A magic typeclass that just does it.

This plugin allows you to write

{-# OPTIONS_GHC -fplugin GHC.JustDoIt.Plugin #-}
module Test where

import GHC.JustDoIt

foo :: ((a -> r) -> r) -> (a -> ((b -> r) -> r)) -> ((b -> r) -> r)
foo = (…)

without having to write the actual implementation of foo.

See examples/Demo.hs for a few examples of what this plugin can do for you.

ghc-justdoit: a GHC plugin to write the code for you

This is a prototype of a code synthesis plugin for GHC, which uses LJT proof search to instantiate a type.

Synopsis

{-# OPTIONS_GHC -fplugin=GHC.JustDoIt.Plugin #-}
module Test where

import GHC.JustDoIt

foo :: ((a -> r) -> r) -> (a -> ((b -> r) -> r)) -> ((b -> r) -> r)
foo = (…)

Missing bits

• The LJT might not be complete, due to insufficient backtracking.
• The implementation is very much unoptimized.
• It returns one solution, but not necessary the “best” one. But what is the “best” one?
• It ignores any recursive type, so it cannot do anything with lists. It would be much more useful if it could do some best-effort thing here as well.
• It ignores linear types, and will likely produce ill-typed expressions for them.

If someone wants to pick it up from here, that’d be great!

Related work

• Djinn and djinn-ghc
• exference
• curryhoward for Scala
• hezarfen for Idris

Contact

Please reports bugs and missing features at the GitHub bugtracker. This is also where you can find the source code.

ghc-justdoit was written by Joachim Breitner and is licensed under a permissive MIT license.