Oxide Programming Language

Interpreted scripting language with a Rust influenced syntax. Latest release

Example programs

/// structs

struct Circle {                                // struct declaration
    pub radius: float,                         // public field
    center: Point,                             // private field
}

impl Circle {                                  // struct implementation
    const PI: float = 3.14159;                 // private associated constant

    pub fn new(r: float, c: Point) -> Self {   // public static method
        return Self {
            radius: r,
            center: c,
        };
    }
}

struct Point {
    pub x: int,
    pub y: int,
}

/// traits

trait Shape {                                   // trait declaration
    fn calc_area(self) -> float;                // trait methods are always public
}

impl Shape for Circle {                         // trait implementation
    fn calc_area(self) -> float {  
        return Self::PI * self.radius * self.radius;
    }
}

// program entry point
fn main() {                                     
    let a: Shape = Circle::new(200.0, Point { x: 1, y: 5 });
    let area = a.calc_area();                   
  
    println("circle area: " + area as str);     // type casting
}

/// enums

enum Ordering {
    Less,
    Equal,
    Greater
}

impl Ordering {
    pub fn compare(a: int|float, b: int|float) -> Self {
        return match true {
            a < b  => Self::Less,
            a == b => Self::Equal,
            a > b  => Self::Greater,
        };
    }
}

fn main() {
    let order = Ordering::compare(10, 5); // Ordering::Greater
}

/// sorting a vector using
/// insertion sort

fn insertion_sort(input: vec<int>) {
    for i in 1..input.len() {
        let cur = input[i];
        let mut j = i - 1;

        while input[j] > cur {
            let temp = input[j + 1];
            input[j + 1] = input[j];
            input[j] = temp;

            if j == 0 {
                break;
            }

            j -= 1;
        }
    }
}

fn main() {
    let input: vec<int> = vec[4, 13, 0, 3, -3, 4, 19, 1];
    insertion_sort(input);
    dbg(input); // [vec] [-3, 0, 1, 3, 4, 4, 13, 19]
}

More examples

Usage

Download the latest release and put the executable in your PATH.

USAGE:
    oxide [FLAGS] [ARGS]

FLAGS:
    -h, --help              Prints help
    -v, --version           Prints version
    -r, --repl              Run REPL
    -t, --allow-top-level   Allow top-level instructions

ARGS:
    <FILE>  Script file to run
    <ARGV>  Arguments passed to script

EXAMPLE:
    oxide script.ox arg1 arg2

Building from source

If your architecture is not supported by the pre-built binaries you can build the interpreter from the source code yourself. Make sure you have Rust installed.

git clone https://github.com/tuqqu/oxide-lang.git
cd oxide-lang
cargo +nightly install --path oxide-cli # creates a binary /.cargo/bin/oxide
                                        # to uninstall run `cargo uninstall oxide-cli`
# you can now run it with
oxide script.ox

Quick Overview

• Program Structure
• Variables and Type System
  • Mutability
  • Shadowing
  • Casting
  • Union Types
  • Type aliases
• Control Flow and Loops
  • If
  • Match
  • While
  • Loop
  • For
• Functions
  • Closures
• Structs
  • Public and Private
• Traits
• Enums
• Vectors
  • Range Expressions
• Constants
• Operators
  • Unary
  • Binary
• Comments
• Standard library

Program Structure

In Oxide, the entry point of a program is a function named main.

fn main() {
    // code goes here
}

On the top level only item (const, fn, struct, enum, trait, impl, type) declarations are allowed.

struct Foo {}

trait Bar {}

enum Foo {}

impl Bar for Foo {}

const C: int = 0;

fn baz() {}

type Foo = int;

Variables and Type System

Types and example values:

• nil: only nil value itself,
• bool: false, true,
• int: 1,
• float: 0.56,
• str: "string",
• fn(T) -> T: any function or lambda with this signature,
• vec<T>: vec[1, 2, 3, 4],
• any: any value,
• union types str | int | T | ...: any value of the types composing the union

user-defined types

• structs: Foo { bar: "bar" }
• enums: Foo::Bar
• type aliases type Foo = Bar;

See type system

Variables are typed either explicitly:

let x: int;                            // type = int
let nums: vec<int> = vec[1, 2];        // type = vec<int>
let jane: Person|nil = Person {        // union type = Person|nil
    name: "Jane" 
};  

