Q168185: HOWTO: STL Sample for gslice::(length, start, stride) Functions
Article: Q168185
Product(s): Microsoft C Compiler
Version(s): winnt:4.2,5.0,6.0
Operating System(s):
Keyword(s): _IK kbVC420 kbVC500 kbVC600
Last Modified: 05-MAY-2001
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The information in this article applies to:
- The Standard C++ Library, used with:
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0
- Microsoft Visual C++, 32-bit Professional Edition, version 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
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SUMMARY
=======
The sample code below illustrates how to use the gslice::length, gslice::start,
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 vs. later revisions. The relevant
sections of code below compile conditionally based upon the value of _MSC_VER.
MORE INFORMATION
================
Required Header
---------------
<valarray>
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
//
// <filename> : 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 <iostream> // for i/o functions
#include <valarray> // for valarray
using namespace std;
#if _MSC_VER > 1020 // if VC++ version is > 4.2
using namespace std; // std c++ libs implemented in std
#endif
void main()
{
// Initialize string 1 to contain "Hello World!", and string 2 to
// contain "There".
valarray<char> string1("Hello World!", 12);
valarray<char> 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
--------------
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.
REFERENCES
==========
Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library
Reference.
(c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Yeong-Kah
Tam, Microsoft Corporation
Additional query words: STL STLSample length, start, stride
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Keywords : _IK kbVC420 kbVC500 kbVC600
Technology : kbVCsearch kbAudDeveloper kbVCLibrary
Version : winnt:4.2,5.0,6.0
Issue type : kbhowto
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