Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

 
transform
 
 - Applies an operation to a range of values in a collection and stores the result.
 
 
 

SYNOPSIS

 
 
#include <algorithm>
template <class InputIterator, class OutputIterator,

class UnaryOperation>

OutputIterator

    transform (InputIterator first, InputIterator last,

OutputIterator result, UnaryOperation op);

template <class InputIterator1, class InputIterator2,

class OutputIterator, class BinaryOperation>

OutputIterator

    transform (InputIterator1 first1, InputIterator1 last1,

InputIterator2 first2, OutputIterator result,
BinaryOperation binary_op);
 
 
 

DESCRIPTION

 
 
The transform algorithm has two forms. The first form applies unary operation op to each element of the range [first, last), and sends the result to the output iterator result. For example, this version of transform could be used to square each element in a vector. If the output iterator (result) is the same as the input iterator used to traverse the range, transform performs its transformation in place. 
 
The second form of transform applies a binary operation, binary_op, to corresponding elements in the range [first1, last1) and the range that begins at first2, and sends the result to result.   For example, transform can be used to add corresponding elements in two sequences, and store the set of sums in a third. The algorithm assumes, but does not check, that the second sequence has at least as many elements as the first sequence. Note that the output iterator result can be a third sequence, or either of the two input sequences. 
 
Formally, transform assigns through every iterator i in the range [result, result + (last1 - first1)) a new corresponding value equal to:
 
op(∗(first1 + (i - result))
 
or
 
binary_op(∗(first1 + (i - result), ∗(first2 + (i - result)))
 
transform returns result + (last1 - first1).   op and binary_op must not have any side effects. result may be equal to first in case of unary transform, or to first1 or first2 in case of binary transform. 
 
 
 

COMPLEXITY

 
 
Exactly last1 - first1 applications of op or binary_op are performed. 
 
 
 

EXAMPLE

//
// trnsform.cpp
//
#include <functional>
#include <deque>
#include <algorithm>
#include <iostream>
#include <iomanip>
 
using namespace std;
 
int main()

{

 
//Initialize a deque with an array of ints
int arr1[5] = {99, 264, 126, 330, 132};
int arr2[5] = {280, 105, 220, 84, 210};
deque<int> d1(arr1+0, arr1+5), d2(arr2+0, arr2+5);
 
//Print the original values
cout << "The following pairs of numbers: "

<< endl << "     ";

deque<int>::iterator i1;
for(i1 = d1.begin(); i1 != d1.end(); i1++)

cout << setw(6) << ∗i1 << " ";

cout << endl << "     ";
for(i1 = d2.begin(); i1 != d2.end(); i1++)

cout << setw(6) << ∗i1 << " ";

 
// Transform the numbers in the deque to their
// factorials and store in the vector
transform(d1.begin(), d1.end(), d2.begin(),

d1.begin(), multiplies<int>());

 
//Display the results
cout << endl << endl;
cout << "Have the products: " << endl << "     ";
for(i1 = d1.begin(); i1 != d1.end(); i1++)

cout << setw(6) << ∗i1 << " ";

return 0;

}
 

Program Output
 
 
 

 
The following pairs of numbers:

99    264    126    330    132

280    105    220     84    210

Have the products:
27720  27720  27720  27720  27720
 
 
 

WARNINGS

 
 
If your compiler does not support default template parameters, then you always need to supply the Allocator template argument. For instance, you need to write:
 
deque<int, allocator<int> >
 
instead of:
 
deque<int>
 
If your compiler does not support namespaces, then you do not need the using declaration for std. 
 

Rogue Wave Software  —  Last change: 02 Apr 1998