How to find how many places from left the dot appears in a flot/double?

[afg45]

On Thursday, 30 December 2021 at 09:03:58 UTC, rempas wrote:
> Let's say that I have the following float/double: 137.837
>
> How can I find how many places from left the dot appears? So in 
> this example I want to take either three or four (depending on 
> how you think it). Does anyone knows how I can do that and can 
> explain it to me?

See the https://en.wikipedia.org/wiki/Common_logarithm fpr the 
explanations.

```
import std.stdio, std.math;

void main(string[] args)
{
     alias numDigits = (f) => log10(f + 0.5).ceil();
}
```