first-class polymorphism beats rank-2 polymorphism
Mon, 11 Mar 2002 02:46:55 -0800
| Looking at the type of sequ,
| the foralls for t end up at the top.
| Hence, I have no chance to define sequential
Indeed the foralls are at the top, but I claim that wherever
you could use the composition function you were expecting,
you can also use the one GHC gives you. The two types
Let me know if you find a situation where this isn't true.
| Please let me know if this is a bug.
No I believe it is not a bug. I would be interested to see why you
needed to change your code.
| I just realized that type synonyms in GHC seem to be valid=20
| arguments even when not completely instantiated? This is=20
| wonderful. It is not supported in hugs. How difficult is it=20
| to cope with this? Does it make a real difference for the type system?
No, GHC does not support partially applied type synonyms,=20
except in the RHS of other type synonyms. It is a VERY BIG thing to
allow this, because it amounts to allowing lambdas at the type level
and that messes up inference cruelly.
Why do you think GHC does?