std::transform

 

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算法库

功能 Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
修改序列操作 Original: Non-modifying sequence operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
all_of any_of none_of （C++11） （C++11） （C++11） for_each count count_if mismatch equal	find find_if find_if_not （C++11） find_end find_first_of adjacent_find search search_n
修改序列操作 Original: Modifying sequence operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
copy copy_if （C++11） copy_n （C++11） copy_backward move （C++11） move_backward （C++11） fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   （C++11） unique unique_copy
分区操作 Original: Partitioning operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_partitioned （C++11） partition partition_copy （C++11）	stable_partition partition_point （C++11）
排序操作（排序的区间） Original: Sorting operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_sorted （C++11） is_sorted_until （C++11） sort	partial_sort partial_sort_copy stable_sort nth_element
二进制搜索操作（排序的区间） Original: Binary search operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
lower_bound upper_bound	binary_search equal_range
设置操作（排序的区间） Original: Set operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
堆的操作 Original: Heap operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_heap is_heap_until （C++11） make_heap	push_heap pop_heap sort_heap
最小/最大操作 Original: Minimum/maximum operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
max max_element min min_element minmax （C++11） minmax_element （C++11）	lexicographical_compare is_permutation （C++11） next_permutation prev_permutation
数字操作 Original: Numeric operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
iota （C++11） accumulate inner_product	adjacent_difference partial_sum
C库 Original: C library The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
qsort	bsearch

 

Defined in header <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施加给定的功能的范围内，并存储在另一个范围内的结果，开始在d_first.

Original:

std::transform applies the given function to a range and stores the result in another range, beginning at d_first.

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在第一个版本的一元运算unary_op被施加到限定的范围内由[first1, last1)。在第二个版本的二进制运算binary_op元素对被施加到从两个范围：1定义的和其他的开始[first1, last1)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.

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参数

first1, last1	-	第一个范围的元素进行改造 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	-	变换的元素的第二范围的开头 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	-	目标范围的开始，可以等于first1或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.

返回值

输出迭代器改变了过去的最后一个元素的元素.

Original:

output iterator to the element past the last element transformed.

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复杂性

1)

究竟std::distance(first1, last1)应用unary_op

Original:

exactly std::distance(first1, last1) applications of unary_op

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2)

究竟std::distance(first1, last1)应用binary_op

Original:

exactly std::distance(first1, last1) applications of binary_op

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要求

unary_op和binary_op没有任何副作用。 （至 C++11）

Original:

unary_op and binary_op have no side effects. （至 C++11）

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unary_opbinary_op没有任何迭代器失效，其中包括结束迭代器，或修改任何元素所涉及的范围。 （C++11 起）

Original:

unary_op and binary_op do not invalidate any iterators, including the end iterators, or modify any elements of the ranges involved. （C++11 起）

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这些规定的目的是让平行或序std::transform实现。应用功能有序的序列，使用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.

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可能的实现

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; }

为例

下面的代码使用转换将字符串转换为大写toupper函数的使用

Original:

The following code uses transform to convert a string to uppercase using the toupper function:

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#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;
 }

Output:

HELLO

另请参阅

for_each	某一范围的元素应用一个函数 Original: applies a function to a range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）