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Re: how typish are roles
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From:
Trey Harris
Date:
October 28, 2006 04:52
Subject:
Re: how typish are roles
Message ID:
20061028035552.V46238@bowser.eecs.harvard.edu
In a message dated Sat, 28 Oct 2006, chromatic writes:
> When you specify a type to constrain some operation, you specify that
> the target entity must perform that role.
That statement is very concise and direct. If the fuzziness I observed
about the identity of the basic building block of type was unintentional,
this statement should be added to S06.
>> I think the question (which you didn't directly raise, but I've heard
>> from others) of whether "role" or "class" will have primacy is kind of
>> as pointless as asking whether "subroutines" or "code blocks" have
>> primacy: you can't use the former without the latter; the former is a
>> useful abstraction for the latter, especially when code gets larger or
>> is meant for sharing; and while each have places where they're more
>> appropriate, either can be used in place of the other given a bit of
>> syntactic twiddling.
>
> Well... maybe. I believe strongly that you can build a really good
> system with roles as the fundamental abstraction and where classes are a
> specialization, but doing the other way around is much more difficult
> and less cohesive.
But I wasn't suggesting that, any more than I was suggesting that code
blocks based on anonymous subroutines would be as cohesive as subroutines
based on code blocks. I was just saying that both roles and classes could
be equally first-class participants in the type system by my reading of
S06 and S12: I don't see any necessity, short a statement like yours I
quoted above, for classes to be coerced into a role before they can act as
a type.
Trey
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