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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Modes (was unbounded_string)
Date: 11 Oct 2003 08:16:39 +0100
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Date: 2003-10-11T08:16:39+01:00
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Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> writes:

> declare  -- I need the value of QUERY_STRING here
>    Temp : String renames Getenv ("QUERY_STRING").all;
>       -- Temp is an alias to the env-string. You cannot modify it.
>       -- Yet it is not a pointer. An analogue would be C++ reference
> begin
>    ... -- Doing with Temp everything I can to do to
>        -- a constant String
> end; -- I don't need it anymore

Actually you *can* modify it:

   with Ada.Text_IO; use Ada.Text_IO;
   with GNAT.OS_Lib; use GNAT.OS_Lib;

   procedure Env is
      Temp : String renames Getenv ("COLDFRAME").all;
   begin
      Temp (1) := 'x';
      Put_Line (Temp);
   end Env;

then

   smaug.pushface.org[5]$ COLDFRAME=foo ./env
   xoo

(GNAT 3.16a1)

Should GNAT.OS_Lib.Getenv have been defined as returning a constant
string access?

   type Constant_String_Access is access constant String;