Loft

Loft is a new programming language designed to provide a Rust-like development experience with a focus on simplicity and expressiveness. This project is currently in alpha stage.

[!WARNING]

IMPORTANT: Loft is currently in very early development (v0.0.1-alpha) and should be considered experimental. Many features are incomplete, unstable, or subject to significant changes. The language is not yet suitable for production use.

• The syntax and semantics may change without notice
• The standard library is minimal and constantly evolving
• Error messages might be unhelpful or confusing
• Performance optimization has not been a priority yet
• Documentation is sparse and may be outdated
• Memory safety guarantees are still being implemented

Use at your own risk, and please report any issues or bugs you encounter to help improve the language!

Overview

Loft combines the safety and expressiveness of Rust with a more approachable learning curve. Key features include:

• Strong static typing
• Pattern matching
• First-class macros
• Support for structs and enums
• Ownership and borrowing semantics
• Safe memory management without a garbage collector

Implementation Architecture

Loft is currently implemented as an interpreted language, though future versions may include compilation targets. The implementation consists of several key components:

Interpreter

The language uses a token-based interpreter with the following pipeline:

1. Lexing: Source code is tokenized by the lexer (src/parser/lexer.rs), which converts raw text into tokens.
2. Parsing: The parser (src/parser/mod.rs) transforms tokens into an abstract syntax tree (AST).
3. Runtime Interpretation: The interpreter (src/runtime/interpreter.rs) walks through the AST and executes each node.
4. Value Representation: Values are represented at runtime through the ValueType enum (src/runtime/value.rs).

The interpreter design is modular, with separate components handling:

• Expressions and statements
• Control flow (conditionals, loops)
• Pattern matching
• Macro expansion
• Struct and enum operations
• References and borrowing

Typing System

The type system is currently dynamic at runtime but with strong type checking. A more comprehensive static type checking system is in development in src/types/checker.rs, but is not fully implemented or integrated yet.

Macros

The macro system is a significant work in progress, with temporary implementations visible in src/runtime/interpreter/macro/. Macros are parsed and expanded during runtime with a declarative pattern-matching approach.

Memory Management

The memory model uses reference counting (via Rust's Rc<RefCell<>>) to manage object lifetimes. The borrowing and ownership semantics are partially implemented but not yet fully aligned with Rust's guarantees.

Current Development Focus

The project is actively working on:

1. Expanding the standard library - Currently minimal, as seen in src/std/prelude.lo
2. Improving the type checker - Moving toward static analysis
3. Refactoring the macro system - Making it more robust and compatible with Rust's approach
4. Enhancing error reporting - Providing more helpful diagnostics
5. Implementing missing language features - Closures, traits, and more complete pattern matching

Examples

Hello World

fn main() {
    println!("Hello, world!");
}

FizzBuzz

fn main() {
    for x in 1..=30 {
        match (x % 3, x % 5) {
            (0, 0) => println!("FizzBuzz"),
            (0, _) => println!("Fizz"),
            (_, 0) => println!("Buzz"),
            _ => println!("{x}"),
        }
    }
}

Structs and Methods

struct Triangle {
    base: f64,
    height: f64,
    info: Info
}

struct Info {
    id: u8,
    name: &str,
}

impl Triangle {
    fn new(base: f64, height: f64, name: &str, id: u8) -> Self {
        Self { base, height, info: Info { name, id } }
    }

    fn display(&self) {
        println!("Triangle: base={}, height={}, id={}, name={}",
                self.base, self.height, self.info.id, self.info.name);
    }
}

Installation

From Source

git clone https://github.com/themackabu/loft
cd loft
cargo install --path .

Or using the provided Maidfile:

maid install

Language Features

Types

Loft supports a variety of primitive types:

• Integers: i8, i16, i32, i64, i128, isize
• Unsigned integers: u8, u16, u32, u64, u128, usize
• Floating point: f32, f64
• Boolean: bool
• Strings: str
• Unit type: ()

Pattern Matching

let result = match value {
    Ok(n) => n,
    Err(_) => -1,
};

Macros

macro_rules! log {
    (error, $($arg:tt)*) => {
        println!("\x1b[31;40m[ERROR] {}\x1b[0m", format!($($arg)*))
    };
    (info: $($arg:tt)*) => {
        println!("\x1b[94m[INFO] {}\x1b[0m", format!($($arg)*))
    };
}

Ownership and References

fn test_assignment(val: &mut i32) -> &mut i32 {
   *val += 3;
   return val;
}

fn main() {
   let mut value = 5;
   let val2 = test_assignment(&mut value);
   *val2 += 10;
}

Running Loft Programs

Direct Execution

loft your_program.lo

With the Maidfile

maid run your_program.lo

As a Script (with shebang)

#!/usr/bin/env loft
fn main() {
   println!("Running as a script!")
}

Make it executable and run:

chmod +x script.lo
./script.lo

Testing

Run test files:

maid test array # run tests/array.lo
maid test-all # run all tests

Project Structure

• src/ - Core language implementation
  • loft/ - Core language components
  • parser/ - Lexer and parser
  • runtime/ - Interpreter and runtime
  • types/ - Type system (work in progress)
  • std/ - Standard library (minimal)
• tests/ - Test programs

Contributing

Due to the early stage of development, the API and language design are highly volatile. However, contributions are welcome in the form of:

• Bug reports and test cases
• Feature suggestions
• Documentation improvements
• Performance optimizations