CONTRAINT ERROR (was Re: parsing a string)

[pumilia@est.it]

In article <uu2k3kszb.fsf@gsfc.nasa.gov>,
  Stephen Leake <Stephen.Leake@gsfc.nasa.gov> wrote:

> Index is a function, which must be assigned to a value, so this can't
> be the real source. Please include your _complete_ test program, so we
> can compile it ourselves, to help get a good answer.
>
> The default for Map should be fine. You can find out what else you
> might pass for Map in the package Ada.Strings.Maps.
>
> -- Stephe
>

Ok, i simplified my program, adjusted something thanks to David Hoos's
and
your useful comments and found a new error: CONSTRAINT_ERROR.

Here is my test procedure, aimed to converting an unbounded string
to string and then to parse the string:

-- str2_test --------------------------------------
with   ada.strings.unbounded;
use    ada.strings.unbounded;
with    ustrings;
use      ustrings;
with   text_io;
with   Ada.Integer_Text_IO;
use    text_io;
with ada.strings.fixed; use ada.strings.fixed;

with Ada.Integer_Text_IO;
use Ada.Integer_Text_IO;

procedure str2_test is

 output_file_string : unbounded_string ;
 output_file : string (1..25) ;
 pos1 : natural;

Begin

    get_line(output_file_string);

   put(" output:  "); put(output_file_string); put("<--"); new_line;
   output_file :=  to_string(output_file_string);
   put(" Output:  "); put(output_file); put("<--"); new_line;
   put(" index:  "); pos1 := Index(output_file,"xxx");
   put(pos1);
   new_line;

end str2_test;
-- str2_test --------------------------------------


While executing i get the error:

>   raised constraint_error : str2_test.adb:24

This is line 24:

  output_file :=  to_string(output_file_string);


Any help wil be appreciiated
thank you
Pol

- ustrings.ads ---------------------------------
-- Ideally this would be a child package of "Ada.Strings.Unbounded".

-- package Ustrings is
--   procedure Get_Line(Item : out Unbounded_String);
--   procedure Put(Item : in Unbounded_String);
--   procedure Put_Line(Item : in Unbounded_String);
-- end Ustrings;
--
-- Copyright (C) 1996 Ada Resource Association (ARA), Columbus, Ohio.
-- Author: David A. Wheeler
--

with Text_IO, Ada.Strings.Unbounded;
use  Text_IO, Ada.Strings.Unbounded;

package Ustrings is

  -- This package provides a simpler way to work with type
  -- Unbounded_String, since this type will be used very often.
  -- Most users will want to ALSO with "Ada.Strings.Unbounded".
  -- Ideally this would be a child package of "Ada.Strings.Unbounded".
  --

  -- This package provides the following simplifications:
  --  + Shortens the type name from "Unbounded_String" to "Ustring".
  --  + Creates shorter function names for To_Unbounded_String, i.e.
  --    To_Ustring(U) and U(S).  "U" is not a very readable name, but
  --    it's such a common operation that a short name seems appropriate
  --    (this function is needed every time a String constant is used).
  --    It also creates S(U) as the reverse of U(S).
  --  + Adds other subprograms, currently just "Swap".
  --  + Other packages can use this package to provide other
simplifications.

  subtype Ustring is Unbounded_String;

  function To_Ustring(Source : String)  return Unbounded_String
                                         renames To_Unbounded_String;
  function U(Source : String)           return Unbounded_String
                                         renames To_Unbounded_String;
  function S(Source : Unbounded_String) return String
                                         renames To_String;

  -- "Swap" is important for reuse in some other packages, so we'll
define it.

  procedure Swap(Left, Right : in out Unbounded_String);


  function Empty(S : Unbounded_String) return Boolean;
   -- returns True if Length(S)=0.
  pragma Inline(Empty);


  -- I/O Routines.
  procedure Get_Line(File : in File_Type; Item : out Unbounded_String);
  procedure Get_Line(Item : out Unbounded_String);

  procedure Put(File : in File_Type; Item : in Unbounded_String);
  procedure Put(Item : in Unbounded_String);

  procedure Put_Line(File : in File_Type; Item : in Unbounded_String);
  procedure Put_Line(Item : in Unbounded_String);

end Ustrings;

- ustrings.ads ---------------------------------



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