On 16/08/2012, at 6:54 AM, dobesv wrote:
> Currently to map C++ methods to felix you cannot rely on the default template.
>
> The default template for C function bindings is something like "$0($a)"
> (where $0 is the name of the function).
>
> For methods it should be "$1->$0($a)" or "$1.$0($a)".
>
> Perhaps an adjective "method" on the function definition would cause it to
> use the latter form when no explicit template is provided.
There's a somewhat related set of issues here.
(1) At present you can make function like:
fun f: int -> int -> int -> int = "f($1,$2,$3)";
but it won't work as expected, f 1 will fail by generating
f(1,$2, $3)
or else give an error (not sure). And f 1 2 3 will fail
the same way, trying to apply
f(1,$2,$3) 2 3
I could hack this so it works. Making f 1 2 3 work
isn't so hard. Making f 1 work is a bit harder.
however Felix already automagically wraps
macros like
f: int->int = "$1";
into functions by
fun f_closure (x:int) => f x;
if you happen to try to use f as a closure, you actually
get f_closure.
note that
fun f: int * int -> int;
is a cheat. The f macro will NOT accept a tuple argument,
it accepts two arguments, but Felix maps a tuple into these
two arguments. If you actually wanted a single tuple argument
you have to write
fun f: int * int -> int = "f($t)";
(2) There is another problem for C++ bindings:
fun f: int -> int;
binds to "whatever f is in scope". If you want to bind to
::myspace::f
you have to write
fun f:int->int = "::myspace::f($a)";
This is not much of a problem for function but for types,
there's no way to do it:
cstruct X { x ; int; };
binds Felix X to whatever X is in scope. It isn't possible
to bind X to ::myspace::X other than by
type X = "::myspace::X";
and if you do that you lose the members.
(3) For class methods something like:
cclass X {
fun f: int -> int;
}
might make sense, this produces:
fun f: X * int -> int = "$1.f($2)";
fun f: &X * int -> int = "$1->f($2)";
however that's a bit sick, better would be:
fun f: X -> int -> int
which would also allow an object closure, as well has
handling both variables of type X and pointers &X.
The only problem is that
f object
would be ambiguous if there's more than one method named f.
If you do this in C++ or any other OO language .. you deserve what you get!
note you can already write:
struct X {
x : int;
fun add (y:int) => self.x+y;
}
in Felix, and
anX . add
is perfectly legitimate and forms an object closure. The actual signature
of add is:
fun add: X -> int -> int;
and the definition is:
fun f(self:X) (y:int) => self.x + y;
The transformation is done in the parser so there is no semantic impact.
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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