another question about stl and sprintf

[avi123]

If I have for example a double holding the value 128.65 and I want to present it as 128.650000

than I can do

sprinf(szStr,"%.10f,myDouble)

I tried using your advice and use std::stringstream
but what I managed to do is getting 0000128.65

what I did is:


std::stringstream buffer;
buffer.fill('0');
buffer << std::setw(nLen) << dValue;//nLen is the required length
//in this example it's 10
*psDest = buffer.str();



Can you pls show me how to do that?

thanks
avi

[Gabriel Fleseriu]

#include <sstream>
#include <iomanip>

int main()
{
    std::stringstream ss;
    double d = 218.65;
    ss<<std::setfill('0')<<std::left<<std::setw(10)<<d<<std::endl;
    std::cout<<ss.str();
    return 0;
}

[avi123]

what do you think is better
using this or using sprintf
(I mean performance)

thanks

[jfaust]

You should only worry about performance if you've discovered a performance problem. Your concern should be maintenance, not performance.

This is better.

Jeff

[Graham]

#include <string>
#include <sstream>
#include <iomanip>

using namespace std;

string write_double(double d, int width, int precision)
{
    stringstream ss;
    ss << setw(10) << setprecision(6) << d;
    return ss.str();
}

int main()
{
    string s = write_double(128.65, 10, 6);
}

There's also a manipulator for doing the equivalent of the g, f and e format specifiers, but I can't remember what it is offhand (the default is to output like %g).