Re: Named arguments in C

On 2024-07-04, Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:

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

It really needs language support. That has been done in C for
designated initialisers; named args are a similar feature, easier to
implement (they can only be one level deep for example) and IMO far
more useful.
>
Although there are a few extra problems with C because the extra info
needed (parameter names and default values) can appear in both the
definition, and any number of prototype declarations, which cannot in
conflict.

>
As I recall, we had this discussion here a while ago.  The fact that C
allows parameter names for a function definition to differ from those in
corresponding declarations is a bit inconvenient.  But what I recall
suggesting at the time is that the parameter names in a call need to be
consistent with the names in the visible declaration.
>
    void foo(int x, int y) {
        // ...
    }
>
    void foo(int xx, int yy);
>
    foo(xx: 10, yy: 20);

void (*pfoo)(int y, int x) = foo;

pfoo(xx: 10, yy: 20); // oops, arguments are silently reversed

Before we have named arguments, we have to somehow make name part of the
type, so that the above pointer initialization violates a constraint.

Problem:

   void foo(int, int);

   void (*foo1)(int y, int x) = foo;

   void (*foo2)(int x, int y) = foo;

The crux is that parameters/arguments which are /simultaneously/ named /and/
positional are a bad idea.

Keyword parmeters should be a separate new category, specially
declared, and understood not to be ordered. There should be no way
to pass by-order arguments to keyword parameters.

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