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README.md

Vera Language for Visual Studio Code

Syntax highlighting and language support for the Vera programming language — a statically typed, purely functional language with algebraic effects, mandatory contracts, and typed slot references (@T.n), designed for LLM-generated code.

Features

Syntax highlighting for the full Vera language, including constructs that have no equivalent in other languages:

  • Slot references — @Int.0, @Array<String>.1, @Nat.result, and bare @Type bindings in match arms are all highlighted distinctly, since they are the primary way Vera code refers to values.
  • Contract blocks — requires, ensures, effects, decreases, and invariant are scoped separately from control flow keywords, so colour themes can distinguish verification annotations from program logic.
  • Effects — built-in effects (IO, State, Exn, Http, Async, Diverge) and qualified operation calls (IO.print, Exn.throw) are highlighted with their components broken out.
  • String interpolation — \(...) expressions inside strings get full Vera highlighting.
  • Nestable block comments — {- ... {- ... -} ... -} handled correctly.

Language configuration so VS Code understands Vera's structure:

  • Toggle line comments with Cmd+/ (uses --)
  • Toggle block comments with Shift+Alt+A (uses {- ... -})
  • Bracket matching and auto-closing for {}, [], (), <>, "", and {- -}
  • Code folding on brace blocks
  • Auto-indentation on { / }
  • Word selection that understands slot references as single tokens

Installation

From source (recommended for now)

Fresh clone:

git clone https://github.com/aallan/vera.git
ln -s "$(pwd)/vera/editors/vscode" ~/.vscode/extensions/vera-language

Existing clone (run from the repo root):

ln -s "$(pwd)/editors/vscode" ~/.vscode/extensions/vera-language

Then reload VS Code. Any .vera file will be recognised automatically.

From VSIX

If a packaged .vsix is available:

code --install-extension vera-language-0.1.0.vsix

VS Code Marketplace

Not yet published. This is planned once the language reaches a stable release.

Scope reference

The grammar uses standard TextMate scope conventions, so it works with any colour theme. Key assignments:

Vera construct Scope
@Int.0, @Array<String>.result variable.other.slot.vera
@Int (in match binding) variable.other.slot-binding.vera
requires, ensures, effects keyword.contract.vera
if, match, let, handle keyword.control.vera
fn, data, effect, import keyword.declaration.vera
public, private storage.modifier.vera
IO, State, Exn entity.name.type.effect.vera
IO.print, Exn.throw effect + entity.name.function.effect-op.vera
Some, None, Ok, Err entity.name.tag.constructor.vera
Int, Bool, String storage.type.primitive.vera
Array, Option, Result storage.type.composite.vera
true, false, pure constant.language.vera
-> keyword.operator.arrow.vera
` >`

Links

Licence

MIT