[REBOL] Re: I hate computers!
From: rotenca:telvia:it at: 5-Jan-2003 2:41
Hi Andrew,
> determine whether a value of type DATATYPE! is a "physical" type or a
> "pseudo" type?
>
> >> Physical?: func [Datatype [datatype!]] [
> [ attempt [make Datatype 0 true]
> [ ]
> Basically trying to 'make the real value. Unfortunately, it doesn't work for
> 'function!, which requires two block! values and crashes Rebol when using a
> 0 value instead.
It does not work also for action!, datatype!, date!, error!, function!,
get-word!, library!, lit-word!, native!, object!, op!, port!, refinement!,
routine!, set-word!, struct!, symbol!, tuple!, unset!, word!
This function
t-d?: func [x][if error? set/any 'x try [make x] [x: disarm x return x/id <>
'cannot-use] true]
fails on:
action! datatype! native! op! unset!
This is a very empirical example which happens that fails only on unset! (but
is unset! a real datatype?):
t-d?: func [x /local y][
if parse/all second system/words [
to x skip to x y: skip to end
][return x = type? first y]
true
]
I think that we need some natives to works on datatype!, for example:
1) pseudo-datatype?
pseudo-datatype? any-string! ;== true
2) in-datatype?
in-datatype? any-string! string! ;== true
3) parent-datatype?
parent-datatype? string! ;== any-string!
parent-datatype? any-string! ;== series!
---
Ciao
Romano
