Leopard

Leopard is a small, beginner-friendly programming language for writing desktop GUI programs: windows, controls, menus, turtle graphics, editable text windows, and sound. It's a from-scratch, modernized resurrection of leopard.bas, a 2013 Liberty BASIC application by Brandon Watts — this time a real language, with variables, expressions, control flow, functions, and lists, rather than a fixed-vocabulary state machine.

window "Hello", 300, 100:
    label "Hello, world!" as greeting at 10, 10, 200, 24

pip install -e ".[gui]"
leopard run hello.lep

Installing

Leopard is a standard pip package (leopard-lang), split into optional extras so you only install what you need:

pip install -e .              # the language core only — no GUI dependency at all
pip install -e ".[gui]"       # + PyQt6, needed for window/menu/turtle/sound programs
pip install -e ".[build]"     # + PyInstaller, needed for `leopard build`
pip install -e ".[dev]"       # + pytest, for running this project's own test suite

A bare (no-window) script never needs PyQt6 installed at all — the language core has zero GUI dependency.

Using the CLI

leopard run script.lep              # run a program
leopard build script.lep            # compile it into a standalone executable
leopard build script.lep -o dist -n myapp

leopard build bundles your script's source, the Leopard runtime, and a small generated launcher into one --onefile PyInstaller executable — no Python installation required on the machine that runs it.

Learning Leopard

• LANGUAGE_GUIDE.md — start here. A tutorial that walks through every part of the language with runnable examples.
• GRAMMAR.md — the complete, precise language spec: every keyword, operator, and builtin, with exact rules. The source of truth the guide is derived from.
• Example curriculum — sixteen sample programs in the companion Leopard IDE repository, from bare-script fundamentals through every window kind to two capstone projects. See that folder's own README for the full, ordered list.

The Leopard IDE

Leopard is fully usable from the command line with any text editor, but a dedicated IDE also exists, in its own separate repository: github.com/CFFinch62/LEOPARD-IDE — syntax highlighting, a run/build toolbar, a file browser, and the example curriculum above, all built on this package (leopard-lang). Install this package first (see Installing, above), then follow that repo's own README.

Project layout

LANGUAGES/Leopard/
  original -source/leopard.bas   <- original 2013 source, read-only reference
  GRAMMAR.md                <- canonical language spec
  LANGUAGE_GUIDE.md          <- beginner tutorial
  IMPLEMENTATION_PLAN.md     <- project tracker / build history
  pyproject.toml
  src/leopard_lang/
    tokens.py, lexer.py, ast_nodes.py, parser.py    <- lexer/parser
    errors.py, environment.py, interpreter.py        <- runtime core
    builtins_core.py, builtins_files.py              <- non-GUI builtins
    cli.py                                           <- `leopard` command
    build.py                                         <- `leopard build` / PyInstaller packaging
    gui/                                              <- windows, menus, turtle, text window, sound
  tests/

Development

pip install -e ".[dev,gui,build]"
pytest

299 tests, headless (QT_QPA_PLATFORM=offscreen set automatically in tests/conftest.py), a few seconds to run. See IMPLEMENTATION_PLAN.md for the full build history and design decisions behind the language.

Acknowledgments

Leopard's vocabulary and spirit — window/text-window/graphics-window programs, named GUI controls, turtle graphics — come from Brandon Watts's original 2013 Liberty BASIC application, leopard.bas (original -source/leopard.bas, and originally distributed via leopardprogramming.com). This project is a ground-up reimplementation as a real programming language, but the idea and design it draws inspiration from are his.

License

MIT — see LICENSE.