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

Bart <bc@freeuk.com> writes:

[on comparing array arguments in C with call-by-reference]

[...] the differences [between C rules and true call-by-reference]
can be summarised here;  [...]
>
                                 Call     Array access in callee
>
    C call-by-value              F(A)     A[i]
>
    true call-by-reference       H(A)     A[i]
>
What the user has to write is what's important, and here it is clear
that they write the same thing [in the two cases shown].

The comparison above is misleading because it is incomplete.
Let's compare the two modes more fully:


                        C call-by-value         call-by-reference
                        ===============         =================
  at call:

    (array argument)    F(A)                    H(A)

    (pointer argument)  F(p)                    (disallowed)

    (null argument)     F(0)                    (disallowed)


  inside function:

    (access)            A[i]                    A[i]

    (update)            A[i] = ...              A[i] = ...

    sizeof A            (pointer size)          (array size)

    A++                 (changes A variable)    (disallowed)

    A = (new value)     (changes A variable)    (disallowed)


The more complete comparion illustrate why C semantics should not
be thought of as call-by-reference.