I guess you want an automatically derived show that indents, but if
you don't mind defining you own, Data.PrettyPrint is really nice.
Here is an example that produces roughly the same as your example:
import Data.PrettyPrint
tree2doc Leaf = text "Leaf"
tree2doc (Bin x l r) =
text "Bin" $$
nest 2 (text (show x) $$
tree2doc l $$
tree2doc r)
showTree = render . tree2doc
/Johan
2012/3/13 Johan Tibell <[email protected]>:
> Hi all,
>
> The derived Show instance is useful, but I sometimes wish for
> something that's easier to read for big data types. Does anyone have
> an implementation of show that draws things in a hierarchical manner?
> Example:
>
> Given
>
> data Tree a = Leaf | Bin Int a (Tree a) (Tree a)
>
> and
>
> value = Bin 1 (Bin 2 Leaf Leaf) (Bin 3 Leaf Leaf)
>
> draw as
>
> Bin
> 1
> Bin
> 2
> Leaf
> Leaf
> Bin
> 3
> Leaf
> Leaf
>
> Cheers,
> Johan
>
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