I do not recall whether I have talked about this before on the list.
I want to introduce a new function-like type into BitC: the method. A
method is a function associated with a structure type that does not
occupy storage within structure instances. Given:
(defstruct (S 'a 'b) :val
int32 i;
m: (method 'a -> 'b))
(define (S.m (by-ref S 'a 'b) 'a -> 'b)
.. body of method ..)
[ First argument is by-ref if the structure type is :val. If the
structure type is :ref, then it would simply be (S 'a 'b) ]
the application:
(let ((s-inst (S int32 char)))
(s-inst.m 3 #\c))
is conceptually equivalent to:
(S.m s-inst 3 #\c)
or it would be, if this were syntactically expressible.
If S is a :ref type, we can then introduce "make-thunk":
make-thunk: (fn inst:S meth:(S::method 'a -> 'b) -> (fn 'a -> 'b))
which is basically how the current procedure constructor works. It
creates a heap-allocated code block that can later be invoked to inject
a reference to S that the receiving procedure can receive.
Note that since methods have no slots they are not assignable.
Note further that a procedure object (up to information hiding) can be
implemented as a structure with a single distinguished method _fn.
So far, there is nothing novel or interesting here. The fun part comes
in the next message.
shap
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