Polymorphic lists...

[MR K P SCHUPKE]

I needed a list which could handle items of different types for the 
database code I am writing. I have written a module implementing such a 
list based on dependant types (from Conor McBride: Faking It; Simulating 
Depandant Types in Haskell). Although McBride does not mention 
lists/vectors with items of differing types, the solution to 
implementing them came from his 'nthFront' function for re-arranging the 
order of arguments to a function.

Any type can be inserted into the list, which supports 
head/tail/init/last, as well as indexed lookup, and a cartesian-product 
(concatenating two lists together). I have included fromTuple/toTuple as 
well.

This seems quite a useful construct, and if there is nothing similar in 
the standard libraries at the moment, do you think this is worth including?

   Regards,
   Keean Schupke.
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