#integer #nightly #bounded #refinement

nightly no-std ranged_integers

An integer restricted to a compile-time defined bounds driven by const generics

8 unstable releases (3 breaking)

Uses new Rust 2021

0.6.0 Sep 24, 2021
0.5.1 Sep 14, 2021
0.4.2 Jul 29, 2021
0.3.1 Jul 26, 2021

#666 in Rust patterns

28 downloads per month

MIT license

75KB
1.5K SLoC

Ranged integers [nightly only]

Documentation at docs.rs

Sudoku example

Changelog

Provides a generic type Ranged<MIN, MAX> representing an integer within a specified range. It automatically chooses the data size guided by the range specified (so Ranged<-50, 50> is of 1 byte while Ranged<-20_000, 100_000> is of 4 bytes) and supports the arithmetic operations with automatic bound recalculation and range iteration / fixed-size array indexing.

The conversion and arithmetic functions catch the errors such as possible overflow and zero division at compile time.

Example

#![allow(incomplete_features)]
#![feature(adt_const_params, generic_const_exprs)]

extern crate ranged_integers;
use ranged_integers::*;

// Consider a simple race game. The player rolls a
// die and then moves forward, backward or forward
// with the double speed according to some rules.

enum MoveType {MoveForward, DoubleSpeed, MoveBackward}

// Get a die roll using a standard random number generator
fn roll_die(rng: &mut dyn rand::RngCore) -> Ranged<1, 6> {
    let random: u8 = rng.gen();
        // The consistency is proved at compile time:
        // r!(6) means Ranged<6,6> with the value 6
        // r!(1) means Ranged<1,1> with the value 1
        // u8 % Ranged<6, 6> = Ranged<0, 5>
        // Ranged<0, 5> + Ranged<1, 1> = Ranged<1, 6>
    random % r!(6) + r!(1)
}

// Calculate where the player must move
// The result fits the range -6..=12
fn move_player(
    mtype: MoveType, 
    dice_points: Ranged<1, 6>
) -> Ranged<-6, 12>
{
    match move_type {
        MoveType::MoveForward => {
            // Expand 1..=6 to -6..=12
            dice_points.expand()
        }
        MoveType::DoubleSpeed => {
            let mv = dice_points*r!(2); // Ranged<2, 12>
            mv.expand() // Expand to -6..=12
        }
        MoveType::MoveBackward => {
            let mv = -dice_points; // Ranged<-6, -1>
            mv.expand() // Expand to -6..=12
        }
    }
}

No runtime deps