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

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Editions, version 4.2

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;
   };

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 // later than version 4.2
    using 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   // 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

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.