Perl: the Markov chain saw PerlMonks

Re^5: Recursion: the Towers of Hanoi problem

by abitkin (Monk)
 on Oct 25, 2004 at 14:38 UTC ( #402234=note: print w/replies, xml ) Need Help??

Strangely, using my \$l=\$_[3]-- and using a(@_[0,2,1,3]) etc. doesn't work at all. @_ is not localised (\$_3 ends up very negative and the solution becomes deeply recursive), which makes me wonder if the above solution works. I haven't compared the output to the original solution's output.

from perlsub:
The array @_ is a local array, but its elements are aliases for the actual scalar parameters.

Basically, if you think about it, @_ has to be localized. Otherwise if you called a function inside a function (something I hope most of us do) your @_ array would be wiped out, leaving you with the parameters you sent into the child function you just called. The particular behavior your seeing is probably becuase the @_ array contains aliases to scalars.

Second, using 0 based discs is okay, it's easy enough for the user to add 1 in their head (or to start thinking like a cs person.)

Third, and this is where it gets interesting, when removing all the whitespace I can I get (for your solution):

sub a{if(my\$l=pop){a(@_[0,2,1],\$l-1);print"Move disc \$l from \$_[0] to +\$_[2] ";a(@_[1,0,2],\$l-1);}}a 'A'..'C',pop;
Which just happens to be the same amount of space as (my solution):
sub a{my\$l=pop;a(@_[0,2,1],--\$l)."Move disc \$l from \$_[0] to \$_[2] ".a(@_[1,0,2],\$l)if\$l>0;}print a 'A'..'C',pop;
so it seems that both solutions are (atleast as far as this little experiment goes) equal. My goal is to squeeze everything that I have now down to 115 or 110 by Tuesday.

Oh and I have compared our outputs, and with the exception of the disc number (mine being one less than yours) they are exactly the same.

EDIT:
perlsub not perlvar

EDIT2:
pop instead of shift to remove chars

EDIT3 (10/26/04):
Best I've done, modifing jasper's code, is 111 chars.

sub a{if(my\$l=pop){a(@_[0,2,1],--\$l);print"Move disc \$l from \$_[0] to +\$_[2] ";a(@_[1,0,2],\$l);}}a 'A'..'C',pop;

==
Kwyjibo. A big, dumb, balding North American ape. With no chin.

Create A New User
Node Status?
node history
Node Type: note [id://402234]
help
Chatterbox?
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others avoiding work at the Monastery: (7)
As of 2018-04-25 10:57 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?
My travels bear the most uncanny semblance to ...

Results (89 votes). Check out past polls.

Notices?