[Haskell-cafe] Re: Implementing fixed-sized vectors (using datatype algebra?)

Wolfgang Jeltsch g9ks157k at acme.softbase.org
Thu Feb 7 05:17:48 EST 2008

Am Donnerstag, 7. Februar 2008 02:47 schrieb Alfonso Acosta:
> > The other library I use for type-level programming is HList. It has
> > type-level booleans already so you might what to take a look at it if
> > you're not already familiar with it.
> Thanks I'll have a look at it.

I have to admit that I don’t like the names HBool, HTrue and HFalse.  What do 
they mean?  Heterogenous booleans?  Heterogenous truth?  Why it’s “Bool” 
instead of “Boolean” and therefore not conforming to the Prelude convention?

Heterogenous lists are not directly about type level computation.  A HList 
type is usually inhabited.  On the other hand, types which denote type level 
naturals or type-level booleans are empty data types.  So type level booleans 
should go into some type level programming library like the one Alfonso and I 
want to create.  HList should then use these booleans.  This is at least my 

Best wishes,

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