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From: jeff@slovax.uucp
Newsgroups: comp.lang.c
Subject: Re: Two replacements for unary +
Message-ID: <7017@brl-adm.ARPA>
Date: Tue, 21-Apr-87 10:57:34 EST
Article-I.D.: brl-adm.7017
Posted: Tue Apr 21 10:57:34 1987
Date-Received: Wed, 22-Apr-87 03:20:40 EST
Sender: news@brl-adm.ARPA
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in article <489@danews.ATT.COM>, lvc@danews.ATT.COM (Larry Cipriani) says:
> I am very dissatisfied with unary plus in the ANSI C.
..
> The first is to use a special cast called (eval) (or
> some other appropriate word).  It would be used like this:
>
>     x = (eval)(a + b) + c;
>
> In this statement the sum 'a + b' would be computed first,
> then that would be added to 'c'.
>
>     x = (eval)(a * b) * (eval)(c * d)
>
> Here the products 'a * b' and 'c * d' would be computed,
> and then they would be multiplied together.  (messy huh?)
>
> Cast already has the correct precedence for this to
> work (no?).  Furthermore, casts are already in C language.
>
> Does anyone see a problem with this approach?
> Is associativity of cast a problem?

  I like this idea. For one, it deals with the context of the
expression, not the content. The purpose is to communicate to
the compiler that one portion of an expression should be
evaluated first. The unary '+' will do the same, but at the
expense of creating a compiler directive disguised as an operator.
All other arithmetic operators are subject to optimization.
Why not the unary '+' ??? Because it's a special case !!!

  The unary '+' is needed as just that -- the other half of
unary '-'. It should be subject to the same compiler interpretation.

if
  -( a - b ) + z
can become
  z + b - a            { evaluated left to right }
why can't
  +( a -b ) + z
become
  z + a - b            { evaluated left to right }
???

  Let's use compiler directives that are distinct from
arithmetic operators. It doesn't mess up the language with
special cases that confuse the novice and confound the
compiler writter.

Thanks for your time.

---------------- uw-beaver!tikal!slovax!jeff  (jeff loucks) -----------------
terrorist cryptography DES drugs cipher secret decode NSA CIA NRO IRS coke
crack pot LSD russian missile atom nuclear assassinate libyan RSA infiltrate
smuggle    (suck it up there NSA !!) (really now, is this any way to act ???)
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--
---------------- uw-beaver!tikal!slovax!jeff  (jeff loucks) -----------------
terrorist cryptography DES drugs cipher secret decode NSA CIA NRO IRS coke
crack pot LSD russian missile atom nuclear assassinate libyan RSA infiltrate
smuggle    (suck it up there NSA !!) (really now, is this any way to act ???)
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