[bitc-dev] constraining bitc's type system

[Swaroop Sridhar]

Sam Mason wrote:
> The main thing I was thinking of originally was being able to have some
> sort of structure like:
> 
>   (defstruct (foo 'a)
>     x:bool
>     y:int32
>     z:'a
>     p:(foo 'a))
> 
> and being able to know that if I have a function like:
> 
>   (define (fn foo:(forall ((refType 'a)) (foo 'a)))
>     (if (foo.x)
>         (fn foo.p)
>         (foo.z)))
> 
> hope that I've got the annotation correct, it's supposed to mean that
> the parameter z of foo is a reference type.  I would not expect fn to be
> polyinstantiated and is also what I mean by having only the polymorphic
> members boxed.  The other types would remain unboxed and available for
> use without polyinstantiation of the function.

The correct annotation for what you mean is:

(define foo:(forall ((refType 'a)) (fn (foo 'a) 'a))
    ... )

and I think this will achieve what you want.

> I think that the sort of algorithms you are thinking about though are
> the more generic containers that don't work very nicely in C without lots
> of type casting.

I am a little confused about this paragraph. Are you talking about the C 
code emitted by the compiler? Or, are you saying that this cannot 
otherwise be done from C ? Or, are you concerned about linking C code 
with instantiated procedures?

Swaroop.