Tracking Issue for general floating point formatting

[mxxo]

This is a tracking issue for general human-readable floating point formatting akin to C's printf("%g").

RFCs:

Link	Description
RFC 844	Original request for a %g-style format
RFC 2729	Detailed RFC by @ExpHP proposing a {:g?} Debug formatter following the stabilization of {:x?}.

Open questions:

1. Format specifier and trait (:g | :g? | :#?). Extend Debug or introduce LowerGen, UpperGen formatting traits?

From RFC 2729:

2. The precise format is subject to heavy bikeshedding.
3. When should the format be considered final? On stabilization of {:g?}? On stabilization of {:g} if it occurs?
4. Public API for this and RFC 2226

Links:

Pre-RFC discussion: https://internals.rust-lang.org/t/pre-rfc-draft-g-or-floating-points-for-humans/9110

Related crates:

• float-pretty-print by @vi
• 3photons-rust by @HadrienG2 implements a %g-like formatter.
• sad_monte_carlo by @droudy implements a %g-like formatter.

[jonas-schievink]

rust-lang/rfcs#2729 has not been accepted yet

[droudy]

@droundy