Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!pasteur!con.Berkeley.EDU!sarge
From: sarge@con.Berkeley.EDU (Steven Sargent)
Newsgroups: comp.lang.pascal
Subject: Re: Pascal User Manual and Report
Message-ID: <841@pasteur.Berkeley.Edu>
Date: 18 Feb 88 15:16:44 GMT
References: <169900010@uiucdcsb>
Sender: news@pasteur.Berkeley.Edu
Lines: 25

What do you mean by the "current definition?"  I know J&W leaves it
open, but who knows about ISO?   (Does anybody care?)  As to
implementations:

	VAX Pascal (on VMS) uses short-circuit evaluation;

	Sun Pascal (descendant of Berkeley pc) uses a compile-time
	flag, -P, to enable short-circuit evaluation (default full
	evaluation);

	SVS Pascal (Silicon Valley Software; makes compilers for
	various 68000, 32000 boxes running UNIX and other stuff)
	uses short-circuiting in conditionals, e.g.,
		if (p <> NIL) AND (p^.key <> key) then {don't explode}
	but full evaluation for assignments, e.g.,
		found := (p <> NIL) AND (p^.key = key);	{oops}

Coming from C-land, short-circuit evaluation seems much more natural
to me, so I don't mind that my compilers tend to use it.  But it is
bothersome that the behavior isn't nailed down more precisely.
For an allegedly portable language, Pascal leaves a lot of important
stuff to the discretion of implementors; this is just one fairly
minor, but insidious, example.

S.