ST Language

An interpreted language with a JavaScript-like syntax, written in Typescript. It features a lexer, ast, parser, interpreter, REPL and file runner.

Table of Contents

• Syntax and Features
  • Data Types
  • Expressions
    • Unary
    • Binary
    • Assignment
    • Member Access
      • Computed
      • Object With Identifier
      • Type Specific Built-in Properties
    • Function Call
  • Statements
    • Variable Declaration
    • Control Flow
      • If-Else
      • For Loop
      • While Loop
    • Function Declaration
  • Comments
  • Native Functions
• Installation
• Available Scripts
• Usage
• Roadmap
• Contributing
• License
• Acknowledgements

Syntax and Features

Data Types

• Number 3, 3.14
• String "Hello, World!"
• Boolean true, false
• Null null
• Array [1, 2, 3]
• Object { key: "value" }

Expressions

Unary

• Logical !
• Negation -
• Positive +

Binary

• Multiplicative (*, /, //, %)
• Additive (+, -)
• Relational (==, !=, <, <=, >, >=)
• Logical (&&, ||)

Assignment

x = 3

Member Access

Computed

foo[0]
foo[3 + 4]
foo["bar"]

Object With Identifier

foo.bar

Type Specific Built-in Properties

const foo = []

foo.length
foo.push(3)

Function Call

add(3, 4)

Statements

Variable Declaration

const PI = 3
let bar = "Hello, World!"

Control Flow

If-Else

limited to if-else for now, parentheses are optional

if 3 > 2 {
  print("3 is greater than 2")
} else {
  print("foo")
}

For Loop

for let i = 0; i < 10; i = i + 1 {
  print(i)
}

While Loop

let i = 0

while i < 10 {
  print(i)
  i = i + 1
}

Function Declaration

Function declarations support both closures and recursion.

fn fib(n) {
  if n <= 1 {
    return n
  }

  return fib(n - 1) + fib(n - 2)
}

Comments

# this is a comment

Native Functions

print("Hello, World!")
const name = input("What is your name?")
random()
random(1, 10)
typeof(3)

Installation

Ensure you have Bun (v1.1.x or higher) installed.

bun install

Available Scripts

Command	Description
bun lint	Lint
bun test	Test
bun run repl	Run the REPL
bun file <file>	Run a file

Usage

Example file program.st:

fn add(a, b) {
  let sum = a + b
  return sum
}

let result = add(3, 4)

const foo = {
  result: result / 3,
  add,
  isBar: 1 > 2 || 3 < 4,
}

if foo["is" + "Bar"] {
  print("foo is bar")
} else {
  print("foo is not bar")
}

print(foo.result)
print(foo.add(3, 4))

for let i = 0; i < 10; i = i + 1 {
  print(i)
}

fn counter() {
  let count = 0
  fn increment() {
    count = count + 1
    return count
  }
  return increment
}

const increment = counter()

while increment() < 10 {
  print(increment())
}

Run file: bun file program.st

Roadmap

• Control Flow (elif)
• Update expressions (++, --) postfix/prefix and (+=, -=, ...)
• Error handling (try-catch, throw)
• Better error messages with line numbers, context, etc.
• OOP
• Types
• Standard library
• Modules
• Improve REPL, add history, autocomplete, etc.
• Syntax highlighting (VSCode extension)
• Rewrite in Rust

Contributing

1. Fork the project
2. Create your feature branch (git checkout -b fix/tokenizer-number-parsing)
3. Commit your changes (git commit -m 'fix: parsing numbers')
4. Push to the branch (git push origin fix/tokenizer)
5. Open a PR

License

Distributed under the MIT License. See LICENSE for more information.

Acknowledgements

• https://www.youtube.com/playlist?list=PL_2VhOvlMk4UHGqYCLWc6GO8FaPl8fQTh
• https://astexplorer.net/