Пространства имён
Варианты
Действия

std::transform

Материал из cppreference.com

This page has been machine-translated from the English version of the wiki using Google Translate.

The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

 
C++
 
Алгоритмы
Функции
Немодифицирующие линейные операции
Модифицирующие линейные операции
Разделение
Сортировка (на отсортированных промежутках)
Бинарный поиск (на отсортированных промежутках)
Множества (на отсортированных промежутках)
Куча
Минимум/максимум
Числовые операции
Библиотека C
 
Заголовочный файл <algorithm>
template< class InputIt, class OutputIt, class UnaryOperation >

OutputIt transform( InputIt first1, InputIt last1, OutputIt d_first,

                    UnaryOperation unary_op );
 (1)
template< class InputIt1, class InputIt2, class OutputIt, class BinaryOperation >

OutputIt transform( InputIt1 first1, InputIt1 last1, InputIt2 first2,

                    OutputIt d_first, BinaryOperation binary_op );
 (2)
std::transform применяется данная функция диапазона и сохраняет результат в другом диапазоне, начиная с d_first.
Original:
std::transform applies the given function to a range and stores the result in another range, beginning at d_first.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
В первой версии унарный unary_op операция применяется к диапазон, определенный [first1, last1). Во второй версии двоичного binary_op операция применяется к парам элементов из двух диапазонов: один определяется [first1, last1) и другие Начало в first2.
Original:
In the first version unary operation unary_op is applied to the range defined by [first1, last1). In the second version the binary operation binary_op is applied to pairs of elements from two ranges: one defined by [first1, last1) and the other beginning at first2.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Содержание

[править] Параметры

first1, last1 -
первый ряд элементов для преобразования
Original:
the first range of elements to transform
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
first2 -
В начале второго диапазона элементов для преобразования
Original:
the beginning of the second range of elements to transform
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
d_first -
В начале назначения диапазона, может быть равным или first1 first2
Original:
the beginning of the destination range, may be equal to first1 or first2
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unary_op - unary operation function object that will be applied.

The signature of the function should be equivalent to the following:

Ret fun(const Type &a);

The signature does not need to have const &.
The type  Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to  Type. The type  Ret must be such that an object of type OutputIt can be dereferenced and assigned a value of type  Ret. ​

binary_op - binary operation function object that will be applied.

The signature of the function should be equivalent to the following:

Ret fun(const Type1 &a, const Type2 &b);

The signature does not need to have const &.
The types  Type1 and  Type2 must be such that objects of types InputIt1 and InputIt2 can be dereferenced and then implicitly converted to  Type1 and  Type2 respectively. The type  Ret must be such that an object of type OutputIt can be dereferenced and assigned a value of type  Ret. ​

Type requirements
-
InputIt must meet the requirements of InputIterator.
-
InputIt1 must meet the requirements of InputIterator.
-
InputIt2 must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[править] Возвращаемое значение

выходной итератор на элемент после последнего элемента превращаются.
Original:
output iterator to the element past the last element transformed.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[править] Сложность

1)
точно std::distance(first1, last1) применения unary_op
Original:
exactly std::distance(first1, last1) applications of unary_op
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
2)
точно std::distance(first1, last1) применения binary_op
Original:
exactly std::distance(first1, last1) applications of binary_op
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[править] Требования

unary_op и binary_op не имеют побочных эффектов. (до C++11)
Original:
unary_op and binary_op have no side effects. (до C++11)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unary_op и binary_op не аннулированию итераторов, в том числе в конце итераторы, или изменять любые элементы диапазонов участие. (начиная с C++11)
Original:
unary_op and binary_op do not invalidate any iterators, including the end iterators, or modify any elements of the ranges involved. (начиная с C++11)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Целью этих требований является возможность параллельного или вне порядка реализации std::transform. Чтобы применить функцию к последовательности в порядке, используйте std::for_each.
Original:
The intent of these requirements is to allow parallel or out-of-order implementations of std::transform. To apply a function to a sequence in-order, use std::for_each.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[править] Возможная реализация

First version 
template<class InputIt, class OutputIt, class UnaryOperation>
OutputIt transform(InputIt first1, InputIt last1, OutputIt d_first,
                   UnaryOperation unary_op)
{
    while (first1 != last1) {
        *d_first++ = unary_op(*first1++);
    }
    return d_first;
}
Second version 
template<class InputIt1, class InputIt2,
         class OutputIt, class BinaryOperation>
OutputIt transform(InputIt first1, InputIt last1, InputIt first2,
                   OutputIt d_first, BinaryOperation binary_op)
{
    while (first1 != last1) {
        *d_first++ = binary_op(*first1++, *first2++);
    }
    return d_first;
}

[править] Пример

Следующий код использует преобразования для преобразования строки в верхний регистр помощью ToUpper функции:
Original:
The following code uses transform to convert a string to uppercase using the toupper function:
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <string>
#include <cctype>
#include <algorithm>
#include <iostream>
 
int main()
{
    std::string s("hello");
    std::transform(s.begin(), s.end(), s.begin(), (int (*)(int))std::toupper);
    std::cout << s;
 }

Вывод: 

HELLO

[править] См. также

{{dcl list tfun | cpp/algorithm/for_each |применяет функцию к диапазону элементов
Источник — «http://ru.cppreference.com/mwiki/index.php?title=cpp/algorithm/transform&oldid=30553»