Hi,
I think there is a typo in the definition of the function "tree", in the
module "Ldfs.hs", which is in the demos directory of the hugs distribution.
The original definition is:
tree :: Bounds -> Forest Vertex -> Graph
tree bnds ts = buildG bnds (concat (map flat ts))
where flat (Node v rs) = [ (v, w) | Node w us <- ts ] ++
concat (map flat ts)
I think it should be:
tree :: Bounds -> Forest Vertex -> Graph
tree bnds ts = buildG bnds (concat (map flat ts))
where flat (Node v rs) = [ (v, w) | Node w us <- rs ] ++
concat (map flat rs)
The difference is that I have changed "ts" to "rs" in the body of the
function "flat".
By the way, I find Ldfs very useful and I think it deserves a place amongst
the libraries. I have attached a modified version of Ldfs that I often use.
It is based on FiniteMap and Set, rather than arrays, because I tend to
find that my graphs do not use integer indices. Of course, this means that
my version is less efficient than the original and does not use LazyST, but
I have never yet had any problems with its performance. Provided that
Professor Launchbury agrees, would it be possible to add it to the
libraries? If some work needs to be done to bring it into line with
existing style guides, then I am happy to do this.
Kevin
(See attached file: Ldfs.hs)
Kevin Backhouse, Software Engineer
ARM Limited
110 Fulbourn Road, Cambridge, CB1 9NJ, UK.
Tel: +44 1223 400601
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