created_at2021-04-27 23:04:12.608012
updated_at2021-10-04 10:53:11.629475
descriptionFast float parsing conversion routines.
Alexander Huszagh (Alexhuszagh)




This is a minimal version of rust-lexical, meant to allow efficient round-trip float parsing. minimal-lexical implements a correct, fast float parser.

Due to the small, stable nature of minimal-lexical, it is also well-adapted to private forks. If you do privately fork minimal-lexical, I recommend you contact me via email or Twitter, so I can notify you of feature updates, bug fixes, or security vulnerabilities, as well as help you implement custom feature requests. I will not use your information for any other purpose, including, but not limited to disclosing your project or organization's use of minimal-lexical.

minimal-lexical is designed for fast compile times and small binaries sizes, at the expense of a minor amount of performance. For improved performance, feel free to fork minimal-lexical with more aggressive inlining.

Similar Projects

For a high-level, all-in-one number conversion routines, see rust-lexical.

Table Of Contents

Getting Started

First, add the following to your Cargo.toml.

minimal-lexical = "0.2"

Next, to parse a simple float, use the following:

extern crate minimal_lexical;

// Let's say we want to parse "1.2345".
// First, we need an external parser to extract the integer digits ("1"),
// the fraction digits ("2345"), and then parse the exponent to a 32-bit
// integer (0). 
// Warning:
// --------
//  Please note that leading zeros must be trimmed from the integer,
//  and trailing zeros must be trimmed from the fraction. This cannot
//  be handled by minimal-lexical, since we accept iterators
let integer = b"1";
let fraction = b"2345";
let float: f64 = minimal_lexical::parse_float(integer.iter(), fraction.iter(), 0);
println!("float={:?}", float);    // 1.235


You may be asking: where is the actual parser? Due to variation in float formats, and the goal of integrating utility for various data-interchange language parsers, such functionality would be beyond the scope of this library.

For example, the following float is valid in Rust strings, but is invalid in JSON or TOML:


Therefore, to use the library, you need functionality that extracts the significant digits to pass to create_float. Please see simple-example for a simple, annotated example on how to use minimal-lexical as a parser.


For an in-depth explanation on the algorithms minimal-lexical uses, please see lexical-core#string-to-float.

Platform Support

minimal-lexical is tested on a wide variety of platforms, including big and small-endian systems, to ensure portable code. Supported architectures include:

  • x86_64 Linux, Windows, macOS, Android, iOS, FreeBSD, and NetBSD.
  • x86 Linux, macOS, Android, iOS, and FreeBSD.
  • aarch64 (ARM8v8-A) Linux, Android, and iOS.
  • armv7 (ARMv7-A) Linux, Android, and iOS.
  • arm (ARMv6) Linux, and Android.
  • mips (MIPS) Linux.
  • mipsel (MIPS LE) Linux.
  • mips64 (MIPS64 BE) Linux.
  • mips64el (MIPS64 LE) Linux.
  • powerpc (PowerPC) Linux.
  • powerpc64 (PPC64) Linux.
  • powerpc64le (PPC64LE) Linux.
  • s390x (IBM Z) Linux.

minimal-lexical should also work on a wide variety of other architectures and ISAs. If you have any issue compiling minimal-lexical on any architecture, please file a bug report.

Minimum Version Support

Minimal-lexical is tested to support Rustc 1.36+, including stable, beta, and nightly. Please report any errors compiling a supported lexical version on a compatible Rustc version. Please note we may increment the MSRV for compiler versions older than 18 months, to support at least the current Debian stable version, without breaking changes.


All changes are documented in CHANGELOG.


Minimal-lexical is dual licensed under the Apache 2.0 license as well as the MIT license. See the file for full license details.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in minimal-lexical by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Commit count: 68

cargo fmt