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From: root@sdd.UUCP (Root)
Newsgroups: comp.lang.c
Subject: Re: short circuit evaluation
Message-ID: <379@sdd.UUCP>
Date: Sat, 7-Mar-87 12:51:58 EST
Article-I.D.: sdd.379
Posted: Sat Mar  7 12:51:58 1987
Date-Received: Mon, 9-Mar-87 19:03:05 EST
References: <844@wanginst.EDU> <4700004@uiucdcsm> <4211@utcsri.UUCP> <609@viper.UUCP>
Reply-To: root@sdd.UUCP (Root)
Organization: Software Design & Development Corp, Camarillo, CA
Lines: 37

In article <609@viper.UUCP> john@viper.UUCP (John Stanley) writes:
>
>If you have three expressions:
>	1:  a+b+c
>	2: (a+b)+c
>	3:  a+(b+c)
>all three of them should not be evaluated the same way.  Greg implys that
>they should be.  This is not so.  When an equation contains '(' and ')'
>it intentionaly (and explicitly) defines the parse tree structure that will
>result.  The statement "redundant ()'s grow in C like mushrooms" may be true,
>but it doesn't give anyone the right to arbitrarily ignore explicit cues
>to the compiler.  When I don't care, I don't use them.  When I do, I do
>so for a reason..........

	NO!!!!  The new DRAFT ANSI standard explicitly says:

	"An expression involving more than one occurance of the same cummutative
	and associtive binary operator (*, +, &, ^, |) may be regrouped 
	arbitrarily, EVEN IN THE PRESENCE OF PARENTHESES, provided the types of
	the operands or of the results are not changed by this regrouping.  To
	force a particular grouping of operations, either the value of the
	expression to be grouped may be explicitly assigned to an object, or
	grouping parentheses may be preceded by a unary plus operator."


Therefore if one desires to explicitly specify an order, in the new ANSI
standard one can use a unary plus operator as follows:

	1:	+(a + b) + c
	2:	a + (+(a + b))

This should guarantee the evaluation order!

									Daniel Corbett
									Software Design & Development Corp
									360 Mobil, Suite 103
									Camarillo, CA 93010