STL-----------accumulate

 
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template <class InputIterator, class T>
   T accumulate ( InputIterator first, InputIterator last, T init );
template <class InputIterator, class T, class BinaryOperation>
   T accumulate ( InputIterator first, InputIterator last, T init,
                  BinaryOperation binary_op );

Accumulate values in range

Returns the result of accumulating all the values in the range [first,last) to init.

The default operation is to add the elements up, but a different operation can be specified as binary_op.

The behavior of this function template is equivalent to:

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template <class InputIterator, class T> T accumulate ( InputIterator first, InputIterator last, T init ) { while ( first!=last ) init = init + *first++; // or: init=binary_op(init,*first++) for the binary_op version return init; }

Parameters

first, last

Input iterators to the initial and final positions in a sequence. The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.

init

Initial value for the accumulator.

binary_op

Binary operation taking an object of type T as first argument and an element in the range as second. This can either be a pointer to a function or an object whose class overloads operator(). The operation is expected to return a value of type T.

Return value

The result of accumulating init and all the elements in the range [first,last).

Example

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// accumulate example #include <iostream> #include <functional> #include <numeric> using namespace std; int myfunction (int x, int y) {return x+2*y;} struct myclass { int operator()(int x, int y) {return x+3*y;} } myobject; int main () { int init = 100; int numbers[] = {10,20,30}; cout << "using default accumulate: "; cout << accumulate(numbers,numbers+3,init); cout << endl; cout << "using functional's minus: "; cout << accumulate (numbers, numbers+3, init, minus<int>() ); cout << endl; cout << "using custom function: "; cout << accumulate (numbers, numbers+3, init, myfunction ); cout << endl; cout << "using custom object: "; cout << accumulate (numbers, numbers+3, init, myobject ); cout << endl; return 0; }

 

#include <iostream>
#include <functional>
#include <numeric>
using namespace std;

int myfunction (int x, int y) {return x+2*y;}
class myclass {
public: int operator()(int x, int y) {return x+3*y;}
} ;

int main () {
  int init = 100;
  int numbers[] = {10,20,30};

  cout << "using default accumulate: ";
  cout << accumulate(numbers,numbers+3,init);
  cout << endl;

  cout << "using functional's minus: ";
  cout << accumulate (numbers, numbers+3, init, minus<int>() );
  cout << endl;

  cout << "using custom function: ";
  cout << accumulate (numbers, numbers+3, init, myfunction );
  cout << endl;

  cout << "using custom object: ";
  myclass myobject1;
  cout << accumulate (numbers, numbers+3, init, myobject1);
  cout << endl;

  return 0;
}

 

 

Output:

using default accumulate: 160 using functional's minus: 40 using custom function: 220 using custom object: 280