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From: AdaMagica <christoph.grein@eurocopter.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Containers Hash function for a set of small integers
Date: Mon, 26 Apr 2010 21:50:19 -0700 (PDT)
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> > =A0 =A0 =A0 =A0 =A0Result :=3D Result xor M (Integer'Pos (X) mod 2**31)=
;
> > =A0 =A0 =A0 =A0 =A0-- =A0No warning (and executes as I had expected)
> > =A0 =A0 =A0 =A0 =A0Put_Line ("result:" & M'Image (Result));
> > =A0 =A0 =A0 exception
> > =A0 =A0 =A0 =A0 =A0when others =3D> Put_Line ("exception c");
> > =A0 =A0 =A0 end;
> about the zero divisor. The Aonix ObjectAda 7.2 compiler ...
> gives an error at the third block (95LRM4.9(35)).

I'm no language lawyer, but I'll give it a try.

RM95 4.9(35): If the expression is not part of a larger static
expression, then its value shall be within the base range of its
expected type. Otherwise, the value may be arbitrarily large or small.

RM TC1 AM1 4.9(35/2) {AI95-00269-01} If the expression is not part of
a larger static expression *and the expression is expected to be of a
single specific type*, then its value shall be within the base range
of its expected type. Otherwise, the value may be arbitrarily large or
small.

Since Aonix quotes 95RM4.9(35), it must be a pure Ada95 compiler.
2**31 is not part or a larger static expression. The further condition
of being of a single specific type (which is not the case here, the
expected type is any integer type) was added later.

So Aonix is correct, and so is GNAT, if the latter is new enough to
obey AM1.