As of revision 573, the interpreter now accepts calling a constructor
with a homogeneous variable length argument list, when the constructor
is defined to take a tuple. This new capability makes it possible
to define domains like Enumeration as ordinary OpenAxiom domains.
For example, given
)abbrev domain MYENUM MyEnum
MyEnum(enums: Tuple Symbol): Public == Private where
Public ==> SetCategory with
coerce: Symbol -> %
Private ==> add
Rep == NonNegativeInteger
coerce(s: Symbol): % ==
for i in 0..(length enums - 1) repeat
s = select(enums,i) => return per i
userError [s, "is not a valid enumerator"]
e1 = e2 ==
rep e1 = rep e2
coerce(e: %): OutputForm ==
select(enums, rep e)::OutputForm
I have
(1) -> WeekDay := MyEnum(Mon,Tue,Wed,Thu,Fri)
(1) MyEnum(Mon,Tue,Wed,Thu,Fri)
Type: Domain
(2) -> Mon :: WeekDay
(2) Mon
Type: MyEnum(Mon,Tue,Wed,Thu,Fri)
(3) -> Sat::WeekDay
>> Apparent user error:
Sat
is not a valid enumerator
Now, I don't see much reason not to define the builtin type Enumeration
as an ordinary domain. [1]
-- Gaby
[1] In fact I know of a reason: Equality of domains is not well
defined, for constructor instantiations involving vectors and the
like.
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