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Re: [Gnu-arch-users] Features command for arch

From: Tom Lord
Subject: Re: [Gnu-arch-users] Features command for arch
Date: Thu, 2 Sep 2004 11:12:01 -0700 (PDT)

    > From: David Allouche <address@hidden>

    > The proposal I have in mind (after discussion with Robert Collins) is
    > slightly more elaborate.

    >       * Features are static and describe only the compile-time state of
    >         tla.
    >       * The "feature mapping" F maps "feature names" N (strings) to
    >         "feature versions" V (nonnegative integers).
    >       * F(N):V+1 implies F(N):V.

    > This feature mapping F:string->integer can be transformed into a mapping
    > F:string->boolean. In the unlikely event you have a problem with the
    > math, please ask.


David is slying suggesting that for every feature mapping F and every
integer n we can define a mapping F_n whee

        F_n(name) := (n <= F(name))

To say that is to make an assertion about the natural "topology" of
feature assertions.

David: why this particular topology and not one with richer structure?
(or poorer structure, as Jblack suggested?)   Is there a "natural"
topology that might be the trump-card of topologies for feature
assertions?  If there is no "natural" topology then this is a design
opportunity to accomidate conflicting constraints by making an
otherwise arbitrary decision in a context-specific way --- and so in
that case (of no "natural" topology): what is our design space?

(Likewise, re the math, we have a slightly foggy language barrier
between us, afaict.)


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