Message-Id: <9211251741.AA23866@Athena.MIT.EDU>
To: aybee@Athena.MIT.EDU
Cc: jud@ithake.MIT.EDU
Subject: IsInteger
Date: Wed, 25 Nov 92 12:44:21 -0500
From: Judson Harward <jud%ithake@ceci.mit.edu>

	Good question.  It amounts to saying can you query the type
of any variable, doesn't it?  Where would you store the type
information?  In the list or with the variable?  If it is in the list,
we have a problem writing the expression evaluator.  first() should return
the base type, and by the time the base type is returned, all connection with
the list has been dissolved.  OR, our expression evaluator has to use
a kind of look ahead.  Ugly.  So, if we store it with the variable, then
we can query the type of everything.  Can we afford the overhead.  I am
open, but now is the time to decide, because the implementation
trade offs are significant.  I am tempted to say no, you can.

	A possible compromise:  Have builtins firsttype(), ithtype(),
that take a list as an argument and return the type.

	When we next meet, I think we should make a list of the BIG ISSUES
remaining with examples that indicate why they are significant.  Then draw up
a memo with pros and cons for each point and circulate it.  Start thinking
about what those issues are and so will I.

						Jud