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Date: 7 Apr 93 22:58:57 GMT
From: agate!dog.ee.lbl.gov!network.ucsd.edu!ogicse!verdix!mark@ucbvax.Berkeley.
EDU  (Mark Lundquist)
Subject: Re: and then
Message-ID: <9560@verdix.verdix.com>
List-Id: <comp.lang.ada>

In article <1993Apr7.173556.17184@sei.cmu.edu> ae@sei.cmu.edu (Arthur Evans) wr
ites:
>In connection with a discussion of Ada's short-circuit control forms,
>sampson@nosc.mil (Charles H. Sampson) says
    Ada compiler writers appear to have abdicated their responsibility
    and make no attempt to determine when boolean operations can be
    optimized as short-circuit.

  Well, I'm not surprised that they make no such attempt, but it's not
  because they have abdicated any responsibility.  ARM 4.5(5) says of
  expressions involving 'and' and 'or':
     The operands ... are evaluated in some order that is not defined by
     the language (but before application of the corresponding operator).
  In other words, both operands MUST be evaluated.  That requirement is
  not unreasonable given the availability of the short-circuit forms.
>
 

I don't think it means anything MUST be evaluated.  If you write

	if TRUE and TRUE then
		do_something;
	end if;

are you saying the RM says that code must be generated to evaluate
the operands and apply the operator?

The RM is not talking about implementation, it is specifying the
*logical* semantics of these operators.