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

On 2024-08-15, Bart <bc@freeuk.com> wrote:

On 15/08/2024 22:36, Tim Rentsch wrote:

I see.  So your point is, if we ignore all the ways that the two
modes are different then they are exactly the same.
 
Brilliant deduction, Dr. Watson.

>
So your approach is to totally ignore all the ways that the two modes
are identical.

Almost any two different things have some attributes that are identical.
If we consider a bicycle and a fish, we can probably come up with common
attributes.

Passing pointers by value similar to call-by-reference, but also
different.

The program can calculate a bad pointer and pass that by value.

Call-by-reference implementations can take measures to ensure that
a a bad reference is not passed.

The function call syntax itself, for a by-reference parameter, requires
an expression that designates an object, and takes a reference to that
object implicitly. Inside the function, there is no visible pointer;
the by-reference argument appears to be an alias for the referenced
object. Since there is no pointer, the address cannot be incremented
or reassigned.

(In a language that has both pointers and call-by-reference, it may
be possible to calculate a bad pointer, dereference it and use the
resulting expression as a reference argument. Then the reference
will be bad: but the root cause is pointer misuse, not the
call-by-reference mechanism.)

It is mainly syntactic differences. Call-by-reference can be implemented
using pointers, which can happen in a very early compiler pass; the
first intermediate code can already be transformed to using pointers.

If your point of view is that pointers are what is "real under the
hood", then call-by-reference is just "syntactic sugar" for pointers.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca