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std::operator<<,>> - cppreference.com

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Definido no cabeçalho `<string>`

`template <class CharT, class Traits, class Allocator> std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const std::basic_string<CharT, Traits, Allocator>& str);`	(1)

`template <class CharT, class Traits, class Allocator> std::basic_istream<CharT, Traits>& operator>>(std::basic_istream<CharT, Traits>& is, std::basic_string<CharT, Traits, Allocator>& str);`	(2)

1)

Primeiro, constrói um objeto std::basic_ostream::sentry, que libera o empate () 'd fluxo, se necessário, e verifica se há erros. Se o objeto sentinela retorna false, sai imediatamente.

Original:

First, constructs a std::basic_ostream::sentry object, which flushes the tie()'d stream if necessary and checks for errors. If the sentry object returns false, exits immediately.

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Depois disso, se o objecto de sentinela true retornos, determina o formato de saída de acolchoamento da mesma maneira como o estágio 3 de

num_put::put()

.

Original:

Afterwards, if the sentry object returns true, determines the output format padding in the same manner as stage 3 of

num_put::put()

.

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Em seguida, armazena cada personagem da seqüência resultante (o conteúdo de str mais estofo) para o fluxo de saída os como se chamando os.rdbuf()->sputn(seq, n), onde n=std::max(os.width(), str.size())

Original:

Then stores each character from the resulting sequence (the contents of str plus padding) to the output stream os as if by calling os.rdbuf()->sputn(seq, n), where n=std::max(os.width(), str.size())

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Finalmente, chama os.width(0).

Original:

Finally, calls os.width(0).

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2)

Primeiro, constrói um objeto std::basic_istream::sentry, que libera o empate () 'd fluxo, se necessário, extratos e descarta todos os personagens principais espaços em branco, a menos que a bandeira ios_base::skipws foi cancelado, e verifica se há erros. Se o objeto sentinela retorna false, sai imediatamente.

Original:

First, constructs a std::basic_istream::sentry object, which flushes the tie()'d stream if necessary, extracts and discards all leading whitespace characters unless the ios_base::skipws flag was cleared, and checks for errors. If the sentry object returns false, exits immediately.

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Depois, se os retornos de sentinela objeto true, limpa str com str.erase()

Original:

Afterwards, if the sentry object returns true, clears str with str.erase()

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Em seguida, lê caracteres de is e acrescenta-lhes a str como se por str.append(1, c), até que uma das seguintes condições torna-se verdade:

Original:

Then reads characters from is and appends them to str as if by str.append(1, c), until one of the following conditions becomes true:

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N caracteres são lidos, onde N é is.width() se is.width() > 0, caso contrário, é N str.max_size()
Original:
N characters are read, where N is is.width() if is.width() > 0, otherwise N is str.max_size()
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a condição de fim de arquivo ocorre no is fluxo
Original:
the end-of-file condition occurs in the stream is
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std::isspace(c,is.getloc()) é verdade para o próximo caractere c em is (este personagem espaços em branco permanece no fluxo de entrada).
Original:
std::isspace(c,is.getloc()) is true for the next character c in is (this whitespace character remains in the input stream).
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Se nenhum dos caracteres são extraídos então std::ios::failbit é definido em is, que pode lançar std::ios_base::failure.

Original:

If no characters are extracted then std::ios::failbit is set on is, which may throw std::ios_base::failure.

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Finalmente, chama os.width(0) e destrói o objeto std::basic_istream::sentry.

Original:

Finally, calls os.width(0) and destroys the std::basic_istream::sentry object.

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Exceções

1)

pode lançar std::ios_base::failure se uma exceção é lançada durante a saída.

Original:

may throw std::ios_base::failure if an exception is thrown during output.

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2)

pode lançar std::ios_base::failure se não são personagens extraídos de is (por exemplo, o fluxo está no final do arquivo, ou seja constituído por espaços em branco apenas), ou se uma exceção é lançada durante a entrada.

Original:

may throw std::ios_base::failure if no characters are extracted from is (e.g the stream is at end of file, or consists of whitespace only), or if an exception is thrown during input.

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Parâmetros

os	-	um fluxo de saída de caractere Original: a character output stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is	-	um fluxo de entrada de caracteres Original: a character input stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
str	-	a string a ser inserido ou extraído Original: the string to be inserted or extracted The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Valor de retorno

1) os

2) is

Exemplo

#include <iostream>
#include <string>

int main()
{
    std::string greeting = "Hello, whirled!"
    std::cout << greeting << '\n';
}

Saída: