Re: GNAT GPL 2009 - issue with floating points?

[Adam Beneschan <adam@irvine.com>]

On Oct 9, 3:15 pm, Damien Carbonne <damien.carbo...@free.fr> wrote:
> Adam Beneschan a écrit :
> >> -- pack04.ads:4:24: non-static expression used in number declaration
> >> -- pack04.ads:4:28: size attribute is only static for scalar type (RM
> >> 4.9(7,8))
>
> >> RM 3.5(1): "scalar types comprise enumeration types, integer types, and
> >> real types."
>
> >> RM 3.5.6 (1): "Real types provide approximations to the real numbers,
> >> with relative bounds on errors for floating point types, and with
> >> absolute bounds for fixed point types."
>
> > Did you read the RM reference that the GNAT error message pointed you
> > to???
>
> Yes I did !

The RM reference says (in paragraph 6) that the attribute reference
has to have a prefix that denotes a "static scalar subtype" (which is
defined later on in 4.9).  The GNAT message says just "scalar
subtype"; as Ludovic points out, that could have been worded better
and should probably have said "static scalar subtype".  However, one
should always trust the RM in preference to an error message, since
the RM is a standard.

Also, keep in mind that a "static" expression is basically one that
the compiler can determine at compile time when it sees the
expression, and in this case it can't, because it has no idea what
sort of float will be used to instantiate the package.

                                         -- Adam