README.md

cur

A language with static dependent-types and dynamic types, type annotations and parentheses, theorem proving and meta-programming.

Noun
cur (plural curs)

1. (archaic) A mongrel.
2. (archaic) A detestable person.

Disclaimer

Cur is currently under active hackery and is not fit for use for any particular purpose. It is fraught with unreadable code, errors, performance bugs, and hacks that should never have been written by a reasonable human being. These may or may not be fixed shortly.

Getting started

Easy mode: Install cur via raco pkg install cur.

Advanced mode: Cur is actually distributed as several packages. cur-lib provides the implementation and all standard libraries. cur-doc provides the documentation. cur-test provides a test suite and examples.

Try it out: open up DrRacket and put the following in the definition area:

#lang cur
(require
 cur/stdlib/bool
 cur/stdlib/nat)

(if true
    false
    true)

(: + (-> Nat Nat Nat))
(define + plus)
(+ z (s z))

Try entering the following in the interaction area:

(sub1 (s (s z)))

Don't like parenthesis? Use Cur with sweet-expressions:

#lang sweet-exp cur
require
 cur/stdlib/sugar
 cur/stdlib/bool
 cur/stdlib/nat

if true
   false
   true

define + plus

{z + s(z)}

See the docs: raco docs cur.

Going further

Open up cur-tests/cur/tests/stlc.rkt to see an example of the simply-typed lambda-calculus modeled in Cur, with a parser and syntax extension to enable deeply embedding.

Open up examples/proofs-for-free.rkt to see an implementation of the translation defined in Proofs for Free as a meta-program.

Open up cur-lib/cur/stdlib/tactics to see one way to implement tactics in Cur.

Open up anything in cur-lib/cur/stdlib/ to see some standard dependent-type formalisms.

Open up cur-lib/cur/curnel/model/core.rkt to see a model of the core language, <600 lines of code. Currently, this model is also the implementation, although that is likely to change for performance reasons.