// functions are their own type
let double: fn(int) -> int = fn (x: int) -> int { return x * 2; };
          //^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
          //     type                      lambda       

or their type implicitly inferred:

let x = vec["h", "i"];             // inferred as vec<str>
let dog = Dog::new("Good Boy");    // inferred as Dog
let ordering = Ordering::Less;     // inferred as Ordering
let f = fn (x: int) { ... };       // inferred as fn(int)

let x;                             // inferred as vec<int>
x = 0..=100;                       // the first time it is being assigned

Mutability

Variables are immutable by default:

let x = 100;
x += 1; //! error, x is immutable

To become mutable they must be defined with mut keyword.

let mut x: str = "hello";
x += " world"; // ok

Shadowing

Variables can be shadowed. Each variable declaration "shadows" the previous one:

let x: int|nil = 100;
let x: vec<int> = vec[1, 2];

Casting

Explicit type conversion, i.e. type casting, can be performed using the as keyword. Primitive types int, float, nil, bool, str can be cast to other primitive types.

let x = 32 as str;              // typeof(x) = str,  x = "32"
let x = "350" as int;           // typeof(x) = int,  x = 350
let x = 0.0 as bool;            // typeof(x) = bool, x = false

let x = 10;
"this is x: " + x as str;       // values must be cast to str for concatenation

Using non-primitives (vector vec<T>, function fn(T) -> T, enum, and struct types) will result in a type error.

any type must be explicitly cast to be used in expressions:

let x: any = 1;
let d = 100 + x as int; // omitting cast would produce an error

Union types

Types can be composed to form a union. Works similarly to Typescript's Union Types.

let mut x: str|nil = nil;
x = "string";

fn triple(n: int|float) -> int|float {
    return n * 3;
}

triple(2);
triple(2.2);

struct Foo { 
    bar: str|int
}

Type aliases

Type aliases can be created with a type declaration statement.

type Celcius = int;

// works with union types as well
type IntStrVec = vec<int>|vec<str>;

Type alias behaves like a normal type and can be used wherever a type is expecte.

Control Flow and Loops

Parentheses are not needed around conditions. The statement body must be enclosed in curly braces.

If

if statement is rather classic. It supports else if and else branches.

if x >= 100 {
    println("x is more than 100");
} else if x <= 100 && x > 0 {
    println("x is less than 100, but positive");
} else {
    println("x a non-positive number");
}

Match

match expression returns the first matching arm evaluated value.

Unlike other control flow statements, match is an expression and therefore must be terminated with a semicolon.

let direction = match get_direction() {
    "north" => 0,
    "east" => 90,
    "south" => 180,
    "west" => 270,
};

match true can be used to make more generalised comparisons.

let age = 40;

let description: str = match true {
    age > 19 => "adult",
    age >= 13 && x <= 19 => "teenager",
    age < 13 => "kid",
};

match can be used with enums

enum HttpStatus {
    NotFound,
    NotModified,
    Ok
}

type Code = int;

impl HttpStatus {
    fn code(status: Self) -> Code {
        return match status {
            Self::NotFound => 404,
            Self::NotModified => 304,
            Self::Ok => 200,
        };
    }
}

fn main() {
    let status: Code = HttpStatus::code(HttpStatus::Ok); // 200
}

While

There are three loops in Oxide: while, loop and for.

Loops support break and continue statements.

while statement is rather usual.

while x != 100 {
    x += 1;
}

Loop

loop looks like Rust's loop. Basically it is while true {} with some nice looking syntax.

loop {
    x.push(0);
    if x.len() > 100 {
        break;
    }
}

For

for in loops are used to iterate over a vector.

for x in 0..=100 {
    println(x);
}

or with an index:

for pos, name in vec["John", "Johann", "Jane"] {
    println(pos as str + ": " + name); // 0: "John" ...
}

There is also a good old C-like for loop.

for let mut i = 0; i < v.len(); i += 1 {
    println(v[i] as str);
}

Like in C, the first or the last parts can be omitted, or even all three of them for ;; {}.

Functions

Functions are declared with a fn keyword.

Function signature must explicitly list all argument types as well as a return type.

Functions that do not have a return statement implicitly return nil and the -> nil may be omitted.

