This program demonstrates conditions and restarts. It's uses the
Common-Dylan library. Harlequin users should substitute the Harlequin-Dylan
library and d2c users should upgrade to the latest CVS version. Mindy users
should volunteer to help me implement Common-Dylan for Mindy.

I've appended my info-dylan message describing this program.

Cheers,
Eric

--- info-dylan message
On Tue, Apr 13, 1999 at 06:01:25PM +0000, Michael T. Richter wrote:
> I'm afraid that I'm more interested in the practical side of things than
> the theoretical.  I understand the model, I think, (especially now that
> you've done the excellent summary) but cannot for the life of me
> translate this into code.  This is why I was asking if there was source
> code someone could point to so I could see how the individual pieces fit
> together in terms of actual typing.

OK, I need to write some test code for this feature, anyway. I've appended
a program which produces the following output:

  $ restart-example goodfile1 goodfile2 goodfile3
  Processing file 'goodfile1'.
  Processing file 'goodfile2'.
  Processing file 'goodfile3'.

  $ restart-example badfile1
  Cannot find the file 'badfile1'.
  Alternate file (RETURN for none): goodfile1
  Processing file 'goodfile1'.

  $ restart-example badfile1
  Cannot find the file 'badfile1'.
  Alternate file (RETURN for none): badfile2
  Cannot find the file 'badfile2'.
  Alternate file (RETURN for none): goodfile1
  Processing file 'goodfile1'.

  $ restart-example badfile1
  Cannot find the file 'badfile1'.
  Alternate file (RETURN for none): 
  Processing aborted because the file 'badfile1' could not be found.

This program shows how to design and document a restart protocol, implement
condition handlers, perform non-local exits, and do all sorts of fun Dylan
tricks. The processing code is completely separate from the user-interface
code, too, thanks to the use of <restart>s.

This program also shows off a tiny fraction of what Dylan can do. If most
of your experience involves C++ or Java, you may have to bend your mind a
bit. Please don't hesitate to ask questions if something seems confusing.

> >Dylan's actually about four times as powerful as it appears. :-)
> 
> That's about right from my tinkering.  There are an awful lot of Deep Magic
> concepts in this deceptively small language.

Yup. Dylan's a Trojan horse, of sorts. You can begin by using it as a
straightfoward, object-oriented language with some neat libraries. But if
you use it some more, you'll discover that Dylan has a tiny core which is
very powerful.

> And I haven't even really done any digging at macros yet (beyond using the
> standard ones, natch)....

Ah, that's a problem for another day. :-) For now, poke around at the
attached program.

Cheers,
Eric