Question

I’m trying to write an algorithm to find the minimum number of precision digits to show at least one significant figure using .Net string formatter.

eg.

Value      Precision wanted:
-----      -----------------
10         0
 1         0
 0.1       1
 0.99      1   
 0.01      2
 0.009     3

(don’t care about further digits, only the first, hence 0.99 only need a precision of 1.)

The best I can come up with is:

int precision = (int)Math.Abs(Math.Min(0, Math.Floor(Math.Log10(value))));

This works fine but I can’t help thinking there’s a more elegant solution. Can any maths gurus help me out?

Answer 1

Slightly shorter:

int precision = (int)Math.Max(0, -Math.Floor(Math.Log10(value)));