Each function is of fn(T) -> T type.

fn add(x: int, y: int) -> int {  // typeof(add) = fn(int, int) -> int
    return x + y;
}

fn clone(c: Circle) -> Circle {  // typeof(clone) = fn(Circle) -> Circle
    return Circle {
        radius: c.radius,
        center: c.center,
    };
}

fn log(level: int, msg: str) {   // typeof(log) = fn(int, str) 
    println(
      "Level: " + level as str + ", message: " + msg
    );
}

Defining a function argument as mut lets you mutate it in the function body. By default, it is immutable.

/// compute the greatest common divisor 
/// of two integers using Euclids algorithm
fn gcd(mut n: int, mut m: int) -> int {   // typeof(gcd) = fn(int, int) -> int
    while m != 0 {
        if m < n {
          let t = m;
          m = n;
          n = t;
        }
        m = m % n;
    }
  
    return n;
}

gcd(15, 5); // 5

Closures

Functions are first-class citizens of the language, they can be stored in a variable of type fn(T) -> T, passed to or/and returned from another function.

/// function returns closure
/// which captures the internal value i
/// each call to the closure increments the captured value
fn create_counter() -> fn() {       // typeof(create_counter) = fn() -> fn()
    let mut i = 0;

    return fn () {                  // returns closure
        i += 1;
        println(i as str);
    };
}

let counter = create_counter();     // type is inferred as fn() -> fn()

counter(); // 1
counter(); // 2
counter(); // 3

Functions can be passed by their name directly

fn str_concat(a: str, b: str) -> str {
    return a + b;
}

fn str_transform(
    callable: fn(str, str) -> str, 
    a: str,
    b: str
) -> str {
    return callable(a, b);
}

str_transform(str_concat, "hello", " world");

Immediately Invoked Function Expressions, short IIFE, are also supported for whatever reason.

(fn (names: vec<str>) {
    for pos, name in names {
        println(pos as str + ": " + name);
    }
})(vec["Rob", "Sansa", "Arya", "Jon"]); 

// 0: Rob
// 1: Sansa
// ...

Structs

Structs represent the user-defined types. Struct declaration starts with struct keyword. All struct properties are mutable by default.

You can make property public with a pub keyword. Public fields can be accessed from outer scope.

struct StellarSystem {           
    pub name: str|nil,           // public field
    pub planets: vec<Planet>,    // public vector of structs
    pub star: Star,         
    age: int                     // private field
}

struct Star { 
    pub name: str,
    mass: int,                  
}

struct Planet {
    pub name: str,
    mass: int,
    belt: bool,
}

Struct implementation starts with impl keyword. While struct declaration defines its properties, struct implementation defines its methods, static methods and constants.

• self keyword can be used inside methods and points to the current struct instance. i.e self.field
• Self (capitalised) keyword can be used inside methods to point to the current struct name, i.e. Self::CONSTANT or Self::static_method(x), it can be used as a type as well let p: Self = Self { .. };

You can make methods and constants public with a pub keyword. Public methods and constants can be accessed from outer scope.

Methods with self as the first argument are instance methods. Methods without it are static methods.

impl Star {                      
    pub const WHITE_DWARF: float = 123.3;       // public associated constants
    pub const NEUTRON_STAR: float = 335.2;      // lets pretend those values are real
    pub const BLACK_HOLE: float = 9349.02;  
  
    const MAX_AGE: int = 99999;                 // private constant
  
    pub fn new(name: str, mass: int) -> Self {  // public static method
        return Self {
            name: name,
            mass: mass,
        };
    }
    
    pub fn get_description(self) -> str {  // public instance method
        return match true {
            self.mass <= Self::WHITE_DWARF => "white dwarf",
            self.mass > Self::WHITE_DWARF && self.mass <= Self::BLACK_HOLE => "neutron star",
            self.mass >= Self::BLACK_HOLE => "black hole",
        };
    }
}

impl Planet {
    pub fn set_new_mass(self, mass: int) {
        self.mass = mass;
    }

    fn is_heavier(self, p: Self) -> bool {      // private method
        return self.mass > p.mass;
    }
}

You need to initialize all structs properties on instantiation.

let planet_mars: Planet = Planet {                   
    name: "Mars",
    mass: 100,
    belt: false,
};

let system = StellarSystem {
    name: "Solar System",
    star: Star { name: "Sun", mass: 9999 },
    planets: vec[
        planet_mars,                                        // via variable
        Planet { name: "Earth", belt: false, mass: 120 }    // via inlined struct instantiation
    ],    
    age: 8934,
};

let arcturus = Planet::new("Arcturus", 4444);               // creating instance via static method

Dot syntax . is used to access structs fields and call its methods.

