Holes in GHC

Thijs Alkemade thijsalkemade at gmail.com
Fri Feb 10 14:06:34 CET 2012

Hello all,

We've started a wiki-page discussing how this idea can be applied to GHC here:


There have already been a number of people who indicated they'd want
to use this, so feel free to use the page to leave your comments about
how you'd want to use it.

Any comments on the best way to implement it are welcome too. We are
currently working with the idea of named holes[1], for which we are
not using the method mentioned in our earlier mails, but we're working
on an implementation more similar to how implicit parameters work.
I.e. generating constrains when a hole is encountered, so the same
name used multiple times will be inferred correctly. However, these
should propagate differently from implicit parameters and should not
create an error when the constraint is not in the type signature.

Thijs Alkemade

[1] http://hackage.haskell.org/trac/ghc/wiki/Holes#Namedholes

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