# 27 Algorithms library [algorithms]

## 27.10 Generalized numeric operations [numeric.ops]

### 27.10.6 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<>());
```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<>());
```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
• binary_op1(init, init),
• binary_op1(init, binary_op2(*first1, *first2)),
• binary_op1(binary_op2(*first1, *first2), init), and
• binary_op1(binary_op2(*first1, *first2), binary_op2(*first1, *first2))
are convertible to T.
Preconditions:
• T meets the Cpp17MoveConstructible (Table 31) requirements.
• 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: applications each of binary_op1 and binary_op2.
```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
• binary_op(init, init),
• binary_op(init, unary_op(*first)),
• binary_op(unary_op(*first), init), and
• binary_op(unary_op(*first), unary_op(*first))
are convertible to T.
Preconditions:
Returns: GENERALIZED_SUM(binary_op, init, unary_op(*i), ...) for every iterator i in [first, last).
Complexity: applications each of unary_op and binary_op.
[Note 1:
transform_reduce does not apply unary_op to init.
â€” end note]