Voyd

Voyd is a high performance WebAssembly language with an emphasis on full stack web development.

fn fib(n: i32) -> i32
  if n < 2 then:
    n
  else:
    fib(n - 1) + fib(n - 2)

pub fn main()
  fib(10)

Disclaimer

Voyd is in it's very early stages of development. Voyd is not ready for production use. Some syntax and semantics are still subject to change. Expect frequent breaking changes.

All features documented in README Overview are fully implemented unless otherwise stated. Features documented in the reference are not yet marked with status and may not be implemented.

Features:

• Functional
• Hybrid Nominal & Structural type system
• Algebraic effects
• First class wasm support
• Macros and language extensions
• Uniform function call syntax

Guiding Principles:

• Fun to write and read.
• Predictability
• Hackability
• Balance a great developer experience with performance
• Play nice with others

Getting Started

Install

npm i -g voyd

Usage Examples

# Run the exported main function
voyd --run script.voyd

# Compile a directory (containing an index.voyd) to webassembly
voyd --emit-wasm src > output.wasm

# Compile to optimized WebAssembly
voyd --emit-wasm --opt src > output.wasm

Requirements

Currently requires node v22

# Or nvm
fnm install v22

Overview

Quick overview of the language. More detailed reference available here

Comments

// Comments are single line and are marked with a c style slash slash

Primitive Types

true // Boolean
false // Boolean
1 // i32 by default
1.0 // f64 by default
"Hello!" // String literal, can be multiline, supports interpolation via ${} (NOTE: Interpolation not yet implemented)
[1, 2, 3] // Array literal. (NOTE: Not yet implemented. Arrays can be initialized with new_array<T>({ from: FixedArray(val1, val2, etc) })
(1, 2, 3) // Tuple literal  (NOTE: Not yet implemented)
{x: 2, y: 4} // Structural object literal

Variables

// Immutable variable
let my_immutable_var = 7

// Mutable variable
var my_var = 7

Functions

A Basic function:

fn add(a: i32, b: i32) -> i32
  a + b

In most cases the return type can be inferred

fn add(a:i32, b:i32)
  a + h

To call a function, use the function name followed by the arguments in parenthesis

add(1, 2)

Voyd also supports uniform function call syntax (UFCS), allowing functions to be called on a type as if they were methods of that type.

1.add(2)

Labeled arguments

Status: Not yet implemented

Labeled arguments can be defined by wrapping parameters you wish to be labeled on call in curly braces.

fn add(a: i32, {to: i32}) = a + to

add(1, to: 2)

By default, the argument label is the same as the parameter name. You can override this by specifying the label before the argument name.

fn add(a: i32, {to:b: i32}) = a + b

add(1, to: 2)

Labeled arguments can be thought of as syntactic sugar for defining a object type parameter and destructuring it in the function body[1]:

fn move({ x: i32 y: i32 z: i32 }) -> void
  // ...

// Semantically equivalent to:
fn move(vec: { x: i32 y: i32 z: i32 }) -> void
  let { x, y, z } = vec
  // ...

move(x: 1, y: 2, z: 3)

// Equivalent to:
move({ x: 1, y: 2, z: 3 })

This allows you to still use object literal syntax for labeled arguments when it might be cleaner to do so. For example, when the variable names match the argument labels:

let (x, y, z) = (1, 2, 3)

// Object field shorthand allows for this:
move({ x, y, z })

// Which is better than
move(x: x, y: y, z: z)

[1] The compiler will typically optimize this away, so there is no performance penalty for using labeled arguments.

If Expressions

if 3 < val then:
  "hello" // true case
else:
  "bye" // false case (optional)

Ifs are expressions that return a value

let x = if 3 < val then: "hello" else: "bye"

Loops

Status: Partially implemented.

• Tail call optimization fully implemented.
• While loops and break partially implemented. Do not yet support returning a value.
• For loops not yet implemented.

