Equivalent of %02d with std::stringstream?

I want to output an integer to a std::stringstream with the equivalent format of printf's %02d. Is there an easier way to achieve this than:

std::stringstream stream;
stre开发者_如何转开发am.setfill('0');
stream.setw(2);
stream << value;

Is it possible to stream some sort of format flags to the stringstream, something like (pseudocode):

stream << flags("%02d") << value;

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You can use the standard manipulators from <iomanip> but there isn't a neat one that does both fill and width at once:

stream << std::setfill('0') << std::setw(2) << value;

It wouldn't be hard to write your own object that when inserted into the stream performed both functions:

stream << myfillandw( '0', 2 ) << value;

E.g.

struct myfillandw
{
    myfillandw( char f, int w )
        : fill(f), width(w) {}

    char fill;
    int width;
};

std::ostream& operator<<( std::ostream& o, const myfillandw& a )
{
    o.fill( a.fill );
    o.width( a.width );
    return o;
}

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You can use

stream<<setfill('0')<<setw(2)<<value;

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You can't do that much better in standard C++. Alternatively, you can use Boost.Format:

stream << boost::format("%|02|")%value;

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Is it possible to stream some sort of format flags to the stringstream?

Unfortunately the standard library doesn't support passing format specifiers as a string, but you can do this with the fmt library:

std::string result = fmt::format("{:02}", value); // Python syntax

or

std::string result = fmt::sprintf("%02d", value); // printf syntax

You don't even need to construct std::stringstream. The format function will return a string directly.

Disclaimer: I'm the author of the fmt library.

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i think you can use c-lick programing.

you can use snprintf

like this

std::stringstream ss;
 char data[3] = {0};
 snprintf(data,3,"%02d",value);
 ss<<data<<std::endl;