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std::inner_product

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< cpp‎ | algorithm

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C++
 
Bibliothèque d'algorithmes
Fonctions
Original:
Functions
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Non-modification de la séquence des opérations
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Non-modifying sequence operations
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Modification de la séquence des opérations
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Modifying sequence operations
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Des opérations de partitionnement
Original:
Partitioning operations
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Opérations de tri (sur les gammes triés)
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Sorting operations (on sorted ranges)
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is_sorted (C++11)
is_sorted_until (C++11)
sort
Opérations binaires de recherche (sur les gammes triés)
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Binary search operations (on sorted ranges)
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Définir les opérations (sur les gammes triés)
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Set operations (on sorted ranges)
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Opérations Heap
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Heap operations
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Minimum / maximum de fonctionnement
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Minimum/maximum operations
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Opérations numériques
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Numeric operations
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iota (C++11)
accumulate
inner_product
Bibliothèque C
Original:
C library
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Déclaré dans l'en-tête <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)
Calcule produit scalaire (soit la somme des produits) de l'[first1, last1) gamme et un autre début de la plage à first2. La première version utilise pour calculer operator* produit des paires d'éléments et operator+ de résumer les produits, la deuxième version utilise op2 et op1 pour ces tâches respectivement .
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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Sommaire

[modifier] Paramètres

first1, last1 -
la première gamme d'éléments
Original:
the first range of elements
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first2 -
le début de la seconde gamme d'éléments
Original:
the beginning of the second range of elements
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value -
valeur initiale de la somme des produits
Original:
initial value of the sum of the products
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op1 - binary operation function object that will be applied.
Cette fonction prend une valeur renvoyée par op2 et la valeur de courant de l'accumulateur et produit une nouvelle valeur à stocker dans l'accumulateur .
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.
Cette fonction prend une valeur de chaque gamme et produit une nouvelle valeur .
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.

[modifier] Retourne la valeur

Le produit scalaire de deux gammes .
Original:
The inner product of two ranges.
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[modifier] Mise en œuvre possible

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;
}

[modifier] Exemple

#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';
}

Résultat : 

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

[modifier] Voir aussi
résume un ensemble d'éléments
Original:
sums up a range of elements
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(fonction générique) [edit]
calcule la somme partielle d'une série d'éléments
Original:
computes the partial sum of a range of elements
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(fonction générique) [edit]
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