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std::transform

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C++
 
Algorithm Bibliothek
Funktionen
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Functions
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Nicht-modifizierende Sequenz Operationen
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Non-modifying sequence operations
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Modifizierende Sequenz Operationen
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Modifying sequence operations
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Partitionierungsoperationen
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Partitioning operations
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Sortierung Operationen (auf sortierten Bereiche)
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Sorting operations (on sorted ranges)
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Binary Suchaktionen (auf sortierten Bereiche)
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Binary search operations (on sorted ranges)
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Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap-Operationen
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Heap operations
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Minimum / Maximum Operationen
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Minimum/maximum operations
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Numerische Operationen
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Numeric operations
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C-Bibliothek
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C library
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definiert 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 gilt die angegebene Funktion auf einer Reihe und speichert das Ergebnis in einem anderen Bereich, beginnend bei 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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In der ersten Version unäre Operation unary_op ist auf den Bereich von [first1, last1) definierten angewendet. In der zweiten Version die binäre Operation binary_op ist auf Paare von Elementen aus zwei Bereichen eingesetzt: ein durch [first1, last1) und der andere Anfang an first2 definiert .
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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Inhaltsverzeichnis

[Bearbeiten] Parameter

first1, last1 - der erste, zu transformierende Elementbereich
first2 - der Beginn des zweiten, zu transformierenden Elementbereichs
d_first - der Beginn des Zielbereichs, kann gleich first1 oder first2 sein
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.

[Bearbeiten] Rückgabewert

Ausgabeiterator auf das Element nach dem letzten Element transformiert .
Original:
output iterator to the element past the last element transformed.
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[Bearbeiten] Komplexität

1)
genau std::distance(first1, last1) Anwendungen unary_op
Original:
exactly std::distance(first1, last1) applications of unary_op
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2)
genau std::distance(first1, last1) Anwendungen binary_op
Original:
exactly std::distance(first1, last1) applications of binary_op
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[Bearbeiten] Anforderungen

unary_op und binary_op haben keine Nebenwirkungen. (bis C + +11)
Original:
unary_op and binary_op have no side effects. (bis C + +11)
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unary_op und binary_op nicht entwerten keine Iteratoren, einschließlich der Ende Iteratoren oder zu modifizieren Elementen der Bereiche beteiligt. (seit 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. (seit C++11)
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Die Absicht ist es, diesen Anforderungen parallel oder out-of-order Implementierungen std::transform ermöglichen. Um eine Funktion zu einer Sequenz in Ordnung anzuwenden, verwenden 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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[Bearbeiten] Mögliche Implementierung

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;
}

[Bearbeiten] Beispiel

Der folgende Code verwendet transformieren, um eine Zeichenfolge in Großbuchstaben mit dem toupper Funktion konvertieren:
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

[Bearbeiten] Siehe auch

 Wendet eine Funktion auf eine Reihe von Elementen an
(Funktions-Template) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/algorithm/transform&oldid=31764“