Henning Thielemann wrote:
On Thu, 12 Jun 2008, Isaac Dupree wrote:
Henning Thielemann wrote:
On Wed, 11 Jun 2008, Isaac Dupree wrote:
"extractHead" is an ugly name for a nevertheless standardish-meaning
function... what is it usually called? uncons? headTail?
(Data.Sequence, which is meant to be left-right symmetric, calls it
"viewr"... except your version doesn't have the Maybe, it's partial
instead, fails on empty lists)
I like the 'viewL' and 'viewR' kind of functions, they are safer than
'head' and 'tail', 'init' and 'last'. But since in most cases I used
'viewL' in connection with 'maybe', the continuation style functions
switchL :: b -> (a -> Seq a -> b) -> Seq a -> b
switchR :: b -> (Seq a -> a -> b) -> Seq a -> b
I think you got L and R backwards?
Why do you think so?
http://cvs.haskell.org/Hugs/pages/libraries/base/Data-Sequence.html#v%3Aviewl
Because I was confused. Looking again, you seem to be right...
it's a little confusing to me, but following Data.Sequence I think
they're meant to match whether repeated L or R makes a foldl or a foldr.
viewl is like a 'case' for distinction of [] and (:) and thus can be
used to implement both foldl and foldr.
yes, but in the sense that foldr is more "natural" for lists than foldl,
requiring just replacing the constructors "directly"
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