Re: technology discussion → does the world need a "new" C ?

On Fri, 16 Aug 2024 01:08:15 +0100
Ben Bacarisse <ben@bsb.me.uk> wrote:

Bart <bc@freeuk.com> writes:
 

On 15/08/2024 15:33, Ben Bacarisse wrote: 

Bart <bc@freeuk.com> writes:
 

On 15/08/2024 09:43, Tim Rentsch wrote: 

Bart <bc@freeuk.com> writes: 

 

                          C call-by-value
call-by-reference ===============         =================
    at call:
>
      (array argument)    F(A)                    H(A)
>
      (pointer argument)  F(p)                    (disallowed) 

>
My posts were about passing *arrays* and the fact that C's
pass-by-value was remarkably similar to pass-by-reference. 

Which is why, presumably, you didn't show the differences.  Your
post was all polemic not part of a collegiate discussion of the
similarities and differences.
 

However your entry for pointers is not correct: 

No, the entry is correct.  H(p) would be (is?) disallowed when H's
parameter is a reference to an array. 

>
Sorry, what language does the right-hand column pertain to? /Any/
language that has call-by-reference, or Tim's hypthetical language?
 

 
Tim said that case was "disallowed".  You call that an error on his
part.  What language did you have in mind that permits such a gross
warping of types?  I would describe /any/ language that allowed it as
having a design error.
 

Or any that could be used to prove him right?
>
In general there is no reason, in a language with true
call-by-reference, why any parameter type T (which has the form U*,
a pointer to anything), cannot be passed by reference. It doesn't
matter whether U is an array type or not. 

 
I can't unravel this.  Take, as a concrete example, C++.  You can't
pass a pointer to function that takes an array passed by reference.
You can, of course, pass a pointer by reference, but that is neither
here nor there.
>

IMHO, C++ is a particularly bad example.
Yes, C++ has call-by-reference misfeature. But arrays in C++ are
2nd class citizen, same as in C. They can't be assigned and can't be
passed to callee, neither by value nor by reference.

Also, I suspect that if you ask Ken Thompson, he will tell you that C++
does not really have 'call by reference'. Instead, it has references as
1st class object, so, naturally, values of references can be used
during 'call by value'.
I have enough of respect to KT to consider that his POV is not a
nonsense.