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From: jas@rtech.UUCP
Newsgroups: comp.lang.c
Subject: Re: Unary plus (and wysiwyg order or evaluation)
Message-ID: <752@rtech.UUCP>
Date: Fri, 10-Apr-87 12:52:50 EST
Article-I.D.: rtech.752
Posted: Fri Apr 10 12:52:50 1987
Date-Received: Sun, 12-Apr-87 01:30:59 EST
References: <6772@brl-adm.ARPA> <803@viper.UUCP>
Reply-To: jas@rtech.UUCP (Jim Shankland)
Organization: Relational Technology, Alameda CA
Lines: 37

Sorry to add to a discussion that may have gone on too long; I'll be brief.

Postings like this betray some confusion:

 >>>... it is not a _minor_ matter when something like the proposed unary
 >>>plus override on parenthesis evaluation order is added to a language.
 >>
 >>... I didn't even realize my parentheses weren't being honored.  Seriously.
 >
 > It wasn't until reading about unary '+' that i knew that C might
 > disregard my parens.

>I think parens should be followed without any micky-mousing from the compiler.

PARENTHESES AFFECT PRECEDENCE, NOT EVALUATION ORDER.  THESE ARE 2 DIFFERENT
THINGS.  To put it another way, parentheses affect the shape of the parse
tree for an expression; evaluation order is an order in which the parse
tree is walked.  Unary '+' does not "override" parentheses, nor may a compiler
"disregard my parens."  Parens have a precise and essential function, entirely
distinct from order of evaluation.

If you want to give the programmer some control over evaluation order (a
reasonable thing), some options for C are:

(1) Force the programmer to explicitly use temporaries (the current solution);
(2) Allow unary '+' as an order-of-evaluation directive (the ANSI C solution);
(3) Come up with some other syntax for order-of-evaluation directives.

People may argue over which of these options is most reasonable.
What is NOT reasonable is to use parentheses as an order-of-evaluation
directive.  They are already taken, for altering operator precedence.
Is the distinction really so difficult to understand?
-- 
Jim Shankland
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                  rtech!jas
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