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From: Philippe Torres <ptorres@laas.fr>
Subject: Re: use of attribute Pos
Date: 2000/10/12
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Pat Rogers wrote:
> 
> "Philippe Torres" <ptorres@laas.fr> wrote in message
> news:39E4A08D.B454CB1C@laas.fr...
> > Hi, do you think the following behaviour is normal ?
> > -----
> > subtype Upper is character range 'A'..'Z' ;
> > begin
> > Put(Upper'Pos('A')) ;
> > -----
> > Output : 65
> >
> > I was expecting 0 since 'A' is the first element of Upper but i got
> > the ranking of 'A' in the Character type.
> >
> > What's the point of defining constrained subtype if we can't use the
> > attributes on it ? Or am i missing something ?
> 
> A subtype does not introduce a new type -- it names a constraint on an
> existing type.  Understand that and all else follows.
> 
> You can indeed use the attributes on the subtype, but you must
> recognize that only those attributes that represent *constraints* will
> be different than those of the actual type in question.  Thus
> Upper'first will yield 'A', Upper'last will yield 'Z', and so on.
> 
> Its all in the "names for constraints" concept...
> 
OK. Thank you all for your answers.
I understand the behaviour on a subtype of "constraint" attributes are
the sole to change compared to the base class.
But now, i wonder why Alejandro's solution
----
type Upper is new Character range 'A'..'Z' ;
begin
Put(Upper'Pos('A')) ;
---
still manages to output 65 and not 0.

Since a different type is introduced, how does Pos still refer to
Character ?
Should not 'new' have broken all "links" between the types Character and
Upper ?

Philippe