drag-rs

Overview

drag-rs is a lightweight programming language compiler written in Rust. It parses source code and generates LLVM IR using the inkwell crate. Currently, it supports parsing simple strongly-typed function definitions, arithmetic operations, and external functions.

Features

• **Lexer & Parser:** Hand-rolled recursive descent parser building a strongly-typed AST.
• **LLVM CodeGen:** Translates the parsed AST into optimized LLVM IR.
• **Strong Typing:** Predictable type semantics, currently utilizing f64 as the primitive base type.
• **Arithmetic Operations:** First-class support for +, -, *, /, and <.
• **Extern Signatures:** Ability to declare external functions for FFI (e.g., C math functions).
• **Command Line Interface:** Easy testing with simple string-based inputs or file read support.

Syntax Example

A standard function definition requires the fn keyword, explicitly typed arguments, a return type, and curly braces:

fn add_one(x: f64) -> f64 {
    1 + x
}

You can also declare external C functions to call from within your code:

extern sin(x: f64) -> f64

Usage

First, build the compiler using cargo (make sure you have the respective LLVM development packages installed on your system for inkwell):

cargo build

Compile via String

Provide a quick snippet to generate IR. By default, the output is saved to output.ll.

cargo run -- -i "fn test(x: f64) -> f64 { 1 + x }"

Compile via File

Pass a source file to be parsed and compiled. You can also specify a custom output path for the LLVM IR.

cargo run -- -f example.drag -o generated.ll

Roadmap

This language is an evolving technical playground for compiler structure. Upcoming milestones could include:

• [ ] Control Flow (if / else, for / while loops)
• [ ] Native executable creation from LLVM IR (object files and linking)
• [ ] Variable assignment (let / mut)
• [ ] Extended types (integers, booleans, strings) and type checking

• [ ] Top-level expression execution (REPL-style evaluation for immediate feedback)
• [ ] Add control flow support (if / else)
• [ ] Add local variables and assignment (let, =)
• [ ] Parse multiple definitions per file and generate a callable entry main
• [ ] Add user-selectable optimization levels (-O0 / -O1 / -O2 / -O3)
• [ ] Add parser/codegen tests (including golden IR tests)