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Date: Mon, 25 Apr 2005 11:44:50 -0400
From: James Alan Farrell <jfarrell@grammatech.com>
Organization: GrammaTech, Inc.
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Newsgroups: comp.lang.ada
Subject: Syntax question:  new with a constrained subtype indication
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Date: 2005-04-25T11:44:50-04:00
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Hi all,
I'm working on software to analyze Ada programs using ASIS.  As such I 
need to make sure I handle all cases in the syntax (and I'm finding that 
in past assignments I've used only a small portion of the whole language!)

I'm currently working on a piece of code to analyze allocator 
expressions (ARM 4.8).  The entire relevant syntax is:

  4.8:
  allocator ::=
     new subtype_indication | new qualified_expression

  3.2.2:
  subtype_indication ::=  subtype_mark [constraint]

  3.2.2:
  subtype_mark ::= subtype_name

  3.2.2:
  constraint ::= scalar_constraint | composite_constraint

  3.2.2:
  scalar_constraint ::=
       range_constraint | digits_constraint | delta_constraint

  3.5
  range_constraint ::= range range

  3.5:
  range ::=  range_attribute_reference
    | simple_expression .. simple_expression

 From this, it appears I should be able to do something like:

package body Mod1 is

    procedure Proc1 is

       type Vector    is array (Integer range <>) of Float;
       type VectorPtr is access Vector;

       V : VectorPtr;

    begin
       V := new Vector range 1 .. 10;
    end Proc1;

end mod1;

Using gnat 3.15p, I get this error:

mod1.adb:15:23: incorrect constraint for this kind of type
gnatmake: "mod1.adb" compilation error

I suspect this is a type issue, but let me know if there is something 
incorrect in the syntax.

The thing is, I've read 4.8 of the *annotated* ARM and I don't see 
anything to say I cannot do this.  So what am I missing?  Is there 
something, other than that document, that spells out the allowed types 
of constraint?

Thank you,
James Alan Farrell