[Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas
Hi All: I've been working through some details in these papers [1], [2] and noticed a language pragma configuration that I hope you can confirm. When using explicit foralls in a data constructor, it appears that GHC 7.4.2 requires Rank2Types in the Language pragma for what the papers consider rank 1 types. Here's an example: data T = TC (forall a b. a - b - a) Am I correct, or is there another extension? The ExplicitForAll does not appear to support rank 1 types in data constructors. 1. Practical Type Inference for Arbitrary-Rank Types. 2. A Direct Algorithm for Type Inference in the Rank 2 Fragment of the Second-Order Lambda Calculus. -- Rick ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas
At Thu, 05 Jul 2012 11:18:00 -0400, rickmurphy wrote: data T = TC (forall a b. a - b - a) The type of `TC' will be `(forall a b. a - b - a) - T', a Rank-2 type. -- Francesco * Often in error, never in doubt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas
On 05/07/12 17:18, rickmurphy wrote: Hi All: I've been working through some details in these papers [1], [2] and noticed a language pragma configuration that I hope you can confirm. When using explicit foralls in a data constructor, it appears that GHC 7.4.2 requires Rank2Types in the Language pragma for what the papers consider rank 1 types. Here's an example: data T = TC (forall a b. a - b - a) Am I correct, or is there another extension? The ExplicitForAll does not appear to support rank 1 types in data constructors. There is the PolymorphicComponents extension precisely for this use case. Twan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas
Thanks Francesco. And I did verify that ExplicitForAll does in fact allow Rank 1 Types in functions like the following ... f :: (forall a. a - a) -- Rick On Thu, 2012-07-05 at 16:28 +0100, Francesco Mazzoli wrote: At Thu, 05 Jul 2012 11:18:00 -0400, rickmurphy wrote: data T = TC (forall a b. a - b - a) The type of `TC' will be `(forall a b. a - b - a) - T', a Rank-2 type. -- Francesco * Often in error, never in doubt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
