floating point number formatting question

[ahmd]

Very nice! I didn't know that * is a special symbol. You can probably shrink it down to even 2 lines of code if you consolidate the 'n' variable. And we can probably save some on CPU cycles if we replace second division (nValueMult100 &#37; 100) with (nValueMult100 < 100).

[GeoRanger]

You might be able to gain control and flexibility if you print it as two integers:

#include <math.h>
void NoTrailingZerosPrintf(double const dValue, unsigned short nDecimalPlaces)
{
    int const nFactor    = static_cast<int>(pow(10.0, nDecimalPlaces));
    int const iFixed     = static_cast<int>(dValue * nFactor + (dValue > 0 ? 0.5 : -0.5));
    int       iFraction  = abs(iFixed % nFactor);
    while     (iFraction > 0 && iFraction % 10 == 0) { iFraction /= 10; --nDecimalPlaces; }
    printf    (iFraction == 0 ? "%d\n" : "%d.%0*d\n", iFixed / nFactor, nDecimalPlaces, iFraction);
}
 
int main(int argc,char* argv[])
{
    NoTrailingZerosPrintf(1.0000   , 2);  // Test case 1.1
    NoTrailingZerosPrintf(1.30     , 2);  // Test case 1.2
    NoTrailingZerosPrintf(1.32     , 2);  // Test case 1.3
    NoTrailingZerosPrintf(1.38     , 2);  // Test case 1.4
    NoTrailingZerosPrintf(1.322    , 2);  // Test case 1.5
    NoTrailingZerosPrintf(1.325    , 2);  // Test case 1.6
    NoTrailingZerosPrintf(-37.09   , 3);  // Test case 2.1
    NoTrailingZerosPrintf(-37.09   , 1);  // Test case 2.2
    NoTrailingZerosPrintf(-37.00005, 4);  // Test case 2.3
    NoTrailingZerosPrintf(-37.00004, 4);  // Test case 2.4
    NoTrailingZerosPrintf(-37.00005, 5);  // Test case 2.5
    NoTrailingZerosPrintf(1.998    , 2);  // Test case 3.1
    return 0;
}

Output:

1
1.3
1.32
1.38
1.32
1.33
-37.09
-37.1
-37.0001
-37
-37.00005
2