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

On 10/07/2024 00:50, Keith Thompson wrote:

bart <bc@freeuk.com> writes:
[...]

Arrays can be passed by explicit reference:
>
   void F(int(*A)[20]) {
       printf("%zu\n", sizeof(*A)/sizeof((*A)[0]));    // shows 20
   }
>
That can be called like this:
>
   int a[20];
   F(&a);

 On the language level, that's passing a pointer to an array object.
The pointer itself is passed by value.  Passing a pointer to an array
is conceptually no different than passing a pointer to anything else.

I was replying to:
  "In C, arrays are not passed to functions, period."

C has pass-by-reference in exactly the same way that it has
linked lists.  It has neither as a language feature, but both can
be emulated using pointers.  And you can't really understand how
C handles arrays if you start by asserting that they're "passed
by reference".

This is how I can pass arrays by reference in my language:
    proc F([]int &A) =
        A[2]:=777
    end
    proc main=
        static[]int A = (10,20,30)
        println A[2]            # shows 20
        F(A)
        println A[2]            # shows 777
    end
Without the feature I'd need to use 'ref[]int A' and call as F(&A) (the extra deref inside F is added by the commpiler).
This is how you might do the same thing in C:
   void F(int A[]) {
       A[1]=777;
   }
   int main(void) {
       int A[] = {10,20,30};
       printf("%d\n", A[1]);       // shows 20
       F(A);
       printf("%d\n", A[1]);       // shows 777
   }
To get the 777 output involves somehow passing the array by reference.
But notice how C gives exactly the same result as my code that used by-reference, even though:
  * C "doesn't pass arrays by reference"
  * C's F function uses the same parameter type (only & is missing; maybe
    by-ref is implicit...)
  * No explicit de-ref is needed inside F
  * No explicit address-of is needed when calling F
So C behaves exactly as though it passes arrays by-reference, and yet it doesn't have pass-by-reference. In fact, C does it without even needing to be told!