here are the answers: Perl code:
sub reduce ($$) { my %hh= %{$_[0]}; # e.g. {'1,2'=>[1,2],'5,6'=>[5,6],...} my ($j1,$j2)=($_[1]->[0],$_[1]->[1]); # e.g. [3,4] delete $hh{"$j1,$j2"}; foreach my $k (keys %hh) { $k=~m/^(\d+),(\d+)$/; my ($k1,$k2)=($1,$2); if ($k1==$j1) { if ($j2 < $k2) { delete $hh{"$j2,$k2"}; } else { delete $hh{"$k2,$j2"}; }; }; if ($k2==$j1) { if ($k1 < $j2) { delete $hh{"$k1,$j2"}; } else { delete $hh{"$j2,$k1"}; }; }; } return \%hh; } ©Python code. © ©def reduce(pairings, pair): © ps=pairings.copy(); j=pair; © ps.pop("%d,%d"%(j[0],j[1]),0) © for k in pairings.itervalues(): © if (k[0]==j[0]): © if (j[1] < k[1]): © ps.pop("%d,%d"%(j[1],k[1]),0) © else: © ps.pop("%d,%d"%(k[1],j[1]),0) © if (k[1]==j[0]): © if (k[0] < j[1]): © ps.pop("%d,%d"%(k[0],j[1]),0) © else: © ps.pop("%d,%d"%(j[1],k[0]),0) © return ps © In imperative languages such as Perl and Python and Java, in general it is not safe to delete elements when looping thru a list-like entity. (it screws up the iteration) One must make a copy first, and work with the copy. Note also that in Python there's already a function called reduce. (it is equivalent to Mathematica's Fold.) In Python, looks like user can over-ride default functions. This post is archived at http://xahlee.org/perl-python/pairing_reduce.html Possible errata or addenda will appear there. Xah [EMAIL PROTECTED] http://xahlee.org/PageTwo_dir/more.html -- http://mail.python.org/mailman/listinfo/python-list