Another vote for
map (map (+1)) [[1,2],[2,3]]
though I rather prefer
(map . map) (+1) [[1,2],[2,3]]
or even
(map . map) (+1) $ [[1,2],[2,3]]
====
Jack Henahan
jhenahan@uvm.edu
On Aug 13, 2012, at 1:21 AM, Christopher Howard
Hi. Is the some generic, clean syntax to unwrap a nested list, modify the value, and put it back together? Say, for example, I have the list [[1,2],[3,4]] and want to add 1 to each inner element, resulting in [[2,3],[4,5]].
After reading about the list monad, I was rather excited, because I (mistakenly) thought something like this would work:
code: -------- a = do b <- [[1,2],[3,4]] c <- b return (c + 1) --------
That would be awesome, because I would be able to modify the list at each level of unwrapping, while leaving the code very neat and readable. However, what the above example actually does is produce a /single/ list from the values:
code: -------- *Main> a [2,3,4,5] --------
Obviously wishing won't change how the list monad works, but I thought it might be worth asking if there is some other monad or syntactic trick that does something along the lines of what I am looking for.
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