Constraint Kinds

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Thu 3 Nov 2011

What Constraints Entail: Part 2

Posted by Edward Kmett under Constraint Kinds , Haskell , Logic , Monads , Type Hackery , Uncategorized
[13] Comments 

Last time we derived an entailment relation for constraints, now let's get some use out of it.

Reflecting Classes and Instances

Most of the implications we use on a day to day basis come from our class and instance declarations, but last time we only really dealt with constraint products.

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Thu 3 Nov 2011

What Constraints Entail: Part 1

Posted by Edward Kmett under Category Theory , Constraint Kinds , Haskell , Logic , Monads , Type Hackery , Uncategorized
[4] Comments 

Max Bolingbroke has done a wonderful job on adding Constraint kinds to GHC.

Constraint Kinds adds a new kind Constraint, such that Eq :: * -> Constraint, Monad :: (* -> *) -> Constraint, but since it is a kind, we can make type families for constraints, and even parameterize constraints on constraints.

So, let's play with them and see what we can come up with!

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