Re: tilde operator

["Loren J. Rittle" <rittle@supra.rsch.comm.mot.com>]

Harald and the list,

You all have reminded me that many eyes make it easier to find bugs in
one's thinking.  I actually feel kind of dumb since I knew the details
(one-scan rule, eval to re-scan, quoting pattern when assigning to a
variable - this flaw was only in the posted example code), I just
didn't put them together right.

As I replied to Byron, based upon his advice, this was the "solution"
to make the middle example print 0:

S rittle@supra; h='x*'; echo <={eval '~' x1 $h}
0

Although I didn't mention it, before I mailed the list, I had tried:

S rittle@supra; h='x*'; echo <={eval ~ x1 $h}
/usr/users/rittle: Permission denied

At the time, it just didn't seem right to have to quote '~' (I wont
even claim to have thought about even trying that), but now it makes
perfect sense.  Harald, I think you said it best (paraphrased),
~``eval: Here be dragons''.

Thanks to:

Harald Hanche-Olsen <hanche@math.ntnu.no>
Bill Trost <trost@cloud.rain.com>
Byron Rakitzis <byron@rakitzis.com>
<rsc@plan9.bell-labs.com>

Regards,
Loren