Re: Top 10 Language Constructs (Ada)

[Florian Weimer <fw@deneb.enyo.de>]

"Dr. Joachim Schr�er" <joachim.schroeer@vs.dasa.de> writes:

> > for Plasma_Volts_Type'Small use Plasma_Volts_Type'Delta;
> 
> At least with GNAT 3.12p this statement does not compile. The error message
> is:
> 
> testfixpoint.adb:9:01: representation item appears too late
> testfixpoint.adb:9:01: warning: no more representation items for type
> "Plasma_Volts_Type" defined at line 7

The expression in the attribute definition clause is static
[3.5.10(2)], static expressions cause freezing [13.14(8)], as a
result, the corresponding type is frozen [13.14(10)]. [13.1(9)]
reads:

  9. A representation item that directly specifies an aspect of a
     subtype or type shall appear after the type is completely defined,
     see 3.11.1, and before the subtype or type is frozen, see 13.14. 
     [...]

I don't know what "before" means in this context exactly, but I think
the GNAT behavior is correct, even though the expression which causes
freezing doesn't appear before the representation item, strictly
speaking.