Re: Help with Exceptions!

[johnherro@aol.com (John Herro)]

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?