Article ID: 170198
Article Last Modified on 12/10/2003
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
- Microsoft Visual C++ 6.0 Enterprise Edition
- Microsoft Visual C++ 6.0 Professional Edition
- Microsoft Visual C++ 6.0 Standard Edition
This article was previously published under Q170198
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.
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 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<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.
Additional query words: STL STLSample length start stride (c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Yeong-Kah Tam,
Keywords: kbhowto KB170198
