[Haskell-cafe] fast, strongly typed heterogeneous collections

[Alberto G. Corona]

Hi

What is the speed of hProjectByLabel/s in Data.HList.Record? . The
documentation in hackage
<http://hackage.haskell.org/packages/archive/HList/latest/doc/html/Data-HList-Record.html#t%3AH2ProjectByLabels>does
not mention it. Perhaps this is because Hlist is designed for supposedly
short records and this does not matter too much.
 looking at the code I guess that everything in HList is O(n) because it
uses type-level list structure, but I think that nothing prevents from using
a type level balanced tree, Data.Map style, instead.

This would permit to implement large heterogeneous Maps with fast access
and strongly typed. AFAIK, the alternative is to use a fast data container
with data elements encapsulated within Data.Dynamic, that is weakly typed,
produces type errors at runtime, which is unsatisfactory and dangerous.


Any comments?
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