[MLton] Callback to function pointer?
Wed, 13 Jul 2005 09:08:03 -0400 (EDT)
> > MLton.Pointer.t is the only reasonable "expandOpaque" primitive
> > type, but it can still be useful to import an address at an opaque
> > SML type.
> Makes sense. I slightly lean toward _address (with the type
> annotation) over "_import #" or "_import &". But only slightly.
For FFI _import, we currently have the following:
(* A. fetch a simple FFI object (when evaluated) *)
_import "name" : ffiTy;
(* B. call a function FFI object (when applied) *)
_import "name" : argTy -> resTy;
(* C. address of an FFI object (when evaluated) *)
_import # "name" : ptrTy;
(* D. call a function through a pointer (when applied) *)
_import * : ptrTy -> (argTy -> resTy);
I'm open to suggestions for better names or syntax. There is a suggestion
to replace C with
_address "name" : ptrTy;
It does appear that there is a significant difference between A and B/D
and I wonder if that is worth making explicit by a different syntax.
Some other things of note: C and D parse into distinct AST nodes, while
A/B parse into the same AST node. Hence, the elaborator needs to check
whether the expanded type annotation is an arrow to determine how to treat
an A/B import AST node.