accumulate, copy, and vector::push_back
Visual Studio 2005
Illustrates how to use the accumulate, copy, and vector::push_back Standard Template Library (STL) functions in Visual C++.
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
)
 Note |
|---|
| The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability. |
The accumulate STL 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 STL function is used to sum the numeric elements of a vector. However, it can also be used to do other useful work such as concatenating a vector of strings.
// accumulate.cpp
// compile with: /EHsc
//
// 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.
// 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>
using namespace std;
typedef vector < float > FloatArray;
typedef vector < string > StringArray;
typedef ostream_iterator <float, char, char_traits <char> > FloatOstreamIt;
int 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,multiplies<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 and print the sentence
cout << "The concatenated vector of strings: "
<< accumulate(rgs.begin(),rgs.end(),string(""))
<< endl;
}
