Take this obscure function:
\begin{code}
func :: (a -> a -> Maybe a) -> a -> [a] -> [a]
func f s0 xs0 = foldr (\x xs s -> maybe (xs s) ((x:) . xs) (f s x))
return xs0 s0
\end{code}
And mergeGroupToList becomes:
\begin{code}
mergeGroupToList g xs = func mergeGroups g xs
\end{code}
Cheers,
Spencer Janssen
On Jan 11, 2007, at 11:37 AM, Seth Gordon wrote:
I have a data type "Group", representing a group of geographic
information that is all referring to the same location, and a function
"mergeGroups" that tries to merge two groups:
mergeGroups :: Group -> Group -> Maybe Group
Then I have a function "mergeGroupToList" that tries to merge its
first
argument with every element of the second argument:
mergeGroupToList :: Group -> [Group] -> [Group]
mergeGroupToList g [] = [g]
mergeGroupToList g1 (g2:gs) =
case (mergeGroups g1 g2) of
Nothing -> g2 : (mergeGroupToList g1 gs)
Just g3 -> mergeGroupToList g3 gs
How can I rewrite mergeGroupToList in terms of foldr?
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