[Haskell-cafe] Re: defining last using foldr

Chaddaï Fouché chaddai.fouche at gmail.com
Tue Aug 14 18:39:19 EDT 2007

2007/8/14, Aaron Denney <wnoise at ofb.net>:
> The problem with foldl is that you can't easily make it polymorphic
> because of how the null case is handled.  foldl1 and foldr1 are trivial,
> true.

The original "last" fail on empty list, it's far easier to obtain the
same semantic with foldl than with foldr, in fact it isn't hard at all
to make it polymorphic without hassle (contrary to the foldr case)
_if_ you remember that there _is_ a value in Haskell wich belongs to
every type.


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