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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Difference between these pointer syntaxes
Date: Tue, 16 Aug 2016 15:22:29 -0700
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supercat@casperkitty.com writes:
> On Tuesday, August 16, 2016 at 2:47:00 PM UTC-5, Keith Thompson wrote:
>>     What is sometimes called "rvalue" is in this International Standard
>>     described as the "value of an expression".
>
> The Standard may have chosen to ignore the term "rvalue", but it describes
> a concept which cannot I think be accurately summed up in the phrase used
> by the Standard, though perhaps "evaluated value of an expression" might be
> appropriate.
>
>     int myArray[3] = {1,2,3};
>     char *p = (char*)&(myArray[1]);
>
> upon what does the operator "&" act?  From what I can tell, it acts upon
> the expression "myArray[5]".  Does that expression have a value?  I would
> say that it does--the value is 2.  Does that mean that the expression is
> an rvalue?  Not as other documents use the term, because it isn't evaluated.
> On the other hand, rather than use the phrase "evaluated value of an
> expression" all the time, it might be easier to simply define the term
> "rvalue" once and then use that.

The way C uses the term (again, only in a footnote), an "rvalue"
cannot be an expression.  An "rvalue" is a *value* that results,
at run time, from evaluating an expression.

On the other hand, an "lvalue" as defined by the C standard is a
kind of expression.  (This is, as I understand it, different
from the original meaning of the term.)

In `&(myArray[1])`, the `&` operator is applied to the expression
`(myArray[1])`, which is an lvalue.  The value contained in
`myArray[1]` (which happens to be 2) is not relevant, since no
*lvalue conversion* takes place.

I don't know what point you're trying to make.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"