Why is there a space leak here?

Olaf Chitil olaf@cs.york.ac.uk
Tue, 29 May 2001 11:28:36 +0100

David Bakin wrote:
> That's a very nice visualization - exactly the kind of thing I was hoping
> for.  I grabbed your papers and will look over them for more information,
> thanks very much for taking the trouble! The animations you sent me - and
> the ones on your page - are really nice; it would be nice to have a system
> like HOPS available with GHC/GHCi (I understand it is more than the
> visualization system, but that's a really useful part of it).
> (I also found out that Hood didn't help for this particular purpose - though
> now that I see how easy it is to use I'll be using it all the time.  But it
> is carefully designed to show you ("observe") exactly what has been
> evaluated at a given point in the program.  Thus you can't use it (as far as
> I can tell) to show the data structures that are accumulating that haven't
> been processed yet - which is what you need to know to find a space
> problem.)

You can use GHood,
http://www.cs.ukc.ac.uk/people/staff/cr3/toolbox/haskell/GHood/ .
It animates the evaluation process at a given point in the program.
It doesn't show unevaluated expressions, but for most purposes you don't
need to see them. Most important is to see when which subexpression is
(an older version of Hood, which is distributed with nhc, also has an
animation facility)

At some time we also hope to provide such an animation viewer for our
Haskell tracer Hat. The trace already contains all the necessary


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