Ruchy

A systems scripting language that transpiles to idiomatic Rust, combining Python-like ergonomics with zero-cost execution and compile-time verification.

// Ruchy - expressive, safe, performant
#[property]
fun fibonacci(n: i32) -> i32 {
    match n {
        0 | 1 => n,
        _ => fibonacci(n - 1) + fibonacci(n - 2)
    }
}

// Actor-based concurrency
actor Calculator {
    state: f64 = 0.0,
    
    receive {
        Add(value) => self.state += value,
        Multiply(value) => self.state *= value,
        GetResult(reply) => reply.send(self.state)
    }
}

// DataFrame operations with method chaining
fun analyze_data(df: DataFrame) -> DataFrame {
    df.filter(col("score") > 90)
      .groupby("category") 
      .agg([
          col("value").mean().alias("avg"),
          col("value").std().alias("stddev")
      ])
}

Current Implementation Status (v0.2.1)

🎉 New in v0.2.1

• REPL State Persistence: Functions and definitions persist across REPL commands
• Enhanced String Interpolation: Full AST support for "Hello, {expr}!" syntax
• Grammar Coverage Testing: Comprehensive testing of all language constructs
• Property-Based Testing: Robust fuzzing and property testing framework
• Zero Technical Debt: Complete elimination of TODO/FIXME comments

✅ Completed Features

Core Language

• Parser: Recursive descent with Pratt parsing for operators
• Type System: Hindley-Milner inference with Algorithm W
• Transpilation: AST to idiomatic Rust code generation
• REPL: Interactive development with error recovery
• Pattern Matching: Match expressions with guards
• Pipeline Operators: |> for functional composition

Modern Language Features

• Async/Await: First-class asynchronous programming
• Actor System: Concurrent programming with ! (send) and ? (ask) operators
• Try/Catch: Exception-style error handling transpiled to Result
• Property Testing: #[property] attributes generating proptest code
• Loop Control: break and continue statements

Data Processing

• DataFrame Support: Polars integration with filtering, grouping, aggregation
• Vec Extensions: sorted(), sum(), reversed(), unique(), min(), max()
• String Interpolation: "Hello {name}" syntax

Developer Experience

• Error Recovery: Robust parser with helpful error messages
• Type Inference: Bidirectional checking with local inference
• Method Calls: Object-oriented syntax obj.method(args)
• Lambda Expressions: |x| x + 1 syntax

🔧 Technical Achievements

• 227 Passing Tests with comprehensive test coverage
• 78.25% Code Coverage exceeding 75% requirement
• Zero SATD Policy: No TODO/FIXME/HACK comments in codebase
• Performance: Type inference <5ms per 1000 LOC
• Quality Gates: All linting and complexity requirements met
• REPL Reliability: State persistence across commands with crash recovery

Getting Started

Installation

# Clone and build
git clone https://github.com/paiml/ruchy
cd ruchy
cargo build --release

# Run the REPL
cargo run -p ruchy-cli -- repl

# Transpile a file
cargo run -p ruchy-cli -- transpile examples/hello.ruchy

Quick Examples

Basic Function with Type Inference

fun greet(name) {
    "Hello, {name}!"
}

Async Programming

async fun fetch_data(url: String) -> Result<String> {
    let response = http_get(url).await?;
    response.text().await
}

Actor Concurrency

actor Counter {
    count: i32 = 0,
    
    receive {
        Increment => self.count += 1,
        GetCount(reply) => reply.send(self.count)
    }
}

fun main() {
    let counter = spawn!(Counter);
    counter ! Increment;
    let result = counter ? GetCount;
}

Property-Based Testing

#[property]
fun test_addition_commutative(a: i32, b: i32) {
    assert_eq!(a + b, b + a);
}

Usage

Command Line Interface

The Ruchy CLI provides several commands for working with Ruchy code:

# Start interactive REPL
ruchy repl

# Transpile a single file
ruchy transpile examples/hello.ruchy

# Transpile and run
ruchy run examples/fibonacci.ruchy

# Type check without generating code
ruchy check src/main.ruchy

# Show AST for debugging
ruchy ast examples/test.ruchy

# Display help
ruchy --help

REPL Commands

The interactive REPL supports special commands:

