std::accumulate

 

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Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle  (C++11) unique unique_copy
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is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
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is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
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max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

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

op must not have side effects.	(until C++11)
op must not invalidate any iterators, including the end iterators, or modify any elements of the range involved.	(since C++11)

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 InputIt 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. ​
Type requirements
- InputIt must meet the requirements of InputIterator.
- T must meet the requirements of CopyAssignable and CopyConstructible.

Return value

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

Possible implementation

First version
template<class InputIt, class T> T accumulate(InputIt first, InputIt last, T init) { for (; first != last; ++first) { init = init + *first; } return init; }
Second version
template<class InputIt, class T, class BinaryOperation> T accumulate(InputIt first, InputIt last, T init, BinaryOperation op) { for (; first != last; ++first) { init = op(init, *first); } return init; }

Example

Run this code

#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)
{
    return res += (x > 5) ? "b" : "s";
}
 
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

See also

adjacent_difference	computes the differences between adjacent elements in a range (function template)
inner_product	computes the inner product of two ranges of elements (function template)
partial_sum	computes the partial sum of a range of elements (function template)