Bill Page wrote:
>
> Long ago on the axiom-devel list I expressed the opinion that the
> concept of "representation" implemented by Rep, rep and per are such a
> fundamental feature of SPAD/Aldor that they should be built-in to the
> compiler. In that vain it has always seemed strange that a common
> idiom in the language such as:
>
> Rep == SomeDomain
>
> (which looks like any other definition of a constant) is used to
> introduce this notion. Although some might argue that it is too late
> given the choice of Aldor and OpenAxiom, I still believe that Rep
> deserves a more unique place in the language. Having thought about
> this for a few years, here is one new suggestion that is still in
> keeping with the desire to keep the number of new keywords in SPAD to
> a minimum.
>
> Notice that the "add" keyword introduces a domain from which some code
> and it's associated **representation** while be inherited, so really
> there is no need to specify Rep in the following case:
>
> Foo(...): with
> ...
> == OldDomain add
> ... rep ... per ...
>
> The Rep in Foo must be the same as Rep in OldDomain.
>
> On the other hand, if there is no OldDomain then it is necessary to
> specify the domain that will represent this new domain. We could do it
> like this:
>
> Foo(...): with
> ...
> == Rep(SomeDomain) add
> ... rep ... per ...
>
> The general semantics of Rep(SomeDomain) would be exactly the same as
>
> Rep == SomeDomain
>
> in Aldor and OpenAxiom.
>
Well, currently assignment (or definition) of Rep has magical
properties. You propose to replace it by introducing magical
Rep constructor. I do not think this is good idea. First,
it is confusing -- AFAICS Gaby interpreted you proposal quite
different than myself, so at least one of us is confused.
Second, IIUC your proposal you replace small irregularity by a
big one. Namely, in various places assignment to variables is
used to introduce special behaviour -- so assignment or
definition of Rep is not a big deal. OTOH your proposed Rep
constructor is quite unlike any other use of constructors.
--
Waldek Hebisch
hebi...@math.uni.wroc.pl
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