Need to detect undefined array elements

Question

Hi:
How does one detect unassigned elements of an array. Consider...
type myarrtyp is table of char(1) index by binary_integer;
myarr myarrtyp;
myarr(1) := 'X';
myarr(3) := 'X';
for x in 0..3 loop
dbms_output.put_line(x || ': ' || myarr(x));
end loop;
This fails when it hits myarr(2). Message is "no data found"
If I try to detect a NULL in the loop...
for x in 0..3 loop
if myarr(x) is null
then
dbms_output.put_line(x || ': NULL');
else
dbms_output.put_line(x || ': ' || myarr(x));
end if;
end loop;
... it still fails, same reason.
Q: How can one sense that myarr(2) has not been assigned?
I'm thinking that behind the scenes, Oracle is just creating a table with two columns, one with the char(1) and the other with a NUMBER. When I do something like myarr(3) := 'X', it loads one record in the array table (values (3,'X')). When I try to get myarr(2), I get a "no data found" in the same sense that I would get a "no records found" in a more familiar SQL query. If true, then how can one sense "no data found" when refering to a PL/SQL table array indexed by a binary_integer?
One work around is to init the array with something like '-', then selectively overwrite with 'X'. You will be able to sense the '-'. But, since I don't know how big the array will need to be, and I don't want to spend the cycles initializing a ridiculously large array, I'd prefere a more elegant solution.
Thanks in Advance
-dave

Answer 1

Just add an exception handler in the loop to trap for the no_data_found condition:
for x in 0..3 loop
  begin
    dbms_output.put_line(x || ': ' || myarr(x));
  exception
    when no_data_found then
      null;  -- do nothing, handle the exception silently
      -- dbms_output.put_line('element ' || x || ' not initialized');
  end;  
end loop;