Pretty print floats

[0xbentang]

In the span I'll like to add a field to show some elapsed time, for example:

info!(elapsed = now.elapsed().as_secs_f64(), "Finished");

However it'll print a float like 0.088599778 which is not particularly human friendly.

Right now I can do

info!(elapsed = format!("{:.4}s", now.elapsed().as_secs_f64()), "Finished");

To limit the no. of decimal places, as well as a suffix s to indicate it is in seconds. But format! will allocate a String every time and it'll not be efficient if I have a lot of logs? Is there any other way to print this more efficiently?

[mladedav]

It's not the best thing ever, but you can create a struct PrettyFloat(f64) and implement std::fmt::Debug on it so that it uses exactly the format you want.

Then you should be able to info!(x = debug(PrettyFloat(y))); and it'll use your Debug implementation.

You could also do the same thing with Display if you'd prefer.

[0xbentang]

Thank you this works nicely!