std::transform
Defined in header <algorithm>
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template< class InputIt, class OutputIt, class UnaryOperation > OutputIt transform( InputIt first1, InputIt last1, OutputIt d_first, |
(1) | |
template< class InputIt1, class InputIt2, class OutputIt, class BinaryOperation > OutputIt transform( InputIt1 first1, InputIt1 last1, InputIt2 first2, |
(2) | |
std::transform
applies the given function to a range and stores the result in another range, beginning at d_first
.
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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(until C++11) |
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(since C++11) |
Contents |
[edit] Parameters
first1, last1 | - | the first range of elements to transform |
first2 | - | the beginning of the second range of elements to transform |
d_first | - | the beginning of the destination range, may be equal to first1 or first2
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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 &. |
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 &. |
Type requirements | ||
-InputIt must meet the requirements of InputIterator .
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-InputIt1 must meet the requirements of InputIterator .
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-InputIt2 must meet the requirements of InputIterator .
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-OutputIt must meet the requirements of OutputIterator .
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[edit] Return value
Output iterator to the element past the last element transformed.
[edit] Complexity
[edit] Possible implementation
First version |
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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(InputIt1 first1, InputIt1 last1, InputIt2 first2, OutputIt d_first, BinaryOperation binary_op) { while (first1 != last1) { *d_first++ = binary_op(*first1++, *first2++); } return d_first; } |
[edit] Notes
std::transform
does not guarantee in-order application of unary_op
or binary_op
. To apply a function to a sequence in-order or to apply a function that modifies the elements of a sequence, use std::for_each
[edit] Example
The following code uses transform to convert a string to uppercase using the toupper function:
#include <string> #include <ctype.h> #include <algorithm> #include <functional> #include <iostream> int main() { std::string s("hello"); std::transform(s.begin(), s.end(), s.begin(), ::toupper); std::cout << s; }
Output:
HELLO
[edit] See also
applies a function to a range of elements (function template) | |
(parallelism TS) |
parallelized version of std::transform (function template) |