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

On 16/08/2024 10:38, Michael S wrote:

On Fri, 16 Aug 2024 02:18:15 -0700
Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
 

Michael S <already5chosen@yahoo.com> writes:
[...]

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.

>
Is that an attempt at proof by authority?

 Yes!
 

Not only does Ken Thompson
have very little to do with C++, but you're basing your conclusion on
what you *suspect* he would say.
>

 Yes, but it's not baseless.
It is based on following section Go language FAQs that I assumed to be
either authored or approved by KT.
https://go.dev/doc/faq#pass_by_value

This seems to about what happens when a language has complex, two-level types where you have a descriptor, which has a pointer to the actual data.
The user may not be aware of that, and may think that passing such an object 'by-value' will copy the data. If the language only does 'shallow' pass-by-value as seems to happen here, there may be some pass-by-reference semantics.
This can get confusing. However, whatever the machinations of a particular type, if a language offers *explicit* pass-by-reference, then you will always be able to provide real pass-by-reference on top.
So in the case of those descriptors, it will pass a reference to the descriptor. This allows a caller to modify what's in the descriptor, and have that change visible in the caller.
(My dynamic language has some 3-level types! There, reference parameters make a tangible difference.)