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Subject: Re: choice_expression
From: Maxim Reznik <reznikmm@gmail.com>
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Date: 2012-10-08T08:44:11-07:00
List-Id: <comp.lang.ada>

=D0=BF=D0=BE=D0=BD=D0=B5=D0=B4=D0=B5=D0=BB=D1=8C=D0=BD=D0=B8=D0=BA, 8 =D0=
=BE=D0=BA=D1=82=D1=8F=D0=B1=D1=80=D1=8F 2012=C2=A0=D0=B3., 17:49:05 UTC+3 =
=D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Ad=
am Beneschan =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:
> On Monday, October 8, 2012 6:34:27 AM UTC-7, Maxim Reznik wrote:
>=20
> > BTW GNAT understands it as "(False in False) and False"
>=20
>=20
>=20
> If this isn't a typo, then GNAT is wrong; "and" has a higher precedence t=
han "in", so that A in B and C should be intepreted as A in (B and C).
>=20

I belive priority of membership test is the same as for relational_operator=
, because both of them are in the same syntax rule, so interpretation shoul=
d be the same as for "A < B and C" =3D> "(A<B) and C". This equals to GNAT'=
s one.

But force user to guess operator precedence is not good. Ada 83 avoided it =
long ago and I don't understand why Ada 2012 does it in other way even by c=
omplicated syntax.


>=20
> I personally can't imagine using a construct "X in ..." where X is a bool=
ean expression.  It seems highly useless,=20
[skipped]

Neither I can't.

It looks strange why language designers added couple of dedicated ARM rules=
 to allow useless constructs with unclear, ambiguous and error-prone syntax=
 :(