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Re^2: Example 2: incrementing "something"

by Mabooka-Mabooka (Sexton)
on Apr 17, 2005 at 04:35 UTC ( #448578=note: print w/ replies, xml ) Need Help??


in reply to Re: Common Beginner Mistakes
in thread Common Beginner Mistakes

Perl allows to use arithmetics on string

Here's the code:
#!/usr/local/bin/perl -w use strict; sub step_over_desert # () I won't repeat this mistake anymore!!! { print "Tsock...\n"; } sub cover_the_distance # () I won't repeat this mistake anymore!!! { my ($me, $desert_width, $max_spit_distance, $num_legs, $last_name, + $day_phone, $days_without_water) = @_; my $num_steps=0; while($desert_width) { my $todo = $desert_width * $num_legs; print "$desert_width miles remaining; $todo steps yet to do.\n" +; step_over_desert(); $desert_width--; $num_steps += $num_legs; } print "Steps made: $num_steps\n"; } #cover_the_distance("strong animal", 5, 15, 4, "Mabooka", "(123)-456-7 +890", -1); cover_the_distance("strong animal", "five thousand miles", 15, 4, "Mab +ooka", "(123)-456-7890", -1); 1;

Don't try it at home

Well, I recommend at the very least to redirect the output to a file:-).

Why people do this?

Again, the main reason: because it allows you. One may expect either a compile-time error or a run-time exception. But Perl allows you to shoot your own foot.
Actually, this is an obfuscated (starting to love the word) code from a real-life app. The real application would send a query over the wire to the server,
get a responce line --
-- that should look smth. like this:
200 OK 578
-- meaning " there're 578 lines yet to read from the socket,
parse this line and create a loop:
while($numlines) { get_next_one(...); $numlines--; ... }
Well guess what? Once in 10000 times the server would get tired and send a garbled status line -- smth. like:
200 OK whatever,man
and
(while "whatever,man"--) {....}
will start the almost infinite loop. (Try the code above).

Solution

Be aware.
use int($n).
Ask your new hires during the inteview: "What is the result of the following operation:
"Larry"--;
-?.


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