[Hat] Program Compiles With GHC 6.6 but not Hat

[Neil Mitchell]

Hi Tom,

> These assessments depend very much on your point of view.

With infinite resources I'm sure all these things would get fixed.
Unfortunately infinite resources is not something Hat has... Without
infinite resources, you have to prioritise. If Hat was being developed
by a commercial company, I am sure more focus would be directed
towards graphical tools and fixing the small issues to give something
more polished. Unfortunately in academia those things won't make a
paper, win any research grants, and are harder to get done.

That fact that the goal posts for Haskell keep getting moved also
makes this a much harder task!

> and
> there were 3 different idiosyncrasies of hat which gave problems.  The
> defaulting idiosyncrasy was one of them.

Please list all 3 of them.

> I imagine that most people that
> try hat find it won't understand their code, and give up on it
> immediately.  I am therefore skeptical that this is hardly ever a problem
> for people even if you 'hardly ever come across' it.

I don't use Hat because every time I've tried to use it I get to the
point where it's easier to insert trace calls than work round whatever
particular reason Hat is failing for now.


> I recently gave a presentation about haskell at my work, and had to
> significantly tone-down the strength of my recommendation of it because I
> find haskell code so difficult to debug.  At work we use windows (as I do
> at home), and despite Neil Mitchell's efforts, not enough of the hat tools
> have been converted to windows to make it worth using them.

If the Hat tools all worked on Windows, would that change your
assessment of Hat? Would that convince you to use it? Because I don't
use Hat, that makes me less inclined to spend too much effort porting
the tools. Personally, even with all the tools available on Windows, I
still wouldn't use Hat because of the unreliability of generating
traces.

> I didn't find
> the instructions for using hat via cygwin sufficient for someone with my
> low level of expertise.

If debugging Haskell is to painful as to have to use cygwin, just
rewrite your application in C# and use the great debugger included
with Visual Studio :)


> I have no idea how difficult it would be to make hat work on all valid
> haskell98 code 'out of the box', on windows as well as unix, so I can't
> criticize anyone for the fact that it doesn't.  However, I am strongly
> opposed the point of view that, for whatever reason, this doesn't really
> matter.

I have a plan to get this going using Yhc.Core. The problem would be
that its a different version of the code, based on your original, but
the user would have to brain hop between their original code and the
code being debugged. Having worked with Yhc.Core plenty, my brain does
this hopping automatically, but I suspect that it won't be fun for
other people - but should be very reliable.

Thanks

Neil