// Show compiled Rust code
:rust 1 + 2

// Display AST
:ast let x = 42

// Show inferred type  
:type fibonacci

// Clear session
:clear

// Show command history
:history

// Exit REPL
:quit

Programmatic API

use ruchy::{compile, is_valid_syntax, get_parse_error};

// Compile Ruchy code to Rust
let rust_code = compile("fun add(a, b) { a + b }")?;

// Validate syntax
assert!(is_valid_syntax("let x = 42"));

// Get detailed error information
if let Some(error) = get_parse_error("let x = ") {
    println!("Parse error: {}", error);
}

Architecture

┌─────────────┐    ┌──────────────┐    ┌─────────────────┐    ┌──────────────┐
│   .ruchy    │───▶│    Parser    │───▶│ Type Inference  │───▶│  Transpiler  │
│   Source    │    │ (Recursive   │    │  (Algorithm W)  │    │  (Rust AST)  │
│             │    │  Descent)    │    │                 │    │              │
└─────────────┘    └──────────────┘    └─────────────────┘    └──────┬───────┘
                                                                      │
┌─────────────┐    ┌──────────────┐                                   │
│    REPL     │◀───│ Interpreter  │                                   │
│ (Terminal)  │    │ (Tree-walk)  │                                   │
└─────────────┘    └──────────────┘                                   ▼
                                                              ┌──────────────┐
                                                              │     rustc    │
                                                              │  (Native)    │
                                                              └──────────────┘

Language Features

Type System

• Hindley-Milner type inference with Algorithm W
• Gradual typing - optional type annotations
• Bidirectional checking for local inference
• Polymorphic functions with automatic generalization

Concurrency

• Actor model with message passing via ! and ?
• Async/await for structured concurrency
• Supervisor trees for fault tolerance

Data Processing

• DataFrame operations with Polars backend
• Pipeline operators for functional composition
• Method chaining for fluent APIs
• Vector extensions for common operations

Quality Assurance

• Property testing with automatic test generation
• Pattern matching with exhaustiveness checking
• Error handling via Result types and try/catch
• Zero-cost abstractions - compiles to optimal Rust

Development Status

🎯 Next Priorities (v0.3)

1. List Comprehensions - [x for x in list if condition]
2. Generic Type Parameters - <T> syntax for functions
3. Object Literals - { key: value } syntax
4. Enhanced Module System - Complete import/export resolution

🔮 Future Features (v1.0)

• Binary Architecture - Single binary with integrated toolchain
• Cargo Integration - Seamless Rust ecosystem interop
• Language Server - IDE support with completions
• JIT Compilation - Hot path optimization
• Refinement Types - SMT-backed verification

Performance

Generated Rust code achieves zero runtime overhead compared to handwritten Rust.

Project Structure

ruchy/
├── src/
│   ├── frontend/          # Lexer, Parser, AST
│   ├── middleend/         # Type system, inference
│   ├── backend/           # Rust code generation
│   └── runtime/           # REPL and interpreter
├── ruchy-cli/             # Command-line interface
├── examples/              # Example programs
├── tests/                 # Integration tests
└── docs/                  # Documentation

Contributing

1. Quality Standards: All code must pass linting, testing, and coverage requirements
2. No SATD: Use GitHub issues instead of TODO comments
3. Property Tests: Every feature needs property-based tests
4. Performance: No regressions in compilation speed

See docs/project-management/CLAUDE.md for detailed development guidelines.

Testing

# Run all tests
make test

# Check code coverage (must be >75%)
make coverage

# Run linting
make lint

# Run specific test
cargo test test_name

License

MIT License - See LICENSE file for details.

Citation

@software{ruchy2025,
  title = {Ruchy: A Systems Scripting Language with Rust Transpilation},
  author = {PAIML Contributors},
  year = {2025},
  url = {https://github.com/paiml/ruchy},
  version = {0.2.1}
}

Building tomorrow's scripting language with today's systems programming practices.