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
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.
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