Beefy Boxes and Bandwidth Generously Provided by pair Networks
Do you know where your variables are?

Re: Neat Debugger tricks

by salva (Abbot)
on Nov 17, 2005 at 10:17 UTC ( #509353=note: print w/replies, xml ) Need Help??

in reply to Neat Debugger tricks

the new assertion subs, available on blead perl and on 5.10 in the future, act as conditional breakpoints under the debugger.

For example, this script uses an assertion to test that the argument passed to my_sqrt is a positive number:

#!/usr/local/bin/perl5.9.3 use assertions '1'; # assrt. are always active use strict; use warnings; sub assert (&@) :assertion { my $sub = shift; &{$sub}() or die "assertion failed: @_" } sub my_sqrt { my $n = shift; assert { $n >=0 } "argument has to be a positive number"; return sqrt($n); } for my $n (0.3, 0, -4, 7, 9) { printf "sqrt(%f) = %f\n", $n, my_sqrt($n); }
then running it under the debugger:
toledo:~# perl5.9.3 -d /tmp/ main::(/tmp/ for my $n (0.3, 0, -4, 7, 9) { DB<1> c sqrt(0.300000) = 0.547723 sqrt(0.000000) = 0.000000 assertion failed: argument has to be a positive number at /tmp/ l +ine 10. main::my_sqrt(/tmp/ return sqrt($n); DB<1> l 16==> return sqrt($n); 17 } 18 19: for my $n (0.3, 0, -4, 7, 9) { 20: printf "sqrt(%f) = %f\n", $n, my_sqrt($n); 21 } 22 DB<1> p $n -4

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://509353]
[LanX]: Let's Make PerlMonks Great Again!
[holli]: but you know what? i don't think i'd fancy that. I like PM as it is.
[holli]: Alone the chatterbox and everybody writes his own cb client tradition
[LanX]: there was a guy who tried to steal the concept and build an own monastery ...
[LanX]: yeah PM is very emacsy ;-)
[LanX]: I think tobyink was on a good track with his redesign, pitty the pmdevs/gods didn't try to continue the approach of a modern responsive design
[holli]: *sigh* why has there to be drama in such a thread?
[LanX]: ?
[holli]: Re^2: Let's Make PerlMonks Great Again! -- suggestions and dreams - STFU and write code already (start already)

How do I use this? | Other CB clients
Other Users?
Others studying the Monastery: (9)
As of 2017-11-20 19:37 GMT
Find Nodes?
    Voting Booth?
    In order to be able to say "I know Perl", you must have:

    Results (292 votes). Check out past polls.