Cobain

A compiler for a custom programming language, built from scratch in Swift with an LLVM backend. Developed as a bachelor's diploma project to demonstrate the full compilation pipeline: lexical analysis, parsing, and native code generation.

The Language

Cobain is a small, expression-oriented language with a functional flavor. Functions are defined with the motif keyword, and conditionals use an is ... ? ... : ... ternary syntax.

# Factorial function
motif fact(a) {
    is a < 1 ? a : a * fact(a - 1)
}
print(fact(5))

Language Features

• Functions defined with motif
• External declarations with extern
• Binary operators: +, -, *, /, <, >
• Conditional expressions: is condition ? then : else
• Recursive function calls
• Comments with #

Architecture

The compiler follows the classic three-stage pipeline:

Source Code → Lexer → Parser → LLVM Code Generator → Native Bitcode

Stage	Description
Lexer	Tokenizes source into keywords, identifiers, numbers, and operators using a generic Stream<T> abstraction
Parser	Recursive descent parser with operator precedence climbing, producing an AST enum
Code Generator	Translates the AST to LLVM IR via the LLVM-C API, then emits bitcode (result.bc)

Project Structure

Cobain/
├── Cobain/                  # CLI entry point
│   └── main.swift
├── CobainFramework/         # Core compiler library
│   ├── Lexer/               # Tokenizer (Lexer, Token, Stream)
│   ├── Parser/              # AST & recursive descent parser
│   ├── Codegen/             # LLVM IR generation
│   ├── Stdlib/              # Built-in functions (print, printf)
│   └── Extensions/          # Swift helper extensions
├── CobainTests/             # XCTest unit tests
└── LLVM/                    # Pre-built LLVM 3.8 static libraries & headers

Building

Requires Xcode. The repository includes pre-built LLVM static libraries, so no separate LLVM installation is needed.

# Open in Xcode
open Cobain.xcodeproj

# Or build from command line
xcodebuild -project Cobain.xcodeproj -target Cobain

Usage

# Run the default example (factorial)
./Cobain

# Compile a source file
./Cobain program.cb

# Inspect compiler stages
./Cobain -emit-tokens program.cb   # Show lexer output
./Cobain -emit-ast program.cb      # Show parsed AST
./Cobain -emit-llvm program.cb     # Show generated LLVM IR

Tech Stack

• Swift — compiler implementation
• LLVM 3.8 C API — backend code generation
• XCTest — unit testing
• Xcode — build system

License

This project was developed as a bachelor's thesis. All rights reserved.