[MLton] MLton HOL

[Stephen Weeks]

> Unfortunately debugging the MLton HOL programs is hard, and I'm often 
> reduced to feeding in prefixes of the program to see if they produce 
> the same error :-( 

Are you aware of "-exn-history true"?  This might help, since the top
level handler will at least then display where the exception was
raised.

> The exception HOL_ERR contains useful debugging information, but
> since I don't know where it's being raise I can't wrap the correct
> function in an exception handler.
>
> I don't suppose it would be possible for ask MLton to print more than 
> just "unhandled exception: x"?

This gives me an idea for a pretty easy improvement to MLton.  We
could add

	val MLton.Exn.addTopLevelPrinter: (exn -> string option) -> unit

This would let you add your own exn pretty printers to the top level
handler.