// set new value
system.name = "new name";
system.planets.push( Planet {
    name: "Venus",
    belt: false,
    mass: 90,
});

// get value
let mars_name: str = system.planets[0].name;

// call method
let desc: str = system.star.get_description();
system.planets[0].set_new_mass(200);

:: is used to access constants and static methods:

impl Star {
    pub const WHITE_DWARF: float = 123.3;
    const MAX_AGE: int = 99999; 
    
    // inside methods Self:: can be used instead
    pub fn get_max_age() -> int {
        return Self::MAX_AGE;
    }
}

let dwarf_mass: int = Star::WHITE_DWARF;
let max_age: int = Star::get_max_age();

Same as in Rust, non-static methods can be called using :: as well:

let desc = Star::get_description(system.star);
// same as
let desc = system.star.get_description();

Immutable variable behave similarly to Javascript const that holds an object, so it will still let you change the object fields.

system.name = "new name";              // valid
system.planets[0].name = "new name";   // also valid
system = StellarSystem { ... };        //! error, "system" cannot point to another struct

Structs are always passed by reference, consider:

fn rename_system(s: StellarSystem) {
    s.name = "new name";
}

rename_system(system);

println(system.name); // "new name"

Public and Private

Only public properties, methods and constants can be accessed from outer code.

system.age = 100;                //! access error, "age" is private
system.planets[0].mass;          //! access error, "mass" is private
system.planets[0].is_heavier(p); //! access error, "is_heavier()" is private
Star::MAX_AGE;                   //! access error, "Star::MAX_AGE" is private

Traits

Traits are similar to Rust traits and are used to define shared behavior.

Because all trait methods are always public they are defined with no pub keyword.

trait Shape {
    fn calc_area(self) -> float;
  
    fn calc_perimeter(self) -> float;
}

Trait body lists function signatures that must be implemented when implementing the trait:

impl Shape for RightTriangle {
    fn calc_area(self) -> float {
        return self.a * self.b / 2;
    }
  
    fn calc_perimeter(self) -> float {
        return self.a + self.b + self.c;
    }
}

impl Shape for Rectangle {
    fn calc_area(self) -> float {
        return self.a * self.b;
    }
  
    fn calc_perimeter(self) -> float {
        return (self.a + self.b) * 2;
    }
}

All structs that implement the Shape trait can be used wherever a shape is expected:

fn print_shape_values(shape: Shape) {
    let area = shape.calc_area();
    let perimeter = shape.calc_perimeter();

    println("The area is " + area as str);
    println("The perimeter is " + perimeter as str);
}

let a = Rectangle::new(10, 30);
print_shape_values(a); 

Enums

Same as structs, enums represent user-defined types. Enums are quite simple and similar to C-style enums.

enum TimeUnit {
    Seconds,
    Minutes,
    Hours,
    Days,
    Months,
    Years,
}

let days = TimeUnit::Days; // inferred type as "TimeUnit"

impl blocks can be used to implement static methods and constants on enums.

impl TimeUnit {   
    pub fn plural(time: Self) -> str {
        return match time {
            Self::Seconds => "seconds",
            Self::Minutes => "minutes",
            Self::Hours => "hours",
            Self::Days => "days",
            Self::Months => "months",
            Self::Years => "years"
        };
    }
}

TimeUnit::plural(days); // "days"

Equality of enum values can be checked with == and != or with match

days == TimeUnit::Days;             // true
TimeUnit::Years == TimeUnit::Hours; // false

Different types of enum values are not compatible and comparing them will trigger an error

enum Ordering {
    Less,
    Equal,
    Greater
}

Ordering::Less == TimeUnit::Days; //! type error

Vectors

Vectors, values of type vec<T>, represent arrays of values and can be created using vec[] syntax, where T is any Oxide type.

