xref: /third_party/rust/crates/minimal-lexical/README.md

minimal-lexical
===============

This is a minimal version of [rust-lexical](https://github.com/Alexhuszagh/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](mailto:ahuszagh@gmail.com) or [Twitter](https://twitter.com/KardOnIce), 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](https://github.com/Alexhuszagh/rust-lexical).

**Table Of Contents**

- [Getting Started](#getting-started)
- [Recipes](#recipes)
- [Algorithms](#algorithms)
- [Platform Support](platform-support)
- [Minimum Version Support](minimum-version-support)
- [Changelog](#changelog)
- [License](#license)
- [Contributing](#contributing)

# Getting Started

First, add the following to your `Cargo.toml`.

```toml
[dependencies]
minimal-lexical = "0.2"
```

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

```rust
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
```

# Recipes

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:
```json
1.e7
```

Therefore, to use the library, you need functionality that extracts the significant digits to pass to `create_float`. Please see [simple-example](https://github.com/Alexhuszagh/minimal-lexical/blob/master/examples/simple.rs) for a simple, annotated example on how to use minimal-lexical as a parser.

# Algorithms

For an in-depth explanation on the algorithms minimal-lexical uses, please see [lexical-core#string-to-float](https://github.com/Alexhuszagh/rust-lexical/tree/master/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.

# Changelog

All changes are documented in [CHANGELOG](CHANGELOG).

# License

Minimal-lexical is dual licensed under the Apache 2.0 license as well as the MIT license. See the [LICENSE.md](LICENSE.md) file for full license details.

# Contributing

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.