[Haskell-cafe] Block-wise lazy sequences in Haskell

[Henning Thielemann]

  I want to have a data structure like Data.ByteString.Lazy, that is 
block-wise lazy, but polymorphic. I could use a lazy list of unboxed 
arrays (UArray) but the documentation says, that the element types are 
restricted. But I will need (strict) pairs of Double and the like as 
elements. It seems that I need generalized instances in order to use these 
arrays.
  I thought it must be possible to define an unboxed array type with 
Storable elements. I cannot find such a type in the standard libraries. 
Further on, I wonder why pairs are not instances of Storable.