While loops are the most basic looping construct

while condition do:
  do_work()

For loops can iterate through items of an iterable (such as an array)

for item in iterable do:
  print item

Voyd is also tail call optimized:

// This function is super speedy and uses very little memory
pub fn fib(n: i32, a: i32, b: i32) -> i32
  if n < 1 then: a
  else: fib(n - 1, b, a + b)

pub fn main() -> i32
  fib(10, 0, 1)

Structural Objects

Structural objects are types compatible with any other type containing at least the same fields as the structure.

fn get_x(obj: { x: i32 })
  obj.x

pub fn main()
  let vec = {
    x: 1,
    y: 2,
    z: 3
  }

  vec.get_x() // 1

Nominal Objects

Nominal objects attach a name (or brand) to a structure, and are only compatible with extensions of themselves.

obj Animal {
  age: i32
}

obj Cat extends Animal {
  age: i32,
  lives: i32
}

obj Dog extends Animal {
  age: i32,
  borks: i32
}

fn get_age(animal: Animal)
  animal.age

pub fn main()
  let dog = Dog { age: 3, borks: 0 }
  dog.get_age() // 3
  let person = { age: 32 }
  person.get_age() // Error { age: 32 } is not a type of animal

Methods

obj Animal {
  age: i32
}

impl Animal
  pub fn get_age(animal: Animal)
    animal.age

Intersections

Intersections combine a nominal type and a structural type to define a new type compatible with any subtype of the nominal type that also has the fields of the structural type.

obj Animal { age: i32 }
obj Snake extends Animal {}
obj Mammal extends Animal { legs: i32 }

type Walker = Animal & { legs: i32 }

fn get_legs(walker: Walker)
  walker.legs

pub fn main()
  let dog = Mammal { age: 2, legs: 4 }
  dog.get_legs

Unions

Unions define a type that can be one of a group of types

obj Apple {}
obj Lime {}
obj Orange {}

type Produce = Apple | Lime | Orange

Match Statements

Match statements are used for type narrowing

obj Animal
obj Cat extends Animal
obj Dog extends Animal

let dog = Dog {}

match(dog)
  Dog: print "Woof"
  Cat: print "Meow"
  else:
    print "Blurb"

Match statements must be exhaustive. When matching against a nominal object, they must have an else (default) condition. When matching against a union, they must have a case for each object in the union

Traits

Status: Partially implemented Supported for nominal types. Trait scoping is not yet enforced.

Traits define a set of behavior that can be implemented on any nominal object or intersection.

trait Walk
  fn walk() -> i32

// Implement walk for any animal that contains the field legs: i32
impl Walk for Animal & { legs: i32 }
  fn walk(self)
    self.walk

// Traits are first class types
fn call_walk(walker: Walk)
  walker.walk

fn do_work(o: Object)
  // Traits also have runtime types
  if (o has_trait Walk) then:
    o.call_walk()

Closures

Status: Not yet implemented

let double = n => n * 2

array.map n => n * 2

Voyd also supports a concise syntax for passing closures to labeled arguments:

try do():
  call_fn_that_has_exception_effect()
catch:
  print "Error!"

Dot Notation

The dot is a simple form of syntactic sugar

let x = 4

x.squared

// Translates to
squared(x)

Generics

Status: Basic implementation complete for objects, functions, impls, and type aliases. Inference is not yet supported.

fn add<T>(a: T, b: T) -> T
  a + b

With trait constraints

fn add<T: Numeric>(a: T, b: T) -> T
  a + b

Effects

Status: Not yet implemented

Effects (will be) a powerful construct of the voyd type system. Effects are useful for a large class of problems including type safe exceptions, dependency injection, test mocking and much more.

Think of libraries like TypeScript's Effect library, built directly into the language.

effect Exception
  // An effect that may be resumed by the handler
  ctl throw(msg: String) -> void

// Effects with one control can be defined concisely as
effect ctl throw(msg: String) -> void

effect State
  // Tail resumptive effect, guaranteed to resume exactly once.
  // Are defined like normal functions
  fn get() -> Int
  fn set(x: Int) -> void

// Tail resumptive effects with one function can be defined more concisely as
effect fn get() -> Int

JSX

Status: Implementation in progress

Voyd has built in support for JSX. Useful for rendering websites or creating interactive web apps

fn app() -> JSX::Element
  let todo_items = ["wake up", "eat", "code", "sleep"]
  <div>
    <h1>TODO</h1>
    <ul>
      {todo_items.map i => <li>{i}</li>}
    </ul>
  </div>