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std::inner_product

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C++
 
Biblioteca algoritmo
Funções
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Functions
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Não modificar operações de seqüência
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Non-modifying sequence operations
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Modificando operações de seqüência
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Modifying sequence operations
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Particionamento operações
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Partitioning operations
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Operações de classificação (em intervalos ordenados)
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Sorting operations (on sorted ranges)
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Binários operações de busca (em intervalos ordenados)
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Binary search operations (on sorted ranges)
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Definir operações (em intervalos ordenados)
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Set operations (on sorted ranges)
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Operações de pilha
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Heap operations
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Mínimo / máximo de operações
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Minimum/maximum operations
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Operações numéricas
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Numeric operations
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(C++11)
inner_product
C biblioteca
Original:
C library
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Definido no cabeçalho <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)
Calcula produto interno (ou seja, soma de produtos) do [first1, last1) faixa e outra faixa no início first2. A primeira versão utiliza operator* para calcular o produto dos pares de elementos e operator+ para resumir os produtos, a segunda versão utiliza op2 e op1 para estas tarefas, respectivamente.
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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Índice

[editar] Parâmetros

first1, last1 -
o primeiro intervalo de elementos
Original:
the first range of elements
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first2 -
o início da segunda gama de elementos
Original:
the beginning of the second range of elements
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value -
valor inicial da soma dos produtos
Original:
initial value of the sum of the products
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op1 - binary operation function object that will be applied.
Esta função tem um valor retornado por op2 e o valor actual do acumulador e produz um novo valor a ser armazenado no acumulador .
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.
Esta função tem um valor de cada faixa e produz um novo valor .
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.

[editar] Valor de retorno

O produto interno de duas cadeias.
Original:
The inner product of two ranges.
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[editar] Possível implementação

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;
}

[editar] Exemplo

#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';
}

Saída: 

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

[editar] Veja também
resume uma série de elementos
Original:
sums up a range of elements
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(modelo de função) [edit]
calcula a soma parcial de um conjunto de elementos
Original:
computes the partial sum of a range of elements
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(modelo de função) [edit]
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