LittleSwift

A simple self-hosted Swift compiler

LittleSwift is a simple compiler written in Swift that can compile Swift code. It's simply a project I've been working on to gain further understanding about compilers and it's not meant to replace the real Swift compiler any time soon.

Note: It's a basic compiler at the moment and it's not meant for production use!

Features

What can it do?

• Tokenize, Parse, Sema, IRGen, Output Binary
• Supports a strict subset of Swift grammar
  • Functions and variables
  • Primitive types (String, Int, Float, Void, Bool)
  • Binary operators (+, -, *, /)
  • print
• Just-in-time (JIT) compilation
• Interpreter (REPL)
• Emit Kotlin code
• Basic type inference

What it can't do?

• Support classes, protocols, generics, etc
• Support other types like Array and List
• Module maps
• Optimizations
• Many more things...

Example

func main() {
    print("Hello! This program prints the square root of 5.")
    
    let numberToSquare = 5
    let answer = square(numberToSquare)
    
    print("The square root of 5 is: ")
    print(answer)
}

func square(number: Int) -> Int {
    return multiply(number, number)
}

func multiply(first: Int, second: Int) -> Int {
    return first * second
}

// Output:
//
// Hello! This program prints the square root of 5.
// The square root of 5 is:
// 25

Installation

1. Install LLVM 6 (brew install llvm@6)
2. Install the LLVM pkg-config file (swift utils/make-pkgconfig.swift)
3. Run swift package resolve and then swift package generate-xcodeproj.

Usage

Refer to the command-line parameters. You can simply invoke the compiler without any arguments and it will print all the parameters it supports.

License

LittleSwift

Copyright (C) 2018 Suyash Srijan

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.