Function Pointer Syntax for Whiley

One of the next big issues needing to be addressed is the syntax for [[function pointers|function and method pointers]].  The syntax I’m thinking of is close to that used in C and C++ (see e.g. here and here).  My initial idea results in something like this:

define MyComparator as {
    int compareTo(MyRecord,MyRecord)
}

This is defining a record type, MyComparator, which contains a single field, compareTo. This field is, of course, a function pointer accept two MyRecord‘s and returning an int. We can invoke it like so:

int f(MyComparator comp, MyRecord r1, MyRecord r2):
    return comp.compareTo(r1,r2)

Similarly, we can “take the address” of a function using the & operator like so:

int comp(MyRecord r1, MyRecord r2):
    ...
    return 1 // positive case

void System::main([string] args):
    r1 = ...
    r2 = ...
    x = f(&comp,r1,r2)

At this point, the syntax seems a little inconsistent.  I’m using & from C/C++, but not requring a * and/or allowing ->. Following C/C++ syntax properly would require something like this:

define MyComparator as {
    int (*compareTo)(MyRecord,MyRecord)
}

int f(MyComparator comp, MyRecord r1, MyRecord r2):
    return *(comp.compareTo)(r1,r2)

To me, this is ugly and unnecessary. On the other hand, perhaps I should consider dropping the & so everything is consistent. E.g. by permitting this

void System::main([string] args):
    r1 = ...
    r2 = ...
    x = f(comp,r1,r2)

This could work, for sure … But, somehow I’m not a great fan.

Processes

Processes and methods present their own problem. Consider this example:

define Writer as process {
 int Writer::write([byte] bytes)
}

This declares a process type, Writer, which has one field, write. In this case, write is a method pointer, as indicated by the :: in the above. It seems redundant to require Writer::write, but it’s necessary since write could be a method pointer to some other kind of process. This can be slightly improved by allowing a short-hand like this:

define Writer as process {
 int ::write([byte] bytes)
}

And, in fact, I want to go further a permit this equivalent short-hand notation:

process Writer {
 int ::write([byte] bytes)
}

But, somehow, this doesn’t sit quite right for me. I suppose I need to ponder some other options …

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