Cognate Playground

Canonical instance: https://cognate-playground.hedy.dev/

An interactive playground for Cognate that uses a JavaScript implementation of Cognate.

It currently supports about 90% of all builtins from the C prelude, and all types except IO. Discrepancies of this implementation that can be illustrated by tests can be found with XFAIL markers in the tests directory.

Files of interest

• index.html
• cognate.js -- the parser, linter, and runtime
• main.js -- the rest of the app excluding the editor
• editor/* -- code relating to the editor component
• public/tree-sitter.{js,wasm} -- from tree-sitter releases
• public/tree-sitter-cognate.wasm -- built from tree-sitter-cognate
• public/prelude.cog -- definitions of various built-in functions. copied from the Cognate repo with only I/O builtins commented out. eventually it will simply link to the prelude.cog file from the Cognate repo.

Todo

The runtime and cognate implementation

• Working interpreter
• Escape HTML
• Proper "types"
• Scoping
• Support symbols and floats
• Support Set (temporarily) to update values from outer scope
• Function shadowing
• Fix lexical scoping
• Support List
• Support hoisting
• Allow shadowing things in the prelude and builtins
• Fix Print; Add Show
• Update Prelude from upstream
• Add Stack
• Add string methods
• Support Box and a proper Set
• String escape sequences
• Prevent stack overflows
• Explore optimization options, consider feasibility of transpiling to JS or using bytecode
• Standard library coverage
• Closures
• Tests
• Consider using something like decimal.js for floating point precision
• Mock I/O
• Table

The Playground

• Presets of example code
• Save input in localstorage
• Live syntax highlighting
• [perf] Collect all tokens to be highlighted, and dispatch them in batch
• [perf] Avoid re-evaluating the prelude each time
• [perf] Send edits to tree-sitter instead
• Use worker thread for the runtime
• Allow stopping current execution with a button
• Auto-eval after a timeout, merging several successive edits in one
• (1) Highlight references of functions in scope
• Show parser errors inline in the editor
• More informative runtime errors
  • Format the traceback similar to Python (or Web Console)
  • Collapse recursive calls and show surrounding code(?)
  • Clicks on symbols can navigate to the definition/reference in the editor
• Fix (1); highlight with static analysis rather than at runtime
• [perf] Find ways to accurately cache for (1)
• Handle failure to fetch prelude
• Fix tree-sitter edit conversions for pair wrapping (editor feature)
• Editor settings
  • Tooltip hints
  • Autocomplete
  • Tab handling
  • Auto eval - if not, show a Run button
• Lint for possible missing semicolons
• Special function, (or just Print) that allows exploring data structures interactively (similar to the Web Console) - but retain cognac behaviour with Show