fhex

Hex float conversion for Rust: ToHex for formatting, FromHex for parsing.

Uses the IEEE 754 hexadecimal floating-point format (±0xh.hhhp±d)—the same format used by C's %a printf specifier, Java's Double.toHexString(), and the WebAssembly text format.

Documentation · Crates.io

Usage

[dependencies]
fhex = "2.0"

use fhex::{ToHex, FromHex};

// Formatting
let hex = 3.0_f64.to_hex();
assert_eq!(hex, "0x1.8p+1");

// Parsing
let value = f64::from_hex("0x1.8p+1").unwrap();
assert_eq!(value, 3.0);

// Round-trip
let original = std::f64::consts::PI;
let roundtrip = f64::from_hex(&original.to_hex()).unwrap();
assert_eq!(original, roundtrip);

Format

Floating point numbers are represented as ±0xh.hhhp±d, where:

• ± is the sign (- for negative, omitted for positive)
• 0x is the hex prefix
• h.hhh is the significand in hexadecimal
• p±d is the exponent in decimal (base 2)

Special values:

• ±0x0p+0 for zero
• ±inf for infinity
• nan for quiet NaN
• nan:0x... for NaN with payload (signalling NaN)

Parsing Features

• Underscores for readability: 0x1_000p+0
• NaN payloads preserved: nan:0x123
• Case-insensitive: INF, NaN, 0X1P+0
• Whitespace trimmed

Output Differences vs Other Languages

• Go's %x: Uses ±Inf and NaN (capitalised), zero-pads exponent to 2 digits
• C++ std::hexfloat: No special NaN payload handling

License

Apache-2.0