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std::accumulate

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Algorithm Bibliothek
Funktionen
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Functions
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Nicht-modifizierende Sequenz Operationen
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Non-modifying sequence operations
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Modifizierende Sequenz Operationen
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Modifying sequence operations
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Partitionierungsoperationen
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Partitioning operations
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Sortierung Operationen (auf sortierten Bereiche)
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Sorting operations (on sorted ranges)
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Binary Suchaktionen (auf sortierten Bereiche)
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Binary search operations (on sorted ranges)
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Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap-Operationen
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Heap operations
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Numerische Operationen
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iota(C++11)
accumulate
inner_product
C-Bibliothek
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C library
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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.

Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
das Spektrum der Elemente Summe
Original:
the range of elements to sum
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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.

[Bearbeiten] Rückgabewert

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

[Bearbeiten] Mögliche Implementierung

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

[Bearbeiten] Beispiel

#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

[Bearbeiten] Siehe auch

berechnet die Differenzen zwischen benachbarten Elementen in einer Reihe
Original:
computes the differences between adjacent elements in a range
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(Funktions-Template) [edit]
berechnet das innere Produkt von zwei Bereichen der Elemente
Original:
computes the inner product of two ranges of elements
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(Funktions-Template) [edit]
berechnet die Teilsumme von einer Reihe von Elementen
Original:
computes the partial sum of a range of elements
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(Funktions-Template) [edit]