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

ID: Q170199

The information in this article applies to:

The Standard C++ Library, used with:
- Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0, 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

   #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.

Keywords : kbcode kbVC500 kbVC600 STLIss
Version : winnt:4.2,5.0,6.0
Platform : winnt
Issue type : kbhowto