The semantics of "has" is complicated, is there a possibility that we make
it clear and precise?
The first problem, in my mind, is the lack of distinguishability of
categories and attributes, so that
> Integer has Rint
will return false without any warning, for "Rint" is not a known Category in
Axiom, and therefore is treated
as attribute automatically. Currently all Category names begin with
uppercase letters, while attributes begin
with lowercase letters (with some exceptions, e.g.
NullSquare,JacobiIdentity). Can we make this as the
rule( and rename that uppercase attributes)?
Related to first problem, the name of attributes are not checked. There is a
Category AttributeRegistry in
src/algebra, which seems to work as the registry of all attributes, but it's
not used.
Another undocumented usage of "has" is even check the equality of domains,
try:
)abbrev package TEST Test
Test(T:Type):with
if T has Integer then Ring
which is intrinsic and too ad-hoc. Why does this exist?
Type can be returned as a value from a function, but this value cannot be
used directly to "has", but I enabled
this feature by adding only one line of code:
--in i-spec2.boot
uphas t ==
t isnt [op,type,prop] => nil
-- handler for category and attribute queries
+ type := objVal interpret(type)
type :=
isLocalVar(type) =>
$genValue => ["evaluateType", ["unabbrev", type]]
-- At this point, type will have already been reduced to
-- its object representation.
["devaluate", type]
MKQ unabbrev type
catCode :=
-- FIXME: when we come to support category valued variable
-- this code needs to be adapted.
prop := unabbrev prop
evaluateType0 prop => ["evaluateType", MKQ prop]
MKQ prop
code:=["newHasTest",type, catCode]
if $genValue then code := wrap timedEVALFUN code
putValue(op,objNew(code,$Boolean))
putModeSet(op,[$Boolean])
So that:
(1) -> f==()+->Integer
Type:
Void
(2) -> f() has Ring
(2) true
Type:
Boolean
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