Recipes for PDSC #2: Hashes of Lists

Declaration of a HASH OF LISTS:

%HoL = (        "flintstones"        => [ "fred", "barney" ],       "jetsons"            => [ "george", "jane", "elroy" ],       "simpsons"           => [ "homer", "marge", "bart" ],     );

Generation of a HASH OF LISTS:

# reading from file# flintstones: fred barney wilma dinowhile ( <> ) {    next unless s/^(.*?):\s*//;    $HoL{$1} = [ split ];}# reading from file; more temps# flintstones: fred barney wilma dinowhile ( $line = <> ) {    ($who, $rest) = split /:\s*/, $line, 2;    @fields = split ' ', $rest;    $HoL{$who} = [ @fields ];}# calling a function that returns a listfor $group ( "simpsons", "jetsons", "flintstones" ) {    $HoL{$group} = [ get_family($group) ];}# likewise, but using tempsfor $group ( "simpsons", "jetsons", "flintstones" ) {    @members = get_family($group);    $HoL{$group} = [ @members ];}# append new members to an existing familypush @{ $HoL{"flintstones"} }, "wilma", "betty";

Access and Printing of a HASH OF LISTS:

# one element$HoL{flintstones}[0] = "Fred";# another element$HoL{simpsons}[1] =~ s/(\w)/\u$1/;# print the whole thing foreach $family ( keys %HoL ) {    print "$family: @{ $HoL{$family} }\n"}# print the whole thing with indicesforeach $family ( keys %HoL ) {    print "family: ";    foreach $i ( 0 .. $#{ $HoL{$family} } ) {	print " $i = $HoL{$family}[$i]";    }    print "\n";}# print the whole thing sorted by number of membersforeach $family ( sort { @{$HoL{$b}} <=> @{$HoL{$b}} } keys %HoL ) {    print "$family: @{ $HoL{$family} }\n"}# print the whole thing sorted by number of members and nameforeach $family ( sort { @{$HoL{$b}} <=> @{$HoL{$a}} } keys %HoL ) {    print "$family: ", join(", ", sort @{ $HoL{$family}), "\n";}