Is there a function to round a float in C or do I need to write my own?

Question

Is there a function to round a float in C or do I need to write my own?

float conver = 45.592346543;

I would

Answer 1

There is a round() function, also fround(), which will round to the nearest integer expressed as a double. But that is not what you want.

I had the same problem and wrote this:

#include <math.h>

   double db_round(double value, int nsig)
/* ===============
**
** Rounds double <value> to <nsig> significant figures.  Always rounds
** away from zero, so -2.6 to 1 sig fig will become -3.0.
**
** <nsig> should be in the range 1 - 15
*/

{
    double     a, b;
    long long  i;
    int        neg = 0;


    if(!value) return value;

    if(value < 0.0)
    {
        value = -value;
        neg = 1;
    }

    i = nsig - log10(value);

    if(i) a = pow(10.0, (double)i);
    else  a = 1.0;

    b = value * a;
    i = b + 0.5;
    value = i / a;

    return neg ? -value : value;
}