ANNOUNCE: GHood -- a Graphical Hood (pre-release)

Thu, 04 Jan 2001 18:34:26 +0000

Ever wanted to see what your Haskell program is doing? 

Andy Gill's Hood library ( represents
a big improvement over previous uses of trace & co. It doesn't affect
strictness properties, and instead of displaying debug information
in the nearly incomprehensible order in which it is generated, it
collects, post-processes and pretty-prints the information and displays
the results after program evaluation, in a more readable form.

However, as Andy already noted in the Hood documentation, there is
a lot of useful information to be gathered from the order in which
(parts of) data structures are observed. Now that Hood associates
individual observation events with the data structures to which they 
belong, thus facilitating comprehension of observations, it would be 
nice to find a way to visualise the observation order as well. 

Andy's plan was to incorporate such a feature into a textual browser 
add-on for Hood (in CVS, not released yet?). But for tasks for which 
structural context and relationships between parts dominate over details, 
my personal preference would be a graphical form of visualisation. 

GHood is my current attempt to add a such a graphical viewer to Hood. 
It hasn't yet reached its final form, but it is quite useful and usable 
already. We have played with it locally, and I can't spent too much 
time on this, but I would like to get some external feedback before 
I finalise the development. Hence this pre-release.

Currently, GHood comes in two files: a drop-in replacement for the
Hugs98 variant of Hood (only minimal changes, same interface) and
a Java class file archive for the graphical viewer itself. 

To find the two files, please visit my Haskell corner at:

Enjoy (and let me know what you think about it),


Claus Reinke,
Computing Lab, University of Kent at Canterbury