});

template<class ExecutionPolicy, class InputIterator> typename iterator_traits<InputIterator>::value_type reduce(ExecutionPolicy&& exec, InputIterator first, InputIterator last);

2

Effects: Equivalent to: 

return reduce(std::forward<ExecutionPolicy>(exec), first, last,
              typename iterator_traits<InputIterator>::value_type{});

template<class InputIterator, class T> T reduce(InputIterator first, InputIterator last, T init);

3

Effects: Equivalent to: 

return reduce(first, last, init, plus<>());

template<class ExecutionPolicy, class InputIterator, class T> T reduce(ExecutionPolicy&& exec, InputIterator first, InputIterator last, T init);

4

Effects: Equivalent to: 

return reduce(std::forward<ExecutionPolicy>(exec), first, last, init, plus<>());

template<class InputIterator, class T, class BinaryOperation> T reduce(InputIterator first, InputIterator last, T init, BinaryOperation binary_op); template<class ExecutionPolicy, class InputIterator, class T, class BinaryOperation> T reduce(ExecutionPolicy&& exec, InputIterator first, InputIterator last, T init, BinaryOperation binary_op);

5

Requires: binary_op shall neither invalidate iterators or subranges, nor modify elements in the range [first, last).

6

Returns: GENERALIZED_SUM(binary_op, init, *i, ...) for every i in [first, last).

7

Complexity: Ο(last - first) applications of binary_op.

8

Notes: The difference between reduce and accumulate is that reduce applies binary_op in an unspecified order, which yields a nondeterministic result for non-associative or non-commutative binary_op such as floating-point addition.