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Part of Yhc


Yhc Core is a way of dumping and using the internal representation of Yhc in an external project. The code related to this, including data types, is found in src/compiler/Core directory of the Yhc source code.

Haddock Documentation

Blog Posts

The following sequence of blog posts probably gives a useful introduction to Yhc Core.

Generating Core

To generate Core, simply give the compiler the option -core or -corep. For example, when compiling

module FibMain where
main xs = pam daeh xs
daeh (x:xs) = x
pam f [] = []
pam f (x:xs) = f x : pam f xs

You get the output

$ yhc -core FibMain.hs
======  Human Readable Core:
FibMain.pam v220 v221 =
    case v221 of
        Prelude.[] -> (Prelude.[])
        Prelude.: v222 v223 ->
            (Prelude.: (YHC.Internal._apply1 v220 v222) (FibMain.pam v220 v223))
FibMain.daeh v224 =
    case v224 of
         Prelude.: v225 v226 -> v225
         _ -> (Prelude.error (LAMBDA228))
    (prim_STRING "FibMain: Pattern match failure in function at 7:1-7:15.")
FibMain.main v227 = (FibMain.pam FibMain.daeh v227)

The -core option gives human readable Core output, in a style very similar to Haskell. The -corep option gives a deriving Show output of the Core, which can be read back in with read very easily. The machine Core also contains source code locations for statements.

Compared to GHC Core

  • Types - Yhc has none, GHC has lots.
  • Familiarity - Yhc looks like Haskell, GHC is somewhat related, but not as close.
  • Name mangling - Yhc preserves names much better.
  • Source locations - Yhc keeps these, GHC doesn't.


  • Catch - Case and Termination Checker for Haskell by Neil Mitchell. This takes Core as an input.
  • Dr Haskell - give hints to beginners about useful Haskell functions/idioms.