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std::inner_product

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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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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 search operations (on sorted ranges)
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Set operations (on sorted ranges)
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Heap operations
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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 InputIt1, class InputIt2, class T >

T inner_product( InputIt1 first1, InputIt1 last1,

                 InputIt2 first2, T value );
(1)
template<

    class InputIt1,
    class InputIt2,
    class T,
    class BinaryOperation1,
    class BinaryOperation2
> T inner_product( InputIt1 first1, InputIt1 last1,
                   InputIt2 first2, T value,
                   BinaryOperation1 op1,

                   BinaryOperation2 op2 );
(2)
Berechnet innere Produkt (dh die Summe der Produkte) des Bereichs [first1, last1) und einen Bereich beginnend bei first2. Die erste Version verwendet operator* zum Produkt des Elements Paare und operator+ berechnen, summieren die Produkte verwendet die zweite Version op2 und op1 für diese Aufgaben bzw. .
Original:
Computes inner product (i.e. sum of products) of the range [first1, last1) and another range beginning at first2. The first version uses operator* to compute product of the element pairs and operator+ to sum up the products, the second version uses op2 and op1 for these tasks respectively.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

first1, last1 -
die erste Reihe von Elementen
Original:
the first range of elements
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first2 -
der Beginn der zweiten Reihe von Elementen
Original:
the beginning of the second range of elements
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value -
anfängliche Wert der Summe der Produkte
Original:
initial value of the sum of the products
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op1 - binary operation function object that will be applied.
Diese Funktion übernimmt ein Wert, der durch op2 zurückgegeben und den aktuellen Wert des Akkumulators und produziert einen neuen Wert in dem Akkumulator gespeichert werden .
Original:
This function takes a value returned by op2 and the current value of the accumulator and produces a new value to be stored in the accumulator.
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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 types  Type1 and  Type2 must be such that objects of types T and Type3 can be implicitly converted to  Type1 and  Type2 respectively. The type  Ret must be such that an object of type T can be assigned a value of type  Ret. ​

op2 - binary operation function object that will be applied.
Diese Funktion nimmt einen Wert aus jedem Bereich und erzeugt einen neuen Wert .
Original:
This function takes one value from each range and produces a new value.
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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 types  Type1 and  Type2 must be such that objects of types InputIt1 and InputIt2 can be dereferenced and then implicitly converted to  Type1 and  Type2 respectively. The type  Ret must be such that an object of type Type3 can be assigned a value of type  Ret. ​

Type requirements
-
InputIt1, InputIt2 must meet the requirements of InputIterator.
-
T must meet the requirements of CopyAssignable and CopyConstructible.

[Bearbeiten] Rückgabewert

Das innere Produkt von zwei Bereichen .
Original:
The inner product of two ranges.
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[Bearbeiten] Mögliche Implementierung

First version
template<class InputIt1, class InputIt2, class T>
T inner_product(InputIt1 first1, InputIt1 last1,
                InputIt2 first2, T value)
{
    while (first1 != last1) {
         value = value + *first1 * *first2;
         ++first1;
         ++first2;
    }
    return value;
}
Second version
template<class InputIt1, class InputIt2,
         class T,
         class BinaryOperation1, class BinaryOperation2>
T inner_product(InputIt1 first1, InputIt1 last1,
                InputIt2 first2, T value,
                BinaryOperation1 op1
                BinaryOperation2 op2)
{
    while (first1 != last1) {
         value = op1(value, op2(*first1, *first2));
         ++first1;
         ++first2;
    }
    return value;
}

[Bearbeiten] Beispiel

#include <numeric>
#include <iostream>
#include <vector>
#include <functional>
int main()
{
    std::vector<int> a{0, 1, 2, 3, 4};
    std::vector<int> b{5, 4, 2, 3, 1};
 
    int r1 = std::inner_product(a.begin(), a.end(), b.begin(), 0);
    std::cout << "Inner product of a and b: " << r1 << '\n';
 
    int r2 = std::inner_product(a.begin(), a.end(), b.begin(), 0,
                                std::plus<int>(), std::equal_to<int>());
    std::cout << "Number of pairwise matches between a and b: " <<  r2 << '\n';
}

Output:

Inner product of a and b: 21
Number of pairwise matches between a and b: 2

[Bearbeiten] Siehe auch

fasst eine Reihe von Elementen
Original:
sums up a range 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]