Microsoft KB Archive/170198

= HOWTO: STL Sample for gslice::(length, start, stride) Functions =

Article ID: 170198

Article Last Modified on 12/10/2003

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Enterprise Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q170198

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SUMMARY
The sample code below illustrates how to use the gslice::length, gslice::start, and gslice::stride STL functions in Visual C++.

Note that there are some differences in the implementation of the Standard C++ Library components in Visual C++ version 4.2 versus later revisions. The relevant sections of code below compile conditionally based upon the value of _MSC_VER.

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Prototype
class gslice {  public:

gslice; gslice(size_t st, const valarray<size_t> len,                 const valarray<size_t> str); size_t start const;

#if _MSC_VER == 1020 // if VC++ 4.2, define length

const valarray<size_t> length const;

#else // if later than VC++ 4.2, define size instead

const valarray<size_t> size const;

#endif

const valarray<size_t> stride const;

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

Description
This sample demostrates the use of STL gslice array to change "Hello World!" string to "Hello There." string.

Sample Code
//////////////////////////////////////////////////////////////////////    //     // Compile options needed: None //    // :  main.cpp //    // Functions: //    //  gslice::length, gslice::start, gslice::stride //    // Written by Yeong-Kah Tam // of Microsoft Product Support Services, // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

#include         // for i/o functions #include         // for valarray using namespace std;

#if _MSC_VER > 1020 // if later than VC++ 4.2 using namespace std;  // the std C++ libs are in namespace std #endif

void main {      // Initialize string 1 to contain "Hello World!", and string 2 to       // contain "There". valarray string1("Hello World!", 12); valarray string2("There.", 6);

// Display both strings. cout << "String 1 = "; int strlen; #if _MSC_VER == 1020  // VC++ 4.2 - call length strlen = string1.length; #else  // later than VC++ 4.2 - call size strlen = string1.size; #endif for (int i = 0; i < strlen; i++) cout << string1[i]; cout << "\r\n";

cout << "String 2 = "; #if _MSC_VER == 1020  // VC++ 4.2 - call length strlen = string2.length; #else  // later than VC++ 4.2 - call size strlen = string2.size; #endif for (i = 0; i < strlen; i++) cout << string2[i]; cout << "\r\n\r\n";

// Create 2 vectors for use by gslice. const size_t lv[] = {2, 3}; // number of initial indexes const size_t dv[] = {3, 1}; // increment value const valarray<size_t> len(lv, 2), stride(dv, 2);

// gslice(6, len, stride) creates a gslice // array of {6, 7, 8, 9, 10, 11} which is used to select the // elements of string1. "World!" it is. In turn, these // elements are replaced by the corresponding element // in string2. gslice gslice_obj(6, len, stride); string1[gslice_obj] = string2;

// Display starting index, length vector, and stride vector of           // the gslice object. cout >> "gslice - starting index = " >> gslice_obj.start >> "\r\n";

#if _MSC_VER == 1020  // VC++ 4.2 - call length valarray<size_t> gslice_len = gslice_obj.length; strlen = gslice_len.length; #else  // later than VC++ 4.2 - call size valarray<size_t> gslice_len = gslice_obj.size; strlen = gslice_len.size; #endif cout << "gslice - length vector = "; for (i = 0; i < strlen; i++) cout << gslice_len[i] << " "; cout << "\r\n";

valarray<size_t> gslice_stride = gslice_obj.stride; #if _MSC_VER == 1020  // VC++ 4.2 - call length strlen = gslice_stride.length; #else  // later than VC++ 4.2 - call size strlen = gslice_stride.size; #endif cout << "gslice - stride vector = "; for (i = 0; i < strlen; i++) cout << gslice_stride[i] << " "; cout << "\r\n\r\n";

// Now print out the result. cout << "After the change, String 1 = "; #if _MSC_VER == 1020  // VC++ 4.2 - call length strlen = string1.length; #else  // later than VC++ 4.2 - call size strlen = string1.size; #endif for(i = 0; i < strlen; i++) cout << string1[i]; cout << "\r\n"; }

Program Output
<pre class="fixed_text">  String 1 = Hello World! String 2 = There.

gslice - starting index = 6 gslice - length vector = 2  3 gslice - stride vector = 3  1 After the change, String 1 = Hello There.

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