From Jason Turner

[transform.inclusive.scan]

C++17 → C++20 4.2 KB 52 lines
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  ### Transform inclusive scan <a id="transform.inclusive.scan">[[transform.inclusive.scan]]</a>
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  ``` cpp
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  template<class InputIterator, class OutputIterator,
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  class BinaryOperation, class UnaryOperation>
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- OutputIterator transform_inclusive_scan(InputIterator first, InputIterator last,
 
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  OutputIterator result,
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- BinaryOperation binary_op,
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- UnaryOperation unary_op);
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  template<class ExecutionPolicy,
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  class ForwardIterator1, class ForwardIterator2,
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  class BinaryOperation, class UnaryOperation>
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- ForwardIterator2 transform_inclusive_scan(ExecutionPolicy&& exec,
 
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  ForwardIterator1 first, ForwardIterator1 last,
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  ForwardIterator2 result,
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- BinaryOperation binary_op,
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- UnaryOperation unary_op);
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  template<class InputIterator, class OutputIterator,
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  class BinaryOperation, class UnaryOperation, class T>
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- OutputIterator transform_inclusive_scan(InputIterator first, InputIterator last,
 
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  OutputIterator result,
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- BinaryOperation binary_op,
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- UnaryOperation unary_op,
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  T init);
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  template<class ExecutionPolicy,
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  class ForwardIterator1, class ForwardIterator2,
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  class BinaryOperation, class UnaryOperation, class T>
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- ForwardIterator2 transform_inclusive_scan(ExecutionPolicy&& exec,
 
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  ForwardIterator1 first, ForwardIterator1 last,
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  ForwardIterator2 result,
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- BinaryOperation binary_op,
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- UnaryOperation unary_op,
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  T init);
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  ```
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- *Requires:*
 
 
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- - If `init` is provided, `T` shall be `MoveConstructible`
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- (Table  [[tab:moveconstructible]]); otherwise, `ForwardIterator1`’s
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- value type shall be `MoveConstructible`.
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- - If `init` is provided, all of
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  - `binary_op(init, init)`,
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  - `binary_op(init, unary_op(*first))`, and
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  - `binary_op(unary_op(*first), unary_op(*first))`
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- shall be convertible to `T`; otherwise,
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- `binary_op(unary_op(*first), unary_op(*first))` shall be convertible
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- to `ForwardIterator1`’s value type.
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- - Neither `unary_op` nor `binary_op` shall invalidate iterators or
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- subranges, nor modify elements in the ranges \[`first`, `last`\] or
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- \[`result`, `result + (last - first)`\].
 
 
 
 
 
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  *Effects:* For each integer `K` in \[`0`, `last - first`) assigns
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  through `result + K` the value of
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  - *GENERALIZED_NONCOMMUTATIVE_SUM*(
 
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  ### Transform inclusive scan <a id="transform.inclusive.scan">[[transform.inclusive.scan]]</a>
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  ``` cpp
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  template<class InputIterator, class OutputIterator,
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  class BinaryOperation, class UnaryOperation>
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+ constexpr OutputIterator
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+ transform_inclusive_scan(InputIterator first, InputIterator last,
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  OutputIterator result,
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+ BinaryOperation binary_op, UnaryOperation unary_op);
 
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  template<class ExecutionPolicy,
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  class ForwardIterator1, class ForwardIterator2,
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  class BinaryOperation, class UnaryOperation>
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+ ForwardIterator2
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+ transform_inclusive_scan(ExecutionPolicy&& exec,
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  ForwardIterator1 first, ForwardIterator1 last,
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  ForwardIterator2 result,
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+ BinaryOperation binary_op, UnaryOperation unary_op);
 
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  template<class InputIterator, class OutputIterator,
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  class BinaryOperation, class UnaryOperation, class T>
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+ constexpr OutputIterator
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+ transform_inclusive_scan(InputIterator first, InputIterator last,
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  OutputIterator result,
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+ BinaryOperation binary_op, UnaryOperation unary_op,
 
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  T init);
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  template<class ExecutionPolicy,
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  class ForwardIterator1, class ForwardIterator2,
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  class BinaryOperation, class UnaryOperation, class T>
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+ ForwardIterator2
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+ transform_inclusive_scan(ExecutionPolicy&& exec,
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  ForwardIterator1 first, ForwardIterator1 last,
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  ForwardIterator2 result,
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+ BinaryOperation binary_op, UnaryOperation unary_op,
 
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  T init);
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  ```
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+ Let `U` be the value type of `decltype(first)`.
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+
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+ *Mandates:* If `init` is provided, all of
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  - `binary_op(init, init)`,
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  - `binary_op(init, unary_op(*first))`, and
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  - `binary_op(unary_op(*first), unary_op(*first))`
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+ are convertible to `T`; otherwise,
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+ `binary_op(unary_op(*first), unary_op(*first))` is convertible to `U`.
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+
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+ *Preconditions:*
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+
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+ - If `init` is provided, `T` meets the *Cpp17MoveConstructible*
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+ ([[cpp17.moveconstructible]]) requirements; otherwise, `U` meets the
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+ *Cpp17MoveConstructible* requirements.
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+ - Neither `unary_op` nor `binary_op` invalidates iterators or subranges,
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+ nor modifies elements in the ranges \[`first`, `last`\] or \[`result`,
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+ `result + (last - first)`\].
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  *Effects:* For each integer `K` in \[`0`, `last - first`) assigns
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  through `result + K` the value of
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  - *GENERALIZED_NONCOMMUTATIVE_SUM*(