On Jul 13, 2010, at 3:56 PM, Stéphane Ducasse wrote:
> Strange this is not what gilad mentioned.
> A pluggable type system: you can plug multiples one and the runtime is not
> influenced by type systems.
>
Yes.
Gradual Typing is *not* about multiple type systems. It's just *one* Type
System. Which has the
nice property of dealing nicely with code in the case of having no type
annotations.
One can implement Gradual Typing without any Pluggable Types. Then it's the
only type-system the
language has. Type-check would in this case not be optional. It would be always
done, but without
annotations leading to no static checking done. But it could actually influence
the language semantics
(e.g. one could imagine a language that compiles in dynamic checks following
the gradual type
checker in the case of no annotation. Instead of a runtime that has the checks
build in like smalltalk).
In turn, one could provide a Type-System based on Gradual Typing *on top* of a
Pluggable Types
infrastrustructure.This then would be a type-system that is optional, not
influencing language semantics.
So both are orthogonal. But of course related. (how to type-check dynamic
systems without making them static).
Marcus
--
Marcus Denker -- http://www.marcusdenker.de
INRIA Lille -- Nord Europe. Team RMoD.
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