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std::accumulate

From cppreference.com
 
 
 
Defined in header <numeric>
template< class InputIterator, class T >
T accumulate( InputIterator first, InputIterator last, T init );
(1)
template< class InputIterator, class T, class BinaryOperation >

T accumulate( InputIterator first, InputIterator last, T init,

              BinaryOperation op );
(2)

Computes the sum of the given value init and the elements in the range [first, last). The first version uses operator+ to sum up the elements, the second version uses the given binary function op.

Contents

[edit] Parameters

first, last - the range of elements to sum
init - initial value of the sum
op - binary operation function object that will be applied.

The signature of the function should be equivalent to the following:

Ret fun(const Type1 &a, const Type2 &b);

The signature does not need to have const &.
The type  Type1 must be such that an object of type T can be implicitly converted to  Type1. The type  Type2 must be such that an object of type InputIterator can be dereferenced and then implicitly converted to  Type2. The type  Ret must be such that an object of type T can be assigned a value of type  Ret. ​

[edit] Return value

The sum of the given value and elements in the given range.

[edit] Possible implementation

[edit] Example

#include <iostream>
#include <vector>
#include <numeric>
#include <string>
 
int multiply(int x, int y)
{
    return x*y;
}
 
std::string magic_function(std::string res, int x)
{
    if (x > 5) {
         res += "b";
    } else {
         res += "s";
    }
    return res;
}
 
int main()
{
    std::vector<int> v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
 
    int sum = std::accumulate(v.begin(), v.end(), 0);
    int product = std::accumulate(v.begin(), v.end(), 1, multiply);
    std::string magic = std::accumulate(v.begin(), v.end(), std::string(), 
                                        magic_function);
 
    std::cout << sum << '\n'
              << product << '\n'
              << magic << '\n';
}

Output:

55
3628800
sssssbbbbb

[edit] See also

computes the differences between adjacent elements in a range
(function template) [edit]
computes the inner product of two ranges of elements
(function template) [edit]
computes the partial sum of a range of elements
(function template) [edit]