Any documentation on exception?

[briangmilnes]

Goofing around with test units, I quickly realized there is not much on exceptions
in the book or the wiki. Which took a bit of time to suss out.

Did I miss anything?
If not should I write up a subsection for somewhere in the book?
Two things I could not suss out is to_string for a general exception
and do they get line numbers? I would guess neither exist in a research tool.

[briangmilnes]

Okay, I've worked through a set of exception examples, and it's as I expected.
I can describe what they are, how to specify them, how to raise them, how to catch them in a try.
And even that one can reraise one.
And that the type system won't let you raise one to the top level.
So I tested a top level loop that catches an exception and exits.

The only things that I don't know how to handle are:

1. the compiler uses OCaml Printex internally to print arbitrary exceptions.
   The code generation does not emit this, so we can not use it at runtime.
   I don't think it's necessary at this stage, just a sentence that describes this.
2. I did try typeclasses for this but could not seem to make that work. If I have missed something, kindly chime in.
   I'll write a pretty standard description of exceptions in prose, run it by someone, and typeset it.