Too heavy for its own good.

About

Experimental programming language with its own VM implemented in C.

Build

./build.sh

This creates 4 binaries: debug, release, valgrind & valgrind (with GC stress enabled)

Note

You can also refer to legacy tree walk interpreter implementation in CPython.

Usage

Sample program(BST), create file named test.gus:

class Tree {
    init(value) { this.value = value; this.left = this.right = nil; }

    insert(value) {
        if (value < this.value) {
            if (this.left == nil) { this.left = Tree(value); } 
            else { this.left.insert(value); }
        } else {
            if (this.right == nil) { this.right = Tree(value); }
            else { this.right.insert(value); }
        }
    }
}

fun binary_search(node, value) {
    if (node == nil) return false;
    if (node.value == value) return true;
    if (value < node.value) return binary_search(node.left, value);

    return binary_search(node.right, value);
}

var root = Tree(10);

root.insert(5); root.insert(15); root.insert(3); root.insert(7);

stdout Tree;
stdout root;
stdout binary_search(root, 7);
stdout binary_search(root, 15);
stdout binary_search(root, 12);
stdout binary_search(root, 5);

[gustav] # ./target/gustav_release ./test.gus
Gustav v1.0.0 [ git_branch=master git_commit=fd864dd | Aug  4 2026 03:34:11] [ Clang 19.1.7 (3+b1) ] | optimized RELEASE build for "Linux x86_64"

Tree
Tree<Instance>
true
true
false
true

Testing

Note

Current state of tests - all passing. There are features that should be implemented (they're excluded from test cases):

• Loop Statement
• Break & Continue Statements
• Ternary Expressions
• Lambda functions/expressions
• Pipe operator Since, they were not in original "plan" - they're in TODO (rather than being main feature)

Install pytest via uv (or whataver):

uv tool install pytest
pytest -vv tests