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std::basic_istream::putback - cppreference.com

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basic_istream& putback( char_type ch );

Coloca o personagem ch de volta para o fluxo de entrada de modo que o próximo personagem extraído será ch.

Original:

Puts the character ch back to the input stream so the next extracted character will be ch.

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Primeiro limpa eofbit, em seguida, se comporta como UnformattedInputFunction. Depois de construir e verificar o objeto de sentinela, se rdbuf() não é nulo, chama rdbuf()->sputbackc(ch), que chama rdbuf()->pbackfail(ch) se ch não é igual o personagem mais recentemente extraído.

Original:

First clears eofbit, then behaves as UnformattedInputFunction. After constructing and checking the sentry object, if rdbuf() is not null, calls rdbuf()->sputbackc(ch), which calls rdbuf()->pbackfail(ch) if ch does not equal the most recently extracted character.

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Se rdbuf() é nulo ou se rdbuf->sputbackc(ch) retornos Traits::eof(), chama setstate(badbit).

Original:

If rdbuf() is null or if rdbuf->sputbackc(ch) returns Traits::eof(), calls setstate(badbit).

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Em qualquer caso, define o gcount() contador a zero.

Original:

In any case, sets the gcount() counter to zero.

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Parâmetros

(Nenhum)

Original:

(none)

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Valor de retorno

*this

Exemplo

demonstra a diferença entre a modificação e não modificar putback ()

Original:

demonstrates the difference between modifying and non-modifying putback()

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#include <sstream>
#include <iostream>
int main()
{
    std::stringstream s1("Hello, world"); // IO stream
    s1.get();
    if(s1.putback('Y')) // modifies the buffer
        std::cout << s1.rdbuf() << '\n';
    else
        std::cout << "putback failed\n";

    std::istringstream s2("Hello, world"); // input-only stream
    s2.get();
    if(s2.putback('Y')) // cannot modify input-only buffer
        std::cout << s2.rdbuf() << '\n';
    else
        std::cout << "putback failed\n";

    s2.clear();
    if(s2.putback('H')) // non-modifying putback
        std::cout << s2.rdbuf() << '\n';
    else
        std::cout << "putback failed\n";
}

Saída:

Yello, world
putback failed
Hello, world

Veja também

unextracts um personagem

Original:

unextracts a character

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(função pública membro) [edit]

lê o próximo caractere sem extraí-lo

Original:

reads the next character without extracting it

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(função pública membro) [edit]