std::inner_product
De cppreference.com
<metanoindex/>
<tbody> </tbody>| 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.The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
Parâmetros
| first1, last1 | - | o primeiro intervalo de elementos
Original: the first range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| first2 | - | o início da segunda gama de elementos
Original: the beginning of the second range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| value | - | valor inicial da soma dos produtos
Original: initial value of the sum of the products The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| 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. The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. The signature of the function should be equivalent to the following:
The signature does not need to have |
| 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. The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. The signature of the function should be equivalent to the following:
The signature does not need to have |
| Type requirements | ||
-InputIt1, InputIt2 must meet the requirements of InputIterator.
| ||
-T must meet the requirements of CopyAssignable and CopyConstructible.
| ||
Valor de retorno
O produto interno de duas cadeias.
Original:
The inner product of two ranges.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
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;
}
|
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