Fix #216

[Pat-Lafon]

This pr attempts to specify the output value of printing a float. A first pass of this is added to the documentation of the floating point extension. brili and brilirs have been modified to be compliant. The tests/benchmarks which output floats have also been updated.

[sampsyo]

Awesome; looks perfect!! I just tweaked the docs a bit for precision (and moved the text to a new section just about printing).

I was going to suggest that we not include trailing zeroes, because C printf and Python string formatting make this easy with the g specifier:

>>> '{:.17f}'.format(.5)
'0.50000000000000000'
>>> '{:.17g}'.format(.5)
'0.5'

…but it looks like Rust does not make this easy to do (see rust-lang/rust#29472) so that's probably too much trouble.

[Pat-Lafon]

Seems like this was somewhat discussed more recently in rust-lang/rfcs#2729 but they didn't go so far as to fully implement g behavior. If this is something you would prefer, it naively seems like a relatively straight forward change for brilirs.

If it's just a matter of trailing zeros, then https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=3ea18aef3548196ad33d8c6aa386364f seems reasonable.

If there is other behavior to be aware of, then there is atleast one crate that gives the desired behavior https://crates.io/crates/gpoint .

[sampsyo]

Ah, good digging!! Honestly I think it's totally cool to use this zero-having output… at the very least it's simple to specify. We can always revisit if someone eventually gets super annoyed staring at 1.00000000000000000 instead of 1.0. 😃