Re: Love's exception handling

Re: Love's exception handling

[Chris Sparks]

I was experimenting with Mr. Love's exception handling example.

This was my first working version.  I then proceeded to clean up this example
and came up with code following after this.

-------------------------------------------------------------------------------
> with Ada.Exceptions; use Ada.Exceptions;
> with Text_io;        use Text_io;
>
> procedure Exception_demo is
>
>   type A_String is access String;
>
>   Error_list: array (1..3) of A_String;
>
>   procedure Square is begin
>
>     raise Constraint_error;
>
>   exception
>     when Error_in_square_function: others =>
>
>       declare
>
>         Eo : Exception_Occurrence;
>         Ei : Exception_Id;
>
>       begin
>         Ada.Exceptions.Save_occurrence (Eo, Error_in_square_function);
>
>         Ei            := Exception_identity (Eo);
>         Error_List(1) := new String'(Exception_name (Ei) & " was hit Square");
>
>         Raise_exception (Ei, Error_List(1).all);
>
>       end;
>
>   end Square;
>
>   procedure Compute is begin
>
>     Square;
>
>   exception
>     when Error_in_compute: others =>
>
>       declare
>
>         Eo : Exception_Occurrence;
>         Ei : Exception_Id;
>
>       begin
>         Ada.Exceptions.Save_occurrence (Eo, Error_in_compute);
>
>         Ei            := Exception_identity (Eo);
>         Error_List(2) := new String'(Exception_name (Ei) & " was hit
 Compute");
>
>         Raise_exception (Ei, Error_List(2).all);
>
>       end;
>
>   end Compute;
>
> begin
>
>   Compute;
>
> exception
>   when Error_in_demo: others =>
>
>     declare
>
>       Eo : Exception_Occurrence;
>       Ei : Exception_Id;
>
>     begin
>       Ada.Exceptions.Save_occurrence (Eo, Error_in_demo);
>
>       Ei            := Exception_identity (Eo);
>       Error_List(3) := new String'(Exception_name (Ei) & " was hit
 Exception_Demo");
>
>     end;
>
>     for I in Error_list'range loop
> --    Text_io.Put_line ("Message    : " & Exception_message
 (Error_list(I).EO));
> --    Text_io.Put_line ("Name       : " & Exception_name
 (Error_list(I).EO));
> --    Text_io.Put_line ("Informaton : " & Exception_information
 (Error_list(I).EO));
>       Text_io.Put_line ("Info       : " & Error_list(I).all);
>     end loop;
>
> end Exception_demo;

-------------------------------------------------------------------------------

I thought the following might be useful to others.  That is why I am posting
this to cla.  It probably can be cleaned up to use internal data structures
instead of a constrained array (like linked lists).

What would be nice, in accordance with a previous post I sent out, to be able
to ascertain the program name without explicitly using a string literal. :-)

This a freebee, so enjoy.  BTW no one should try to copyright this okay :-0

Chris B. Sparks (aka Mr. Ada)
sparks@aisf.com

-------------------------------------------------------------------------------

> with Ada.Exceptions; use Ada.Exceptions;
>
> package Ex is
>
>   type A_String is access String;
>
>   Error_list: array (1..3) of A_String;
>
>   procedure Handler
>     (Target  : in Exception_Occurrence_Access;
>      Index   : in Integer;
>      P_Name  : in String;
>      Elevate : in Boolean);
>
> end Ex;
> --------------------------
> package body Ex is
>
>   procedure Handler
>     (Target  : in Exception_Occurrence_Access;
>      Index   : in Integer;
>      P_Name  : in String;
>      Elevate : in Boolean) is
>
>     Ei : Exception_Id;
>
>   begin
>     Ei                 := Exception_identity (Target.all);
>     Error_List (Index) := new String'(P_Name & ":" & Exception_name (Ei));
>
>     case Elevate is
>       when True  => Raise_exception (Ei, Error_List (Index).all);
>       when False => null;
>     end case;
>
>   end Handler;
>
> end Ex;
> --------------------------
> with Ada.Exceptions; use Ada.Exceptions;
> with Text_io;        use Text_io;
> with Ex;             use Ex;
>
> procedure Exception_demo is
>
>   procedure Square is begin
>
>     raise Constraint_error;
>
>   exception
>     when Error_in_square_function: others =>
>       Ex.Handler (Save_Occurrence (Error_in_Square_Function), 1, "Square",
 True);
>
>   end Square;
>
>   procedure Compute is begin
>
>     Square;
>
>   exception
>     when Error_in_compute: others =>
>       Ex.Handler (Save_Occurrence (Error_in_compute), 2, "Compute", True);
>
>   end Compute;
>
> begin
>
>   Compute;
>
> exception
>   when Error_in_demo: others =>
>     Ex.Handler (Save_Occurrence (Error_in_Demo), 3, "Exception_Demo", False);
>
>     for I in Error_list'range loop
>       Text_io.Put_line ("Info : " & Error_list(I).all);
>     end loop;
>
> end Exception_demo;

