Re: class wide object in generic package

[Craig Carey <research@ada95.ijs.com>]

On Mon, 10 Jun 2002 09:38:15 +0200, Thomas Maier-Komor
<maierkom@rcs.ei.tum.de> wrote:

...
>I am getting this error message when compiling the
>code at the end of the message:
>
>generic_pac.adb:7:26: class-wide argument not allowed here
>generic_pac.adb:7:26: "eval" is not a primitive operation of "Object"
>
...

>second: why isn't a class-wide argument not allowed
>in this place?
>

That error message is one that GNAT 3.14p for NT produces, and it
identifies the 2nd "a" in the text "eval (g.p.all)", in the
generic_pac.adb file.

Putting in a type conversion to solve the Object vs Object'Class
mismatch, causes that error to not appear. Here is GNAT listing
output:

| gnatmake generic_pac.adb -gnatl -gnatwa -gnata -gnato -gnatq -gnatf
|  -v -gnatU -gnatn -g -O0 -gnaty3abcefhikrlM79pts -gnatwa -bargs -E
|  -p -we -static -largs -v -v -L.


|File: generic_pac.ads
|     1. generic
|     2.    type Object is abstract tagged private;
|     3.    type Pointer is access all Object'class;
|     4.    with procedure eval (o : in out Object);
|     5.
|     6. package generic_pac is
|     7.    type gen is record
|     8.       p : Pointer;
|     9.    end record;
|    10.
|    11.    procedure use_it (g : in out gen);
|    12.
|    13. end generic_pac;
|
|File: generic_pac.adb
|     1. with Ada.Text_IO; use Ada.Text_IO;
|     2.
|     3. package body generic_pac is
|     4.    procedure use_it (g : in out gen) is
|     5.    begin
|     6.       Put_Line ("generic_pac.use_it");
|     7.       eval (Object (g.p.all));
|     8.    end use_it;
|     9. end generic_pac;
|

Craig Carey / Ada mailing lists: http://www.ijs.co.nz/ada_95.htm