Q156299: STL Sample for the find_if Function

Article: Q156299
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): _IK
Last Modified: 07-MAY-2001

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The information in this article applies to:

- The Standard C++ Library, included with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 4.2 
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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>
  using namespace std;

  // 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

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Keywords          : _IK 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : winnt:
Issue type        : kbhowto

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