Re: Love's exception handling

[Robert B. Love]

In <INFO-ADA%96091315275250@LISTSERV.NODAK.EDU> Chris Sparks wrote:
> I was experimenting with Mr. Love's exception handling example.
> 
> This a freebee, so enjoy.  BTW no one should try to copyright this 
okay :-0

Uh, the original source for this is the current issue of the Journal
of Object Oriented Programming in the monthly Ada column written by
Richard Riehle.  I made only 2 minor changes so all 
credit/blame/copyright/
gratitude goes to him. 
 
This had proved most instructional to me, from learing about new
exception features, to playing with competing compilers.

----------------------------------------------------------------
Bob Love, rlove@neosoft.com (local)        MIME & NeXT Mail OK
rlove@raptor.rmnug.org  (permanent)        PGP key available
----------------------------------------------------------------

Re: Love's exception handling

[Richard Riehle]

On 16 Sep 1996, Robert B. Love wrote:

> Uh, the original source for this is the current issue of the Journal
> of Object Oriented Programming in the monthly Ada column written by
> Richard Riehle.  I made only 2 minor changes so all
> credit/blame/copyright/
> gratitude goes to him.

  Thank you Robert. My hide is relatively durable, so I accept any
  criticism directed toward my exception example. I am trying to
  include provocative examples in my JOOP column, so comments on
  alternatives to my examples are quite welcome. In fact, we can
  arrange to include some of them in the Letters section if the
  editor of JOOP agrees on their potential virtue.

> This had proved most instructional to me, from learing about new
> exception features, to playing with competing compilers.

  Glad to hear this. I am finding that many people are so enamoured
  of the OOP features of the new standard they overlook some of the
  more powerful extensions represented by such packages as
  Ada.Exceptions.  That was my reason for departing from strictly
  OOP theme in this article and focusing on this incredibily useful
  new feature of Ada 95.

  As to the copyright issue, I have no need to make any claims. The
  publisher may have some interest in this, but they would lose their
  subscribers pretty quickly if they started nitpicking about people
  actually using the code examples to learn and do real work.

  Richard Riehle

Re: Love's exception handling

[Richard Riehle]

Reposting article removed by rogue canceller.

On 16 Sep 1996, Robert B. Love wrote:

> Uh, the original source for this is the current issue of the Journal
> of Object Oriented Programming in the monthly Ada column written by
> Richard Riehle.  I made only 2 minor changes so all
> credit/blame/copyright/
> gratitude goes to him.

  Thank you Robert. My hide is relatively durable, so I accept any
  criticism directed toward my exception example. I am trying to
  include provocative examples in my JOOP column, so comments on
  alternatives to my examples are quite welcome. In fact, we can
  arrange to include some of them in the Letters section if the
  editor of JOOP agrees on their potential virtue.

> This had proved most instructional to me, from learing about new
> exception features, to playing with competing compilers.

  Glad to hear this. I am finding that many people are so enamoured
  of the OOP features of the new standard they overlook some of the
  more powerful extensions represented by such packages as
  Ada.Exceptions.  That was my reason for departing from strictly
  OOP theme in this article and focusing on this incredibily useful
  new feature of Ada 95.

  As to the copyright issue, I have no need to make any claims. The
  publisher may have some interest in this, but they would lose their
  subscribers pretty quickly if they started nitpicking about people
  actually using the code examples to learn and do real work.

  Richard Riehle