[Haskell-cafe] Implementation of "Dynamic" datatype

[Isaac Dupree]

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Stefan O'Rear wrote:
> On Sat, Mar 03, 2007 at 09:18:00AM +0000, Lennart Augustsson wrote:
>> Why would there be an extra function?
> Because the compiler can't statically prove that the typeRep field of
> the dictionary doesn't depend on its argument.  Therefore, the
> function cannot be unpacked.  (Or can it?  Could hbc?)

Unfortunately it would be difficult for the compiler to know that no-one
is going to make an instance that does depend on its argument (as long
as it does not do full-program analysis to determine the layout of data
structures). Maybe there should be some sort of annotation on class
method arguments that are supposed to be ignored, even if only a pragma,
if it would help compilers figure this out.

Isaac

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