kinogaki-float-text

The shortest decimal text that reads back as the same f64, fast.

The digits are the shortest that round-trip, and of those the closest to the exact value (ties to even): the same digits as Rust's {:e} (tests/against_std.rs) except at exact ties, where we round to even (as Ryu and zmij do), and the text is zmij's byte for byte. The digits come from one 128-bit scaling (src/shortest.rs), written eight at a time. The text is plain decimal when the value's scientific exponent E is in -5..=15 (123.456, 0.00001, always with a .: 1.0), and d.ddde±E outside (1.5e+16, 1e-6).