Re: Top 10 most common hard skills listed on resumes...

Bart <bc@freeuk.com> writes:

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.

So you use "exactly the same" to mean "exactly the same except for the
differences".  I don't think this point needs any more discussion, do
you?

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?

That's was my question.  You called it (in BLISS) a "copy" operation.
Why did you use that term rather than just saying that "A = A assigns
that address of A to the location A".  I'm trying to find out if your
use of the word copy rather than assign is interesting in some way.

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.

I wanted to explain how BLISS gets rid of the lvalue/rvalue distinction
because you seemed to have misunderstood it.

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.

Because, unlike you, I want to understand you before commenting.  It was
a trivial question (made more complex by a typo if mine, for which I'm
sorry).  You found BLISS's meaning of A = A to be "odd" and you
explained the "odd" by using the word "copy" rather than "assigns".  I
just wanted to know if there was more behind your use of the word.

I don't think there is anything that needs further explanation because I
think you just said "copy" when "assigns" would have done.

--
Ben.