Debugging Arrays

[Hal Daume III]

If you're willing to use something other than Hugs, you're set.  With GHC
or NHC you could use the HAT debugger (www.cs.york.ac.uk/fp/hat/).  Or
even just with GHC if you compile with -prof -auto-all (for profiling),
you can run with +RTS -xc to get a stack backtrace on errors.

Otherwise, if you import IOExts, you can get poor-man's tracing by doing
something like: assume your original function looked like:

myfunc a b c = d
myfunc e f g = h

you could change this to:

myfunc a b c | trace ("entered myfunc " ++ show (a,b,c)) False = undefined
myfunc a b c = d
myfunc e f g = h

then you'll get these traces printed (of course you only show arguments
which are showable).

HTH

 - Hal

--
Hal Daume III

 "Computer science is no more about computers    | hdaume@isi.edu
  than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

On Wed, 8 Jan 2003, Matthew Donadio wrote:

> Hi all,
> 
> I am having a tough time debugging an array problem, and I was wondering
> if anyone had some pointers.
> 
> I am working on a complicated function that relies on a few mutually
> recursive arrays (AR parameter estimation using Burg's Method).  I am
> getting a runtime error, index: Index out of range, when I test out the
> function.  For the life of me, I cannot figure out where the error is. 
> One complication is that not all of the arrays elements are defined for
> the index bounds.
> 
> I have tried several simplifications to isolate the arrays, but when I
> simplify too far, I run into type problems.  Is there an easy way to
> trace execution?  Does anyone have any advice on how to go about
> debugging this?
> 
> I am using Hugs 98, November 2002 if it matters.
> 
> Thanks.
> 
> -- 
> Matthew Donadio (m.p.donadio@ieee.org)
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