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From: Marc C <mc.provisional@gmail.com>
Newsgroups: comp.lang.ada
Subject: Labeled exit within generalized labeled loop not allowed?
Date: Fri, 13 Jul 2012 09:19:37 -0700 (PDT)
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Date: 2012-07-13T09:19:37-07:00
List-Id: <comp.lang.ada>

I find it hard to believe that this would be a GNAT GPL 2012 compiler bug, but I don't see anything in the LRM that indicates this wouldn't be legal.

Code containing a labeled generalized loop (the "for Elem of Some_Container" type), with a conditional exit referencing the loop label, fails to compile with an "Invalid loop name in exit statement" error.

What's the rationale for this? Or a consequence of what? Or is it a compiler bug?

Marc A. Criley

Here's an example:

with Text_IO; use Text_IO;

procedure Loop_Check is

   type Int_Array_Type is array (1..10) of Integer;
   
   IA : Int_Array_Type := (6 => 6, others => 3);
   
begin
   Loop_A: For I in IA'range loop
      Put_Line(Integer'Image(IA(I)));
      exit Loop_A When IA(I) = 6;
   end loop Loop_A;
   
   Loop_B: For I of IA loop
      Put_Line(Integer'Image(I));
      exit when I = 6;
   end loop Loop_B;
   
   Loop_C: For I of IA loop
      Put_Line(Integer'Image(I));
      exit Loop_C when I = 6; -- Compiler error on this line
   end loop Loop_C;
end Loop_Check;