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accumulate
function template
<numeric>
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;
}
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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;
}
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Output:
using default accumulate: 160
using functional's minus: 40
using custom function: 220
using custom object: 280
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See also
| inner_product | Compute cumulative inner product of range (function template) |
| partial_sum | Compute partial sums of range (function template) |
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