STL Sample for accumulate, copy, vector::push_back Functions

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

SUMMARY

The sample code below illustrates how to use the accumulate, copy, and vector::push_back STL functions in Visual C++.

MORE INFORMATION

Required Header

   <numeric>
   <functional>

Prototype

   template<class InputIterator, class _TYPE> inline
      _TYPE accumulate(InputIterator first, InputIterator last, _TYPE init)

   template<class InputIterator, class _TYPE, class BinaryOperator> inline
      _TYPE accumulate(InputIterator first, InputIterator last, _TYPE init,
                       BinaryOperator binary_op)

Description

The accumulate function initializes an accumulator acc with an initial value init and then modifies it with acc = acc + *i or acc = binary_op(acc,*i) for every iterator i in the range [first, last) in order.

Normally, the accumulate function is used to sum the numeric elements of a vector. However, it can also be used to do other useful work such as concatenate a vector of strings.

Sample Code

   ///////////////////////////////////////////////////////////////////////
   //
   // Compile options needed: /GX
   //
   // accumulate.cpp : Demonstrates the use of accumulate()
   //
   // Description of accumulate(first,last,init)
   //                accumulate(first,last,init,binary_op):
   //
   //    Initializes the accumulator acc with the initial value init
   //        acc = init
   //    and then modifies it with
   //        acc  =  acc + *i
   //    or
   //        acc = binary_op(acc, *i)
   //    for every iterator i in the range [first, last) in order.
   //
   // Written by Shaun Miller
   // of Microsoft Product Support Services, Languages Developer Support.
   // Copyright (c) 1996 Microsoft Corporation. All rights reserved.
   ///////////////////////////////////////////////////////////////////////

   // turn off warning about symbols too long for debugger
   #pragma warning (disable : 4786)

   #include <iostream>
   #include <numeric>
   #include <functional>
   #include <vector>
   #include <iterator>
   #include <string>

   typedef vector < float, allocator < float > > FloatArray;
   typedef vector < string, allocator < string > > StringArray;
   typedef ostream_iterator <float, char, char_traits <char> >
   FloatOstreamIt;

   void main ()
   {
       // a vector of floats
       FloatArray rgFA;

       // an ostream iterator that outputs a float to cout terminated
       // by a space
       FloatOstreamIt OstreamIt(cout," ");

       // Initialize the array to 1,1/2,1/3,...
       for (int i=0; i<10; i++) rgFA.push_back(1.0f/(i+1));

       // Print the array
       copy(rgFA.begin(),rgFA.end(),OstreamIt);
       cout << endl;

       // Sum the array
       cout << "The sum of 1 + 1/2 + 1/3 + ... + 1/10 is "
            << accumulate(rgFA.begin(),rgFA.end(),0.0f)
            << endl;

       // Compute the product of the array
       cout << "The product of 1 * 1/2 * 1/3 * ... * 1/10 is "
            << accumulate(rgFA.begin(),rgFA.end(),1.0f,times<float>())
            << endl;

       // Initialize array of strings
       StringArray rgs;
       rgs.push_back("This ");
       rgs.push_back("is ");
       rgs.push_back("one ");
       rgs.push_back("sentence. ");

       // Concatenate the strings in the array & print the sentence
       cout << "The concatenated vector of strings: "
            << accumulate(rgs.begin(),rgs.end(),string(""))
            << endl;
   }

1 0.5 0.333333 0.25 0.2 0.166667 0.142857 0.125 0.111111 0.1 The sum of 1 + 1/2 + 1/3 + ... + 1/10 is 2.92897 The product of 1 * 1/2 * 1/3 * ... * 1/10 is 2.75573e-007 The concatenated vector of strings: This is one sentence.

REFERENCES

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