fdec

A collection of macros for generating fixed-size fixed-point numeric types that exactly fit your domain. The types are fully equipped for performing mathematical computations and are easy to use.

With a simple macro call you get a type that:

• has no representation errors in the range, defined by the type parameters,
• supports arithmetic operations: +, -, *, /, %, <<, >>,
• comes with mathematical functions: abs(), powi(), sqrt(),
• has special values NaN and ±Infinity, and uses them instead of panicing,
• provides basic mathematical constants,
• seamlessly interacts with Rust's primitive types,
• converts values to/from byte arrays,
• creates values and performs math operations on stack, avoiding heap allocations.

When to Use

You should probably give fdec a try if:

• you need primitive types like i256 or i1408, which Rust doesn't provide,
• your business domain is not tolerant to representation errors that may add up during computations (like working with money in finance),
• other libraries that provide decimal numbers are not fast enough for you when it comes to doing math,
• you need to store lots of decimal numbers, and you'd prefer it to be memory-efficient,
• you're just curious to see how it works.

How to Use

Add the dependency on fdec to your Cargo.toml:

[dependencies]
fdec = "0.3.1"

Import it at your crate's root with the macro_use attribute:

#[macro_use]
extern crate fdec;

Add custom numeric types to your project by calling fdec* macros:

fdec64! {               // Use 64-bit units
    module bigdec,      // Put all the generated code into the `bigdec` module
    name BigDec,        // The name for the generated type
    length 5,           // 5 * 64-bit units = 320 bits to store numbers
    scale 50            // Use 50 decimal places
}

Example

Here we define the Decimal structure that represents 160-bit numbers with 30 decimal places.

#[macro_use]
extern crate fdec;

fdec32! {            // Use 32-bit units
    module dec,      // Put all the generated code into the `dec` module
    name Decimal,    // Name the main struct `Decimal`
    length 5,        // 5 * 32-bit units = 160 bits to store numbers
    scale 30         // Use 30 decimal places
}

use dec::*;          // Bring the generated stuff to the scope

fn main() {
    // Use it
    let a = Decimal::one();
    let b = Decimal::from(14);
    let c = dec!(9);
    let result = a + 30 * (b / c).powi(3);
    println!("{} + 30 * ({} / {})^3 = {}", a, b, c, result);
    // 1 + 30 * (14 / 9)^3 = 113.92181069958847736625514403278
}

More examples come with the crate's source code:

• Many ways to create values: creation.rs
• Compute Fibonacci numbers: fibonacci.rs
• Calculate square root with high precision: sqrt.rs