questions about IF

[barmar@THINK.COM]

   Date: Fri, 10 Jun 88 14:03:06 EST
   From: bouma@purdue.edu

   I just noticed something strange about the Symbolic's IF:
   (I am still using 7.1 so this may not apply in 7.2?)

For compatibility reasons, it will probably remain forever.

   So the else-clause to an IF is an implicit PROGN.
   This is NOT in the Common-Lisp language specification?

It is a Symbolics extension to Common Lisp.  It was a documentation
error that this was not noted in the chapter on Common Lisp
compatibility.  I think this was fixed in the 7.2 documentation, but I
don't have it handy at the moment to check.

	Someone said recently in this group that IF is now a more primitive than
   the COND. Can I get more details on this? How could they have done this? Does
   my code run faster now if I use Ifs than if I use Conds?

I think you'll get equivalent (although not necessarily identical)
results whether you use nested IFs or a COND.