std::accumulate
Defined in header
<numeric>
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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, |
(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
.
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(until C++11) |
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(since C++11) |
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 &. |
Type requirements | ||
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InputIt must meet the requirements of InputIterator .
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T must meet the requirements of CopyAssignable and CopyConstructible .
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[edit] Return value
The sum of the given value and elements in the given range.
[edit] Possible implementation
First version |
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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; } |
[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) { 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
[edit] See also
computes the differences between adjacent elements in a range (function template) |
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computes the inner product of two ranges of elements (function template) |
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computes the partial sum of a range of elements (function template) |