-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 8/2/10 17:18 , Stefan Holdermans wrote:
Brandon,
h :: (x ~ y, Eval (y -> Int)) => (x -> Int) -> (y -> Int) -> Int
But actually if you push the constraint inward, into the type so to say, you actually get quite close to Janis' and David's solution.
Sorry, I was thinking out loud there. I meant the Eval constraint, not the equality constraint. But, right now, I guess my comment only makes sense to me, so let's pretend I kept quiet. ;-)
The point of this discussion is that the Eval constraint needs to be on one of the functions. So I tried to specify that (x -> Int) and (y -> Int) are different types despite x and y being the same type, because one of them has an Eval constraint. This may be a shortcoming of Haskell (or System Fc?) types, although it may be doable with a newtype. - -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkxXWZUACgkQIn7hlCsL25XhxACdFLFtCUrJqEpqGSsymt1uE3Zc yWgAoKcyJZdjng1zthyAtPkMCIvHce27 =XkFz -----END PGP SIGNATURE-----