Re: [RFC] Alternate approach to keeping convenience variables

[Andrew STUBBS <andrew.stubbs@st.com>]

Jim Blandy wrote:
> On 1/24/06, Daniel Jacobowitz <drow@false.org> wrote:
>>> Right, but there's no way to test for that in the scripting language.
>>> Your 'init-if-undefined' command has to be a primitive, implemented in
>>> C.  My argument was that having the variables always be present is
>>> more convenient for user-defined commands.
>> Andrew's point is that such a primitive was recently committed :-)
> 
> If you want your user-defined command to print a helpful error mesage,
> you can't use that in an 'if'.  If we had some operator like
> $defined($foo), then that'd be different.

I'm not totally sure what you mean by this.

I put the following into the wavefront GDB and it works as I expected:

define defined
  set $temp = $arg0
  init-if-undefined $temp = 99999
  if $temp == 99999
   echo $arg0 not defined\n
  end
end


(gdb) defined $a
$a not defined
(gdb) defined $tpnum
(gdb)

It has its limitations, of course, but it does work. Your suggestion 
would still be better.