Re: [Chicken-hackers] [PATCH] [CHICKEN 5] Change numerics representations

[John Cowan]

Peter Bex scripsit:

> That's not their main usefulness.  The main usefulness is that you can
> treat them like any other _pointer_ type, yet they can be kept apart
> if you want to by checking the tag.

Quite so.  They are pointers, but the tag allows you to factor them
into Scheme-detectable types without losing their pointer nature.
In essence, they let you subtype pointers.

> My main concern, after giving it some more thought, is that you can't
> easily make the FFI check the pointer type, unless you enforce that
> pointer tags are somehow either compile-time constants, or also stored
> in some global that's directly accessible to the FFI.  

As someone who has used them in the past, I would be quite content to
require that tags be symbols.

-- 
John Cowan          http://www.ccil.org/~cowan        address@hidden
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