Hi,

  I'm glad that there's interest for a tool like hat-anim.  I should
warn you however that the current version is far from perfect - it has
some problems with displaying infinite lists and with some lambda
expressions and worst of all has a pretty nasty memory leek problem
(there's what I get for writing it in C).  I am currently re-writing
it in Haskell, and hopefully will produce a more reliable tool.  I'll
tell you when the tool is working.


Thanks


Tom Davie


On 12 Oct 2004, at 14:34, Olaf Chitil wrote:


<excerpt>

<bold><color><param>0000,0000,0000</param>

From: </color></bold>Colin Runciman <<colin@cs.york.ac.uk>

<bold><color><param>0000,0000,0000</param>Date: </color></bold>11
October 2004 10:38:21 BST

<bold><color><param>0000,0000,0000</param>To: </color></bold>Philip
Wadler <<wadler@inf.ed.ac.uk>

<bold><color><param>0000,0000,0000</param>Cc: </color></bold>John
Hughes <<rjmh@cs.chalmers.se>, haskell@haskell.org, Simon Thompson
<<S.J.Thompson@kent.ac.uk>,  Susan Eisenbach <<sue@doc.ic.ac.uk>

<bold><color><param>0000,0000,0000</param>Subject: </color>[Haskell]
Re: elementary tracing for Haskell

</bold>


Phil,


<excerpt>Are there any tools for beginning programmers that give
traces of Haskell programs?  I want something like the following. 
Given the defintion


    sum [] = 0

    sum (x:xs) = x + sum xs


typing


    sum [1,2,3]


should yield this trace


    sum [1,2,3]

    1 + sum [2,3]

    1 + 2 + sum [3]

    1 + 2 + 3 + sum []

    1 + 2 + 3 + 0

    1 + 2 + 3

    1 + 5

    6


I know there are advanced tools like Hat, but (unless I'm missing
something) they don't yield anything as naive as the above, and it's
naive users I'm trying to help here.  -- P

</excerpt>

There is a Hat tool called hat-anim that can do this kind of thing. 
It was developed by Tom Davie as a student project.  It is not part of
the current "official release" of Hat but is included in the CVS
version.  Tom is now a PhD student at Canterbury (tatd2@kent.ac.uk),
supervised by Olaf Chitil (O.Chitil@kent.ac.uk).


Regards

Colin R



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</excerpt>