The first case of typeclasses now works:
//------------------------
#import <flx.flxh>
proc pr[t]:t="std::cout<<$1<<std::endl;" requires iostream;
typeclass Eq[t,u] {
virtual fun eq: t * u -> 2;
virtual proc ppp: t;
}
instance Eq[int,int] {
fun eq: int * int -> 2 = "$1==$2";
proc ppp (x:int) { pr x; }
fun fred: int -> int = "";
}
instance Eq[long,int] {
fun eq: long * int -> 2 = "$1==$2";
proc ppp (x:long) { pr x; }
}
fun jeq[r,s with Eq[r,s]] (x:r,y:s)=> x == y;
fun keq[t with Eq[t,t]] (x:t,y:t)=> jeq(x,y);
fun peq[t with Eq[t,t]] (x:t,y:t)=> keq(x,y);
proc zzz[t with Eq[t,t]] (x:t) { ppp x; }
pr$ peq$ 1,2;
pr$ peq$ 1,1;
zzz 1;
//----------------------------
There are some constraints, and some stuff which isn't
finished and heaps which isn't tested.
Typeclasses and instances have to be toplevel: that is,
they can be nested in modules but NOT in functions.
Instances must ground typeclass type variables: they
cannot be polymorphic (the methods can be .. they
can have extra type variables .. though this is not tested
yet and probably won't work)
You may not provide more than one instance for the
same grounding of type variables.
Typeclasses may only contain virtual functions and
virtual procedures.
Instances must instantiate these virtuals. They can
also contain extra functions, which can be helper
functions -- such functions are NOT available to
the typeclass client, they're private implementation
details of the instance.
At the moment, overloading doesn't work and the
instance checker only checks some virtual 'eq'
has an instance .. it doesn't check the type
of the instance is correct yet :)
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
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