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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 11:35:35 +0100
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On 29/08/2024 00:43, Ben Bacarisse wrote:
> Bart <bc@freeuk.com> writes:
> 
>> On 28/08/2024 15:57, Ben Bacarisse wrote:
>>> Bart <bc@freeuk.com> writes:
>>>
>>>> On 28/08/2024 00:49, Ben Bacarisse wrote:
>>>
>>>>> Indeed, and BLISS is not like that.  I had hoped to shed some light on
>>>>> why there is some logic to BLISS's rather idiosyncratic design.
>>>>>
>>>>>> Given a declaration like 'int A' then:
>>>>>>
>>>>>>                               BLISS   C
>>>>>>
>>>>>> Read or write A's value   .A       A
>>>>> I don't think that's right.  To change the value at address A (what I
>>>>> think you mean by "write A's value") you write
>>>>>      A = 42;
>>>>> in BLISS.  And to add one to the value at address A you write
>>>>>      A = .A + 1;
>>>>
>>>> OK. That's just makes it more bizarre than I'd thought.
>>> Curious.  It's what makes it consistent, though it is definitely an
>>> uncommon approach.
>>>
>>>> The example I saw
>>>> included these lines:
>>>>
>>>>       GETNUM(X);            ! returns a value via X
>>>>       Y = STEP(.X);
>>>>       PUTNUM(.Y)
>>>>
>>>> So in an rvalue context:  X reads its address; while .X reads its
>>>> value.
>>> The whole point is to remove the two contexts.  A variable name is
>>> /always/ an lvalue (which is why it can be assigned).  C has an implicit
>>> lvalue to rvalue conversion in the contexts you have come to expect it.
>>> BLISS does not.  You always need a dot to convert to an rvalue.
>>
>> This is the kind of thing I meant a few posts back. You don't need to take
>> A (which refers to some place where you can store values), and tell it to
>> fetch that value. Most HLLs will do that without being told.
>>
>> (My point was that that was a distinguishing feature of HLLs, which is
>> missing in Forth for example.)
> 
> We are talking at cross purposes then.  I was not addressing anything
> about your view of what makes an HLL.
> 
>>>> But in an lvalue one:     Y writes its value; .Y may not be defined
>>>>
>>>> It looks asymmetric. C like most languages is symmetric, you write 'A = A'
>>>> with the same syntax on both sides.
>>> Since assignment is inherently asymmetric (you can't write 3 = A but you
>>> can write A = 3) C's syntactic symmetry hides a semantic difference.
>>> What is needed on the two sides is not the same.
>>
>> I would argue that it is exactly the same.
> 
> How do you argue that, given that A=3 is allowed and 3=A is not?

I explained that. LHS and RHS can be identical terms for assignment in 
pretty much every aspect, but there are extra constraints on the LHS.

In the case of :

    (c?a:b) = (z?x:y);

C won't allow it, but some other languages will.

Remember that the programmer can only express their intentions in the 
form of syntax.

> ...
>>>> I assume that in BLISS, A = A is legal, but does something odd like copy
>>>> A's address into itself.
>>> What's odd about that?  And why call is a copy operation?  Do you think
>>> of A = 42 as a copy operation?  BLISS is a low-level system language.
>>
>> Why do you mean by call?
> 
> Typo.  I meant to write... And why call /it/ a copy-operation?  Do you
> think of A = 42 as a copy operation?

If '=' means assignment, then what else is it?

Depending on language, it might be shallow, or deep, or something 
depending how it works or what is being assigned.

According to Wikipedia:

"In computer programming, an assignment statement sets and/or re-sets 
the value stored in the storage location(s) denoted by a variable name; 
in other words, it COPIES a value into the variable"

(My emphasis.)

I don't know why you're always so contradictory. Is it a game trying to 
catch me out on some pendanty? It seems to be popular here.

This subthread started with me asking which HLL goes between Assembly 
and C, if C was supposedly mid-level. I don't know how it got on 
discussing what exactly assignment means.