[CST-2] Types (NOT Opt Comp.) 1997/7/10

[Matej Pfajfar]

Well the language he gives doesn't seem to have type schemes.
So the rules & axioms of the type system don't exhibit the principal
type property.

Is that plausible?

On Fri, 24 May 2002, Alvin wrote:

> Hmm, maybe it just means whether generalisation is possible.  Eg the tuple
> rule:
>
> G |- M1 : t1    G |- M2 : t2
> -----------------------------
>     G |- (M1,M2) : t1 x t2
>
> Is a generalised form of
>
> G |- M1 : r     G |- M2 : r
> ---------------------------
>     G |- (M1,M2) : r x r
>
> Similarly for integers, functions etc
>
> Total guess, but it makes sense.
>
> Alvin
>
> > Sorry I just realised the mistake. The question (repeated below) is
> > clearly about Types, not Opt. Comp.
> >
> > Mat
> >
> >> The question asks to explain the notion of a principal type. Presumably
> >> the answer to this is that the principle type is just the principal type
> >> scheme.
> >> Then it also asks whether the set of type inference rules (for an ML-like
> >> language), which you had to give in the previous part of the question, has
> >> this propery.
> >> I am a bit confused as to how type inference rules exhibit a principal
> >> type property? Anyone?
> >> thanks,
> >>
> >> Mat
> >>
> >> Matej Pfajfar
> >> St John's College, University of Cambridge, UK
> >>
> >> GPG Public Key @ http://matejpfajfar.co.uk/keys
> >> Most people are good people, the rest of us are going to
> >> run the world. -- badbytes
> >>
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> >
> > Matej Pfajfar
> > St John's College, University of Cambridge, UK
> >
> > GPG Public Key @ http://matejpfajfar.co.uk/keys
> > Most people are good people, the rest of us are going to
> > run the world. -- badbytes
> >
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Matej Pfajfar
St John's College, University of Cambridge, UK

GPG Public Key @ http://matejpfajfar.co.uk/keys
Most people are good people, the rest of us are going to
run the world. -- badbytes

WARNING: THIS E-MAIL ACCOUNT WILL BE DELETED ON
         30/09/2002. PLEASE USE mp@cantab.net.