Greyalien Language (Prototype)

This is a prototype implementation of the Greyalien language concept: a new, experimental programming language designed to surpass traditional systems languages in clarity and safety.

This ZIP includes:

• SPEC.md – Greyalien v0 conceptual language design.
• SPEC_V0.md – the subset spec implemented by this interpreter.
• GREYALIEN_CORE.md – core design principles.
• GREYALIEN_VISION.md – long-term vision and roadmap.
• compiler_architecture.md – high-level architecture for a future native Greyalien compiler.
• LICENSE – MIT license.
• CONTRIBUTING.md – contribution guide.
• CHANGELOG.md – release notes.
• RELEASE.md – release checklist.
• ROADMAP.md – v0.2 scope and priorities.
• TRIAGE.md – issue triage guide.
• Makefile – release helper targets.
• greyalien/ – a minimal Greyalien interpreter implemented in Python for a small v0 subset.
• examples/ – runnable .grl programs.

Note: The interpreter is intentionally small. It runs a Greyalien subset with functions, conditionals, loops, records, lists, match expressions, enums, imports, arithmetic, booleans, and printing. It is meant as a working playground, not a production compiler.

A minimal static type checker for Int, Bool, and String runs before execution and reports type errors.

What's new in v0.3.0

• match expressions, enums, and enum payloads.
• Module imports with a minimal loader.
• Conformance fixtures and parser fuzz coverage.

Unreleased (main branch)

• Scoped module namespaces (imports require qualification, e.g. math.add(...)).
• Explicit exports (export { ... }) control module visibility.
• Exported enums are type-only; variants must be listed explicitly.
• Enum payload bindings in match patterns (for example, Some(x)).
• Module-qualified enum types in annotations (for example, colors.Color).

Requirements

• Python 3.9+

Install from PyPI

python -m pip install greyalien-prototype

Create a file hello.grl:

fn main() {
  print("Hello from Greyalien!");
}

Run it:

greyalien run hello.grl

Install from source

python -m pip install -e .

Then run:

greyalien run examples/hello.grl

Running examples

From the directory where you unpack the ZIP:

python -m greyalien.cli examples/hello.grl

Or with the unified CLI:

python -m greyalien run examples/hello.grl

You should see:

Hello from Greyalien!

Another example:

python -m greyalien.cli examples/math.grl

Or:

python -m greyalien run examples/math.grl

Expected output:

Result is 42

Module example with qualified enum types:

python -m greyalien run examples/modules/type_qual_demo.grl

Expected output:

red

Logic example:

python -m greyalien.cli examples/logic.grl

For-loop example:

python -m greyalien.cli examples/for_demo.grl

Typed example:

python -m greyalien.cli examples/typed.grl

Record example:

python -m greyalien.cli examples/records.grl

List example:

python -m greyalien.cli examples/list_demo.grl

Match example:

python -m greyalien.cli examples/match_demo.grl

Enum example:

python -m greyalien.cli examples/enum_demo.grl

Enum payload example:

python -m greyalien.cli examples/enum_payload_demo.grl

Module/import example:

python -m greyalien.cli examples/modules/module_demo.grl

Running tests

python -m unittest discover -s tests

Maintainer notes

• Issue triage flow and labels: TRIAGE.md
• Label definitions live in .github/labels.yml and sync via the Label Sync workflow

Type checking only

python -m greyalien check examples/typed.grl

CLI quick reference

greyalien <file.grl>
greyalien run <file.grl>
greyalien check <file.grl>
greyalien ir <file.grl>
greyalien --all-errors <file.grl>
greyalien run --all-errors <file.grl>
greyalien check --all-errors <file.grl>
greyalien --version
greyalien --help

CLI help example

greyalien --help

Usage:
  greyalien <file.grl>
  greyalien run <file.grl>
  greyalien check <file.grl>
  greyalien ir <file.grl>
  greyalien --all-errors <file.grl>
  greyalien run --all-errors <file.grl>
  greyalien check --all-errors <file.grl>
  greyalien --version
  greyalien --help

Options:
  --all-errors  Show all parse errors instead of the first.

Parse error diagnostics

Use --all-errors to report every parse error in one run:

greyalien check --all-errors examples/for_demo.grl

Subset supported by the interpreter

• Optional module declaration (ignored at runtime):

  module main
  

• Function definitions:

  fn main() {
    print("Hello");
  }
  
  fn add(a, b) {
    return a + b;
  }
  

• Optional type annotations (checked before execution):

  fn add(a: Int, b: Int) -> Int {
    return a + b;
  }
  
  fn main() {
    let x: Int = 1;
    print("x = " + x);
  }
  

  Type errors include line/column locations where available.

• let bindings inside functions:

  fn demo() {
    let x = 10;
    let y = x * 2;
    print(y);
  }
  

• set assignments to update existing bindings:

  fn demo() {
    let count = 0;
    set count = count + 1;
  }
  

• while loops:

  fn demo() {
    let i = 0;
    while i < 3 {
      print(i);
      set i = i + 1;
    }
  }
  

• for loops over integer ranges:

  fn demo() {
    for i in 0..10 by 2 {
      print(i);
    }
  }
  

  Use start..end for exclusive ranges or start..=end for inclusive ranges. Add by step to control the step size.

• break and continue inside loops:

  fn demo() {
    for i in 0..10 {
      if i == 2 { continue; } else { print(i); };
      if i == 5 { break; } else { 0; };
    }
  }
  

  fn demo() {
    let i = 0;
    while true {
      set i = i + 1;
      if i == 2 { continue; } else { 0; };
      if i == 4 { break; } else { 0; };
    }
  }
  

• return statements in functions.

• Expressions:

  • Integer literals: 1, 42
  • String literals: "hello"
  • Boolean literals: true, false
  • Record literals: {x: 1, y: 2}
  • List literals: [1, 2, 3]
  • Unary operators: -expr, !expr
  • Binary operators: +, -, *, /, ==, !=, <, <=, >, >=, &&, ||
  • Field access: expr.field
  • Indexing: expr[index]
  • Parentheses: (expr)
  • if expressions: if cond { expr; } else { expr; }
  • else if is supported as sugar for else { if ... }

• Function calls: name(arg1, arg2)

• Built-in print(...) for output.

Types supported by the checker: Int, Bool, String, Unit.

Anything else will result in a parse or runtime error.

Example Greyalien program

module main

fn main() {
  let a = 40;
  let b = 2;
  let result = a + b;
  print("Result is " + result);
}

This runs on the interpreter and prints:

Result is 42

Enjoy experimenting with Greyalien!