float

import std::fmt::float; · source

Float formatting lives here rather than in core::primitives because it needs libm, and keeping libc out of core matters more. The API is extension methods on the primitives.

f64#

implement f64 {
    is_negative_zero(&this) -> boolean;
    to_buf(&this, buffer: u8*) -> u64;
    to_buf_with(&this, buffer: u8*, decimals: u64) -> u64;
    to_buf_roundtrip(&this, buffer: u8*) -> u64;
}

const F64_MAX_DIGITS: u64 = 32;

Method	Notes
to_buf(buffer)	Fixed-point with six fractional digits. Buffer must hold at least F64_MAX_DIGITS (32) bytes.
to_buf_with(buffer, decimals)	Caller-chosen precision.
to_buf_roundtrip(buffer)	The shortest decimal string that re-parses to the identical bit value. f64 only.
is_negative_zero()

Values beyond |v| >= 1e16 or below 0 < |v| < 1e-4 switch to scientific notation, so no precision disappears into a giant zero prefix or a run of trailing zeros. NaN, both infinities, and both zeros are handled explicitly — negative zero prints as -0 so the sign is not lost.

to_buf is a first-cut formatter: correct for human-readable output but not round-trippable, since the fixed six decimals silently truncate (3.141592653589793 becomes 3.141593). Anything that must preserve the value — JSON serialization, notably — should use to_buf_roundtrip, which tries 15, then 16, then 17 significant digits and returns the first that re-parses exactly. Typical values stay compact: 0.1, not 0.10000000000000001.

f32#

implement f32 {
    to_buf(&this, buffer: u8*) -> u64;
    to_buf_with(&this, buffer: u8*, decimals: u64) -> u64;
    is_negative_zero(&this) -> boolean;
}

The same fixed-point writers at single precision. There is no to_buf_roundtrip for f32; widen to f64 for a round-trippable rendering.

parse_f64#

function parse_f64(s: string) -> Option<f64>;

parse_f64 is the reverse, with C strtod semantics: skip leading whitespace, read the longest valid float prefix, decimal or scientific, no hex floats. It returns None when there is no numeric prefix. Strip digit separators (_) before calling — strtod stops at them.

Integer formatting is on the primitives themselves in core::primitives, and integer parsing goes through TryFrom<Str> in collections::str.