Print float with actual float size

Question

Im trying to print out a format of lets say x levels of accuracy meaning it should print if x = 10

float foo;
printf("levels of accuracy %.10f", foo);

What i've tried: I already have the math to convert the x to the desired decimal place. something like..

int multiplier = 10;
float initialaccuracy = 1.0;
float threshold = initialaccuracy / ((float)(pow(multiplier, accuracy)));

What I want to know:

How do i use the format of that x into the printf so if i pick x= 4 it would be %.4f or if i pick 15 it would be %.15f, without hardcoding those values just using it of whatever i pass in?

duplicate: https://stackoverflow.com/questions/16413609/printf-variable-number-of-decimals-in-float — seleciii44, Oct 02 '19 at 03:51

score 3 · Accepted Answer · answered Oct 02 '19 at 03:01

3

You can put a * in place of the precision specifier and pass it as a separate parameter:

int accuracy = 10;
printf("levels of accuracy %.*f", accuracy, foo);

answered Oct 02 '19 at 03:01

dbush

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score 0 · Answer 2 · answered Oct 02 '19 at 03:13

0

Or, build your format string 'on the fly'...

char fmt[99];
sprintf(fmt,"levels of accuracy %%.%df",accuracy);
printf(fmt,foo);

answered Oct 02 '19 at 03:13

ChuckCottrill

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The first seemed a bit easier to understand but I appreciate the response. Ima look into sprintf haven’t used it yet. – Oct 03 '19 at 04:12

Print float with actual float size

2 Answers2