Vectors have built-in methods:

• vec.push(val: T) push value to the end of the vector
• vec.pop() -> T remove value from the end of the vector and return it
• vec.len() -> int get vectors length

let planets = vec["Mercury", "Venus", "Earth", "Mars"];

planents.push("Jupiter");    // "Jupiter" is now the last value in a vector
let jupiter = planets.pop(); // "Jupiter" is no longer in a vector.

let mars = planets[3];       // mars = "Mars"
planets[2] = "Uranus";       // "Earth" is gone. "Uranus" is on its place now

planets.len();               // 3

typeof(planets);             // vec<str>

Variables can be either declared with the type

let v: vec<int> = 0..10;    // typeof(v) = vec<int>
let v: vec<Dog>;            // typeof(v) = vec<Dog>

or it can be inferred if the type is omitted:

let v = vec[true, false];    // typeof(v) = vec<bool>

let v = vec[                 // typeof(v) = vec<Dog>
    Dog { name: "dog1" },
    Dog { name: "dog2" },
];

let v = vec[                 // typeof(v) = vec<vec<Point>,
    vec[                                
        Point { x: 1, y: 1 }, 
        Point { x: 0, y: 3 } 
    ],
    vec[ 
        Point { x: 5, y: 2 }, 
        Point { x: 3, y: 4 } 
    ],
];


let matrix = vec[            // typeof(v) = vec<vec<int>>
    vec[1, 2, 3, 4, 5],
    0..=5,
    0..6,
];

let things = vec[            // typeof(v) = vec<any>
    Ordering::Less,
    false,
    Point {}
];   

Like structs, vectors are passed by reference.

Consider this example of an in place sorting algorithm, selection sort, that accepts a vector and sorts it in place, without allocating memory for a new one.

fn selection_sort(input: vec<int>) {
    if input.len() == 0 { return; }

    let mut min: int;
    for i in 0..(input.len() - 1) {
        min = i;

        for j in i..input.len() {
            if input[j] < input[min] {
                min = j;
            }
        }

        if min != i {
            let temp = input[i];
            input[i] = input[min];
            input[min] = temp;
        }
    }
}

Range Expressions

The .. and ..= operators will construct a vec<int> and fill it will the sequential integers.

let x = 0..=5;  // typeof(x) = vec<int>, [0, 2, 3, 4, 5]
let x = 0..5;   // typeof(x) = vec<int>, [0, 2, 3, 4]

Ranges can be used in for in loops:

for x in 1..15 {
    println(x as str);
}

Constants

Constants are top-level instructions like fn, trait, struct, impl. Redeclaring a constant results in a runtime error. Constants must hold only a scalar value: str, int, float, bool.

const SOME_THRESHOLD = 100;

const EPSILON = 0.004;

const MESSAGE: str = "hello world";

Struct implementations (impl blocks) can also define constants. Those constants can be either public or private.

struct Math {}

impl Math {
    pub const PI = 3.14159265;  // public const
    const E = 2.71828182846;    // private const
  
    pub fn get_e() -> float {
        return Self::E;         // Self:: is the same as Math:: inside methods
    }
}

Accessing private consts from outer scope will result in an error.

let pi = Math::PI;     // ok
let e = Math::E;       //! access error
let e = Math::get_e(); // ok

Operators

Unary

• ! negates boolean value
• - negates number

Binary

• &&, || logic, operate on bool values
• <, >, <=, >=, comparison, operate on int, float values
• ==, != equality, operate on values of the same type
• -, /, +, *, % math operations on on int, float values
• &, |, ^ bitwise operations on integers
• + string concatenation
• as type cast operator, used to convert primitives to some type: 30 as bool
• .., ..= range operators, create a vec<int> value
• =, +=, -=, /=, %=, *=, &=, |=, ^= various corresponding assignment operators

Comments

Classic comments that exist in most other C-like languages.

// inline comments

/*
    multiline comment
 */

let x = 100; /* inlined multiline comment */ let y = x;

Standard library

A small set of built-in functionality is available anywhere in the code.

• typeof(val: any) -> str returns type of given value or variable
• args() -> vec<str> returns an array of arguments passed to script
• dbg(val: any) dumps val as a string to the standard output stream (stdout).
• print(msg: str) prints msg to the stdout.
• println(msg: str) same as print, but inserts a newline at the end of the string.
• eprint(err: str) prints err to the standard error (stderr).
• eprintln(err: str) you got the idea.
• timestamp() -> int returns current Unix Epoch timestamp in seconds
• read_line() -> str reads user input from standard input (stdin) and returns it as a str
• file_write(file: str, content: str) -> str write content to a file, creating it first, should it not exist