Microsoft KB Archive/157221

= STL Sample for the Predicate Version of lower_bound Function =

Article ID: 157221

Article Last Modified on 11/18/2003

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APPLIES TO


 * The Standard C++ Library
 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 4.2 Professional Edition

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This article was previously published under Q157221



SUMMARY
The sample code below illustrates how to use the predicate version of lower_bound STL function in Visual C++.



Prototype
template inline ForwardIterator lower_bound(ForwardIterator first,                                    ForwardIterator last,                                     const T& value,                                     Compare compare) NOTE: The class/parameter names in the prototype do not match the original version in the header file. They have been modified to improve readability.

Description
The lower_bound algorithm returns the first location in the sequence that value can be inserted such that the order of the sequence is maintained.

lower_bound returns an iterator positioned at the location that value can be inserted in the range [first..last), or returns last if no such position exists.

This version assumes the range [first..last) is sorted sequentially using the compare function.

Sample Code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // lower_bound.cpp : Illustrates how to use the lower_bound //                  function. // // Functions: // //   lower_bound : Return the lower bound within a range. // // 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 this warning
 * 1) pragma warning(disable: 4786)

using namespace std;
 * 1) include
 * 2) include
 * 3) include
 * 4) include

void main {   const int VECTOR_SIZE = 8 ;

// Define a template class vector of int typedef vector IntVector ;

//Define an iterator for template class vector of strings typedef IntVector::iterator IntVectorIt ;

IntVector Numbers(VECTOR_SIZE) ;

IntVectorIt start, end, it, location ;

// Initialize vector Numbers Numbers[0] = 4 ; Numbers[1] = 10; Numbers[2] = 70 ; Numbers[3] = 10 ; Numbers[4] = 30 ; Numbers[5] = 69 ; Numbers[6] = 96 ; Numbers[7] = 100;

start = Numbers.begin ;  // location of first // element of Numbers

end = Numbers.end ;      // one past the location // last element of Numbers

//sort Numbers using the function object less //lower_bound assumes that Numbers is sorted //using the "compare" (less in this case) //function sort(start, end, less ) ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// return the first location at which 10 can be inserted // in Numbers location = lower_bound(start, end, 10, less ) ;

cout << "First location element 10 can be inserted in Numbers is: " << location - start << endl ; } Output: Numbers { 4 10 10 30 69 70 96 100 } First location element 10 can be inserted in Numbers is: 1

