i want to extract fractional part from a given double variable with exact precision.I m getting only upto 6 precision

Question

I'm trying to run this. I have tried fmod too. Nothing worked yet.

void main(){
    double a = 123.46566662;
    double frac = a - (long)a;
    printf("%f", frac);
}
//tried int64_t too   
// output is :.465667

Did you try changing the precision of `printf`? Like `%.10f`? — StoryTeller - Unslander Monica, Feb 16 '17 at 06:39
thanks it worked.any idea why it is not working without .10? — sociopath, Feb 16 '17 at 06:41

score 0 · Answer 1 · edited Feb 16 '17 at 07:51

0

Use .10f or .nf precision to get the desired precision. here n = number of precision. thanks to @StoryTeller

void main()  
{      
double a=123.46566662;  
double frac=a-(long)a;  
printf("%.10f",frac);  
} 

//output :.4656666200

edited Feb 16 '17 at 07:51

msc

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answered Feb 16 '17 at 07:00

sociopath

79
1
6

score 0 · Answer 2 · answered Feb 16 '17 at 07:20

The idea of "exact precision" is what gets your. Decimal fractions (generally) cannot be represented in a finite binary number. Much like there's no "exact" decimal fraction for a 2/3.

The best you can hope for is to have a "close enough" fractional part with an ever-higher precision based on your data type (think float vs. double).

If you do indeed have to get the "exact precision" I recommend you implement your own "precise" arithmetic, in which you store decimal numbers in decimal representation. Be it a string, a BCD, or an array of digits.

i want to extract fractional part from a given double variable with exact precision.I m getting only upto 6 precision

2 Answers2