bye...
Roel Wuyts
roel.wuyts at iam.unibe.ch
Tue Mar 11 22:50:00 UTC 2003
On Tuesday, March 11, 2003, at 10:56 PM, Richard A. O'Keefe wrote:
> Roel Wuyts <roel.wuyts at iam.unibe.ch> wrote:
> Let me rephrase: I was talking about OO static typing systems.
> Type systems for OO systems I know of are now looking more into
> typing generics, but are not quite there yet (in my opinion).
> Do you have some pointers to a complete OO language that has no
> typecasts?
>
> Well, much depends on what you think a typecast is.
> Does Eiffel's "conditional assignment" count?
> In Eiffel,
> lhs ?= rhs
> has the effect that if the run-time type of rhs is compatible with the
> compile-time type of lhs, then the value of rhs is assigned to lhs,
> otherwise lhs becomes a Void reference. Note that this cannot be used
> to subvert the type system; Eiffel has no features for that. The value
> of lhs is _always_ appropriate for its declared type.
>
> but extended records are not enough; they don't provide
> you full objects I thought. Do they have late binding of self? I
> thought they only provided a form of data sharing.
>
> I have no idea what you mean by data sharing, and I did not write
> "extenDED records" but "extenSIBLE records". More precisely, a value
> of one record type conforms to another record type if each of the
> fields in the second type appears in the first and the corresponding
> field types match up right. Of course self is late bound, why wouldn't
> it be?
Because in object-based languages (as opposed to object-oriented) it is
not. See VisualBasic before they were really OO. You had inheritance as
far as data was concerned, but you could not override methods (no late
binding of self).
I don't know O'CAML (well, I know the name), that is why I asked... but
I'll read the manual.
> Do read the O'CAML manual. I don't really like O'CAML syntax
> much (it's several functional language design generations out of date),
> but it's a powerful system and regularly wins speed races for compiled
> code.
>
>
Roel Wuyts Software
Composition Group
roel.wuyts at iam.unibe.ch University of Bern,
Switzerland
http://www.iam.unibe.ch/~wuyts/
Board Member of the European Smalltalk User Group: www.esug.org
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