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From: Bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: Top 10 most common hard skills listed on resumes...
Date: Thu, 29 Aug 2024 22:29:39 +0100
Organization: A noiseless patient Spider
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On 29/08/2024 21:30, Keith Thompson wrote:
> Bart <bc@freeuk.com> writes:
> [...]
>> So what exactly is different about the LHS and RHS here:
>>
>>     A = A;
> 
> The RHS is evaluated to determine the current value stored in the object
> named A.  The LHS is evaluated to determine the object that's designated
> by the name A; its current value is irrelevant.

Sure, but the same thing happens on both sides: one ends up performing a 
Read via that Lvalue, and the other does a Write via that Lvalue.

> In C terms, the RHS undergoes *lvalue conversion*, where an expression
> that's an lvalue is converted to the value stored in the designated
> object.  The LHS does not undergo lvalue conversion.
> 
>> (In BLISS, doing the same thing requires 'A = .A' AIUI; while 'A = A'
>> is also valid, there is a hidden mismatch in indirection levels
>> between left and right. It is asymmetric while in C it is symmetric,
>> although seem to disagree on that latter point.)
> 
> Because BLISS, unlike C, does not have implicit lvalue conversion; the
> prefix "." operator performs explicit lvalue conversion.  I presume the
> "." operator isn't specific to assignments.

But it must have that conversion on the LHS, otherwise it's A's address 
that is written to rather than its value, which doesn't make sense. 
That's why I said it was asymmetric; the RHS needs an explicit operator, 
the LHS doesn't.

I'd initially thought that both sides needed it.

> In C, the LHS and RHS are evaluated differently.  In BLISS, they're
> evaluated in the same way, requiring an explicit operator to do what
> done implicitly by context in C.  I'd call the former asymmetric and the
> latter symmetric.

It sounds like you've got it backwards.

How can A = B be asymmetric, but A = .B be symmetric?

Lots of people like to be contrary in this group!