On Fri, Apr 3, 2009 at 9:30 PM, Heinrich Apfelmus wrote: Zachary Turner wrote: I thought I would try to see if it were possible to write, in point-free
form using no lambda functions and no intermediate functions, a function
that takes 2 lists of Booleans, computes the pairwise logical AND of the
two
lists, and returns a list containing the 0 based indices of the elements
where the logical and of the two was true. I know that at some point it
becomes overkill and for the sake of readability one should know when to
draw the line. So I want to see if someone with more experience than me
can
comment on whether or not this is over the line :P trueIndices = curry $ map fst . filter snd . zip [0..] . map (uncurry
(&&))
.. (uncurry zip) So do all the uncurries and curries make it too hard to understand or is
it
pretty easy to read this? For me it takes me a while to figure out by
looking at it because it's hard to trace all the currying and uncurrying.
And is there a more elegant solution? Looks very readable to me, though I'd write it as trueIndices = (map fst . filter snd . zip [0..] .) . zipWith (&&) or even simply as trueIndices xs ys =
map fst . filter snd . zip [0..] $ zipWith (&&) xs ys because composing functions with more than one argument tends to be a
bit messy. With Conal's semantic editor combinators http://conal.net/blog/posts/semantic-editor-combinators/ it would be written as trueIndices =
(result . result) (map fst . filter snd . zip [0..]) (zipWith (&&)) That was a pretty interesting blog post, and easily understandable which is
always nice. Thanks for the link. I also had never even used the zipWith
function, so thanks for pointing out that equivalence.