std::slice - cppreference.com

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Definido no cabeçalho `<valarray>`

`class slice;`

std::slice é a classe selector que identifica um subconjunto de std::valarray semelhante a fatia BLAS. Um objecto da std::slice tipo prende três valores: o índice de partida, o passo, e o número total de valores no subconjunto. Objectos de std::slice tipo podem ser usados como índices com operator[] valarray de.

Original:

std::slice is the selector class that identifies a subset of std::valarray similar to BLAS slice. An object of type std::slice holds three values: the starting index, the stride, and the total number of values in the subset. Objects of type std::slice can be used as indexes with valarray's operator[].

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Funções de membro


(constructor)	constrói uma fatia Original: constructs a slice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro)

start	acede ao início da fatia Original: accesses the start of the slice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro)

size	acede ao tamanho da fatia Original: accesses the size of the slice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro)

stride	acessa o tranco da fatia Original: accesses the stride of the slice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro)

Exemplo

Barebones classe Matrix valarray apoiado com uma função traçar cálculo .

Original:

Barebones valarray-backed Matrix class with a traçar calculating function.

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#include <iostream>
#include <valarray>
class Matrix {
    std::valarray<int> data;
    int dim;
 public:
    Matrix(int r, int c) : data(r*c), dim(c) {}
    int& operator()(int r, int c) {return data[r*dim + c];}
    int trace() const {
        return data[std::slice(0, dim, dim+1)].sum();
    }
};
int main()
{
    Matrix m(3,3);
    int n = 0;
    for(int r=0; r<3; ++r)
       for(int c=0; c<3; ++c)
           m(r, c) = ++n;
    std::cout << "Trace of the matrix (1,2,3) (4,5,6) (7,8,9) is " << m.trace() << '\n';
}

Saída:

Trace of the matrix (1,2,3) (4,5,6) (7,8,9) is 15

Veja também


operator[]	get / set elemento valarray, uma fatia ou máscara Original: get/set valarray element, slice, or mask The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro) [edit]

gslice	fatia generalizada de uma valarray: índice inicial, conjunto de comprimentos, conjunto de passos Original: generalized slice of a valarray: starting index, set of lengths, set of strides The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe) [edit]

slice_array	proxy para um subconjunto de uma valarray após a aplicação de uma fatia Original: proxy to a subset of a valarray after applying a slice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (modelo de classe) [edit]