25 Algorithms library [algorithms]

25.10 Generalized numeric operations [numeric.ops]

25.10.6 Transform reduce [transform.reduce]

template<class InputIterator1, class InputIterator2, class T>
  constexpr T transform_reduce(InputIterator1 first1, InputIterator1 last1,
                               InputIterator2 first2,
                               T init);

Effects: Equivalent to: return transform_reduce(first1, last1, first2, init, plus<>(), multiplies<>());

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template<class ExecutionPolicy,
         class ForwardIterator1, class ForwardIterator2, class T>
  T transform_reduce(ExecutionPolicy&& exec,
                     ForwardIterator1 first1, ForwardIterator1 last1,
                     ForwardIterator2 first2,
                     T init);

Effects: Equivalent to: return transform_reduce(std::forward<ExecutionPolicy>(exec), first1, last1, first2, init, plus<>(), multiplies<>());

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template<class InputIterator1, class InputIterator2, class T,
         class BinaryOperation1, class BinaryOperation2>
  constexpr T transform_reduce(InputIterator1 first1, InputIterator1 last1,
                               InputIterator2 first2,
                               T init,
                               BinaryOperation1 binary_op1,
                               BinaryOperation2 binary_op2);
template<class ExecutionPolicy,
         class ForwardIterator1, class ForwardIterator2, class T,
         class BinaryOperation1, class BinaryOperation2>
  T transform_reduce(ExecutionPolicy&& exec,
                     ForwardIterator1 first1, ForwardIterator1 last1,
                     ForwardIterator2 first2,
                     T init,
                     BinaryOperation1 binary_op1,
                     BinaryOperation2 binary_op2);

Mandates: All of

(3.1)
binary_op1(init, init),
(3.2)
binary_op1(init, binary_op2(*first1, *first2)),
(3.3)
binary_op1(binary_op2(*first1, *first2), init), and
(3.4)
binary_op1(binary_op2(*first1, *first2), binary_op2(*first1, *first2))

are convertible to T.

Preconditions:

(4.1)
T meets the Cpp17MoveConstructible (Table 28) requirements.
(4.2)
Neither binary_op1 nor binary_op2 invalidates subranges, nor modifies elements in the ranges [first1, last1] and [first2, first2 + (last1 - first1)].

Returns: GENERALIZED_SUM(binary_op1, init, binary_op2(*i, *(first2 + (i - first1))), ...) for every iterator i in [first1, last1).

Complexity:

O (last1 - first1)

applications each of binary_op1 and binary_op2.

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template<class InputIterator, class T,
         class BinaryOperation, class UnaryOperation>
  constexpr T transform_reduce(InputIterator first, InputIterator last, T init,
                               BinaryOperation binary_op, UnaryOperation unary_op);
template<class ExecutionPolicy,
         class ForwardIterator, class T,
         class BinaryOperation, class UnaryOperation>
  T transform_reduce(ExecutionPolicy&& exec,
                     ForwardIterator first, ForwardIterator last,
                     T init, BinaryOperation binary_op, UnaryOperation unary_op);

Mandates: All of

(7.1)
binary_op(init, init),
(7.2)
binary_op(init, unary_op(*first)),
(7.3)
binary_op(unary_op(*first), init), and
(7.4)
binary_op(unary_op(*first), unary_op(*first))

are convertible to T.

Preconditions:

(8.1)
T meets the Cpp17MoveConstructible (Table 28) requirements.
(8.2)
Neither unary_op nor binary_op invalidates subranges, nor modifies elements in the range [first, last].

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

Complexity:

O (last - first)

applications each of unary_op and binary_op.

[Note 1:

transform_reduce does not apply unary_op to init.

— end note]