STL Sample for the find_if Function

ID: Q156299

The information in this article applies to:

The Standard C++ Library, included with:
- Microsoft Visual C++ 32-bit Edition, version 4.2

SUMMARY

The sample code below illustrates how to use the find_if STL function in Visual C++.

MORE INFORMATION

Required Header


<algorithm>

Prototype


   template<class InputIterator, class T, class Predicate> inline
            InputIterator find_if(InputIterator first,
                                  InputIterator last,
                                  Predicate predicate)

NOTE: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description

The find_if algorithm locates the first element in the range [first, last) that causes the predicate to return true and returns the iterator positioned at that element, or last if no such element was found.

Sample Code


////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// findif.cpp : Illustrates how to use the find_if function.
// 
// Functions:
// 
//   find_if  - locate the first element in a range that satisfies
//              a predicate.
// 
// Written by Kalindi Sanghrajka
// of Microsoft Product Support Services,
// Software Core Developer Support.
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <algorithm>
#include <iostream>

// returns true if n is an odd number
int IsOdd( int n)
{
    return n % 2 ;
}

void main()
{
    const int ARRAY_SIZE = 8 ;
    int IntArray[ARRAY_SIZE] = { 1, 2, 3, 4, 4, 5, 6, 7 } ;
    int *location ;   // stores the position of the first
                      // element that is an odd number
    int i ;

        // print content of IntArray
    cout << "IntArray { " ;
    for(i = 0; i < ARRAY_SIZE; i++)
        cout << IntArray[i] << ", " ;
    cout << " }" << endl ;

    // Find the first element in the range [first, last -1 ]
    // that is an odd number
    location = find_if(IntArray, IntArray + ARRAY_SIZE, IsOdd) ;

    //print the location of the first element
    // that is an odd number
    if (location != IntArray + ARRAY_SIZE)  // first odd element found
        cout << "First odd element " << *location
             << " is at location " << location - IntArray << endl;
    else         // no odd numbers in the range
        cout << "The sequence does not contain any odd numbers"
             << endl ;
    }

Output:

IntArray { 1, 2, 3, 4, 4, 5, 6, 7, }

First odd element 1 is at location 0

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.

Additional query words: STL count_if

Keywords : kbcode STLIss
Version : winnt:
Platform : winnt
Issue type : kbhowto