std::endl
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Definido no cabeçalho <ostream> | ||
template<class CharT, class Traits > std::basic_ostream<charT,traits>& endl(std::basic_ostream<CharT, Traits>& os ); | ||
Insere um caractere de fim de linha para o
os seqüência de saída e libera-lo como se chamando os.put(os.widen('\n')) seguido por os.flush(). Original:
Inserts a endline character into the output sequence
os and flushes it as if by calling os.put(os.widen('\n')) followed by os.flush(). The text has been machine-translated via Google Translate.
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Esta é uma saída de somente manipulador de I / O, que pode ser chamada com uma indicação tal como para qualquer out << std::endl
out de std::basic_ostream tipo.Original:
This is an output-only I/O manipulator, it may be called with an expression such as out << std::endl for any
out of type std::basic_ostream.The text has been machine-translated via Google Translate.
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Índice |
[editar]Notas
Este manipulador pode ser utilizado para produzir uma linha de saída, imediatamente, por exemplo, ao exibir a saída de um processo de longa duração, o registro da atividade de vários segmentos ou registrar a atividade de um programa que pode falhar inesperadamente. Um esvaziamento explícito de std::cout também é necessária antes de uma chamada para std::system, se o processo gerado executa qualquer tela de I / O (um exemplo comum é std::system("pause") no Windows). Na maioria dos outros habituais interativos / S cenários, std::endl é redundante quando usado com std::cout porque qualquer entrada de std::cin, saída para std::cerr, ou término do programa obriga uma chamada para std::cout.flush(). Uso de std::endl no lugar de '\n', incentivado por algumas fontes, pode degradar significativamente o desempenho saída.
Original:
This manipulator may be used to produce a line of output immediately, e.g. when displaying output from a long-running process, logging activity of multiple threads or logging activity of a program that may crash unexpectedly. An explicit flush of std::cout is also necessary before a call to std::system, if the spawned process performs any screen I/O (a common example is std::system("pause") on Windows). In most other usual interactive I/O scenarios, std::endl is redundant when used with std::cout because any input from std::cin, output to std::cerr, or program termination forces a call to std::cout.flush(). Use of std::endl in place of '\n', encouraged by some sources, may significantly degrade output performance.
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Em muitas implementações, a saída padrão é a linha-buffered, e '\n' escrita provoca uma descarga de qualquer maneira, a menos que std::cout.sync_with_stdio(false) foi executado. Nessas situações,
endl desnecessário só degrada o desempenho de saída de arquivo não, a saída padrão.Original:
In many implementations, standard output is line-buffered, and writing '\n' causes a flush anyway, unless std::cout.sync_with_stdio(false) was executed. In those situations, unnecessary
endl only degrades the performance of file output, not standard output.The text has been machine-translated via Google Translate.
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Os exemplos de código neste follow Bjarne Stroustrup wiki em Flushing a saída padrão apenas quando necessário.
Original:
The code samples on this wiki follow Bjarne Stroustrup in flushing the standard output only where necessary.
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Quando uma linha incompleta de saída tem de ser lavada, o manipulador std::flush podem ser utilizados.
Original:
When an incomplete line of output needs to be flushed, the std::flush manipulator may be used.
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Quando todos os caracteres de saída precisa ser lavada, o manipulador std::unitbuf pode ser usado.
Original:
When every character of output needs to be flushed, the std::unitbuf manipulator may be used.
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[editar]Parâmetros
| os | - | referência ao fluxo de saída Original: reference to output stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
[editar]Valor de retorno
os (referência ao fluxo após a manipulação)Original:
os (reference to the stream after manipulation)The text has been machine-translated via Google Translate.
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[editar]Exemplo
Com \ n em vez de endl, o resultado seria o mesmo, mas não pode aparecer em tempo real .
Original:
With \n instead of endl, the output would be the same, but may not appear in real time.
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#include <iostream>#include <chrono>template<typename Diff>void log_progress(Diff d){std::cout<<std::chrono::duration_cast<std::chrono::milliseconds>(d).count()<<" ms passed"<< std::endl;}int main(){std::cout.sync_with_stdio(false);// on some platforms, stdout flushes on \nvolatileint sink=0; auto t1 = std::chrono::high_resolution_clock::now();for(int j=0; j<5;++j){for(int n=0; n<10000;++n)for(int m=0; m<20000;++m) sink += m*n;// do some workauto now = std::chrono::high_resolution_clock::now(); log_progress(now - t1);}}
Saída:
487 ms passed 974 ms passed 1470 ms passed 1965 ms passed 2455 ms passed
[editar]Veja também
controles se a saída é liberada após cada operação Original: controls whether output is flushed after each operation The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função) | |
libera o fluxo de saída Original: flushes the output stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (modelo de função) | |
sincroniza com o dispositivo de armazenamento subjacente Original: synchronizes with the underlying storage device The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (of std::basic_ostream função pública membro) | |
