Well, if I'm allowed to generate a list of strings rather than a list
of lists, then I'll kick off the golfing with a strict compliant one
in 70 characters (inside of P):
#!/usr/bin/perl -w
use strict;
sub P {
my($i)=@_;push@_,grep!/[^1-$i]/,map"$i$_",P($_[0]-$i)and$i--while$i;@_
}
for(P(5)){
print "$_\n";
}
__END__
# output is
5
41
32
311
221
2111
11111
If you do insist on a list of lists, we can tack on the following
16 character wrapper sub to call instead of P:
sub W{map{[split//]}&P}
Update: In response to my major oversight that tilly's
followup points out, all I can say is:
"Rats! Last time I go golfing in the middle of the night!"
:-)
Update2:Ok, in the light of day, here's a recursive one in 82
chars (ignoring unnecessary whitespace) that returns a list of lists:
sub P{
my$i=my$n=pop;
push@_,grep{!grep{$_>$i}@$_}map{[$i,@$_]}P($n-$i)while$i-->1;
[$n],@_
}