for_each(3C++)

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

NAME

for_each

- Applies a function to each element in a range.

SYNOPSIS

#include <algorithm>
template <class InputIterator, class Function>
void for_each(InputIterator first, InputIterator last,

Function f);

DESCRIPTION

The for_each algorithm applies function f to all members of the sequence in the range [first, last), where first and last are iterators that define the sequence. Since this a non-mutating algorithm, the function f cannot make any modifications to the sequence, but it can achieve results through side effects (such as copying or printing). If f returns a result, the result is ignored.

COMPLEXITY

The function f is applied exactly last - first times.

EXAMPLE

//
// for_each.cpp
//
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>
using namespace std;

// Function class that outputs its argument times x

template <class Arg>
class out_times_x : private unary_function<Arg,void>

{

private:

Arg multiplier;

public:

out_times_x(const Arg& x) : multiplier(x) { }
void operator()(const Arg& x)

{ cout << x ∗ multiplier << " " << endl; }

};

int main()

{

int sequence[5] = {1,2,3,4,5};

// Set up a vector

vector<int> v(sequence,sequence + 5);

// Setup a function object

out_times_x<int> f2(2);

for_each(v.begin(),v.end(),f2); // Apply function

return 0;

}

Program Output

2
4
6
8
10

WARNINGS

If your compiler does not support default template parameters, then you always need to supply the Allocator template argument. For instance, you have to write:

vector<int, allocator<int> >

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.

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