DOCUMENT:Q170199  05-MAY-2001  [visualc]
TITLE   :HOWTO: STL Sample for slice::(length, start, stride) Functions
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:4.2,5.0,6.0
OPER/SYS:
KEYWORDS:_IK kbVC500 kbVC600

======================================================================
-------------------------------------------------------------------------------
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 
-------------------------------------------------------------------------------

SUMMARY
=======

The sample code below illustrates how to use the slice::length, slice::start,
and slice::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 slice
      {
      public:

         slice();
         slice(size_t st, size_t len, size_t str);
         size_t start() const;

      #if _MSC_VER == 1020 // version 4.2 - declare length()

         size_t length() const;

      #else // later than version 4.2, length changed to size()

         size_t size() const;

      #endif

         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 demonstrates the use of STL slice array to change "Hello World!"
string to "Hello There." string.

Sample Code
-----------

       ////////////////////////////////////////////////////////////////////// 
       // 
       // Compile options needed: None
       // 
       // <filename> :  main.cpp
       // 
       // Functions:
       // 
       //  slice::length, slice::start, slice::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   // version 4.2 - call length
          strlen = string1.length();
       #else   // later than 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   // version 4.2 - call length
          strlen = string2.length();
       #else   // later than 4.2 - call size
          strlen = string2.size();
       #endif
          for (i = 0; i < strlen; i++)
             cout << string2[i];
          cout << "\r\n\r\n";

          // slice(6, 6, 1) creates a slice 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.
          slice slice_obj(6, 6, 1);
          string1[slice_obj] = string2;

          // Display starting index, length,
          // and stride of the slice object.
          cout << "slice - starting index = " << slice_obj.start();
               cout << "\r\n";
       #if _MSC_VER == 1020   // version 4.2 - call length
          cout << "slice - length = " << slice_obj.length() << "\r\n";
       #else   // later than 4.2 - call size
          cout << "slice - length = " << slice_obj.size() << "\r\n";
       #endif
          cout << "slice - stride = " << slice_obj.stride() << "\r\n";
          cout << "\r\n";

          // Now print out the result.
          cout << "After the change, String 1 = ";
       #if _MSC_VER == 1020   // version 4.2 - call length
          strlen = string1.length();
       #else   // later than 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.

   slice - starting index = 6
   slice - length = 6
   slice - stride = 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          : _IK kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : winnt:4.2,5.0,6.0
Issue type        : kbhowto

=============================================================================

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