[Haskell-beginners] cleanest way to unwrap a list?
math.simplex at gmail.com
Mon Aug 13 07:59:38 CEST 2012
What about just
map (map f) xxs
where for your example
xxs == [[1,2], [3,4]]
f == (+1)
On 13/08/2012 1:21 AM, Christopher Howard wrote:
> 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
> After reading about the list monad, I was rather excited, because I
> (mistakenly) thought something like this would work:
> 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:
> *Main> a
> 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.
> Beginners mailing list
> Beginners at haskell.org
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Beginners