From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,FREEMAIL_FROM,
	INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,deeb88b0e7eede4f
X-Google-Attributes: gid103376,public
From: johnherro@aol.com (John Herro)
Subject: Re: Help with Exceptions!
Date: 1996/05/07
Message-ID: <4mnj0f$kka@newsbf02.news.aol.com>#1/1
X-Deja-AN: 153493544
sender: root@newsbf02.news.aol.com
references: <4mmimq$s4r@hatathli.csulb.edu>
organization: America Online, Inc. (1-800-827-6364)
newsgroups: comp.lang.ada
Date: 1996-05-07T00:00:00+00:00
List-Id: <comp.lang.ada>


rgelb@csulb.edu (Robert Gelb) asks:
> ...when I catch an error with [an exception
> handler], how can I go back to statement
> where the error occured (or the statement
> next to it)?
     In Ada an exception handler is executed *instead of* the rest of the
procedure, function, block, etc. that raised the exception.  There's no
counterpart of Basic's RESUME or RESUME NEXT, and even a goto from an
exception handler back to the unit that raised the exception is forbidden!
 Therefore, place your exception handler in a small block, so that only a
small amount of code is skipped when the exception is raised, and place
the entire block in a loop that runs until the code executes correctly. 
For example, this program fragment will keep getting input until the user
types a valid integer; then it will go on:

Valid     : Boolean := False;
Input     : String(1 .. 80);
Input_Len : Integer;
Answer    : Integer;
...
while not Valid loop
   Put("Type an integer: ");
   Get_Line(Input, Input_Len);
   begin
      Answer := Integer'Value(Input(1 .. Input_Len));
      Valid  := True;
   exception
      when others => Put_Line("Invalid.  Please try again.");
   end;
end loop;

     Things are a bit more complicated for exceptions raised in a
*declarative* region, but most exceptions are raised in an executable
region.  There's a more detailed explanation of exceptions and exception
handlers in the Ada Tutor program, available for download at the Web and
ftp sites below my signature.
     I hope this helps.
- John Herro
Software Innovations Technology
http://members.aol.com/AdaTutor
ftp://members.aol.com/AdaTutor
     If a vegetarian is a person who eats vegetables, what does a
humanitarian eat?