Monday, 25 February 2008

scales balancing puzzle check

see perl script


=head1 NAME - check you can make each weight from 1 to 40 balance


This doesn't solve the puzzle but does prove that the solution works.

The puzzle is you have a balance (bilancia in Italian).
And you can choose some unit weights to help weigh things.
If you get any unit weight from 1 to 40 you need to be able to determine the weight.
(You have to make the scales balance, you're not allowed to measure
it as lighter than w+1 and heavier than w-1 hence is w.)
What is the minimum number of weights you can do this in ?

If the puzzle is told properly then you probably have to bring the
balance and weights up a big mountain with dragons on top so you wish to use the absolute minimum
number of weights (or possibly minimum weight of weights - is it the same answer I wonder?)


my @weights = ( 1, 3, 9, 27 );

for(my $w=-1; $w<=41; $w++) {

# brute force, try balance all permutations, weights on both sizes

# try position of not there, left, right for each weight
my @weight_pos = ( 0, 0, 0, 0 );
my $wi = 0;

# print terrible message if not found otherwise might miss one
my $terribleness = "BAH! :( not good, no match for $w\n";
my $found = 0;

for($weight_pos[0]=0; $weight_pos[0]<3 && $found==0; $weight_pos[0]++) {
for($weight_pos[1]=0; $weight_pos[1]<3 && $found==0; $weight_pos[1]++) {
for($weight_pos[2]=0; $weight_pos[2]<3 && $found==0; $weight_pos[2]++) {
for($weight_pos[3]=0; $weight_pos[3]<3 && $found==0; $weight_pos[3]++) {

# start with $w always on left
my $left_tot = $w;
my $right_tot = 0;
my @leftside = ( $w );
my @rightside = ();

# print '$#weights is ' . $#weights . " (number of elements in weights array)\n";

# put weights on balance
for($wi=0;$wi<=$#weights;$wi++) {

#print "dbg w=$w wi=$wi pos=$weight_pos[$wi]\n";

if ($weight_pos[$wi] == 1) {
#printf "L";
push @leftside, $weights[$wi];
$left_tot += $weights[$wi];
} elsif ($weight_pos[$wi] == 2) {
#printf "R";
push @rightside, $weights[$wi];
$right_tot += $weights[$wi];
#$ls += "(".$weights[$wi].) ";
#$rs += "(".$weights[$wi].) ";

#print "dbg w: $w, balance $left_tot = $right_tot, left: @leftside - right: @rightside\n";

if ($left_tot == $right_tot) {
print "w: $w, balance $left_tot = $right_tot, left: @leftside - right: @rightside\n";
$terribleness = "";
$found = 1;


print $terribleness;

perldoc is a good reference, (command-line interface to perl docs)
not on all machines but is on slaine
same stuff as is on web in lots of places of course:

e.g. perldoc perl, perldoc perldoc (for table of contents)
perldoc perlsyn
perldoc perlre

-f or -q to get function documentation or search faq:

perldoc -f printf
perldoc -q while

After you know all that perldoc then you can start thinking about using perl modules! :D

To read perl documentation _inside_ perl scripts or modules just do e.g.:


Saturday, 23 February 2008

"Oh ye broke me cups and saucers"

I've set me playing the recorder of the tune of "cups and saucers" as ringtone for Mum :)
I started with "Moll Dubh" for Fionnuala.
Quite a striking mobile ringtone! :-o

Mum remembers her dad singing this chorus, and only the chorus:

Oh ye broke me cups and saucers
Oh ye did ye rogue, oh ye did ye rogue
Oh ye broke me cups and saucers
Oh ye did ye rogue, oh ye did ye rogue

Much grepping of internet reveals those lyrics are nowhere!
Maybe on an album by Bobby Gardiner - The Clare Shout - song The Kerry Cow, Cups and Saucers
Someone says on comments "It's called Cups and Saucers on Bobby Gardiner's album "The Clare Shout". He lilts the tune and runs it into the song "Cups and Saucers" (of the same tune).
Maybe that is song eilzab is talking about." seems to be quite a good source for information on irish tunes.
lyrics, sheet music and ABC music
Also known as "Bhiosa La I BPort Lairge", Cups And Saucers, False Knight On The Road, The False Knight On The Road, I'll Cloot My Johnny's Breeches, Let's Pet The Pope, Little May Cullinane, O, I Courted A Farmer's Daughter, Port Lairgè, Portlairge, Portláirge, Dashing White Sergent, White Cockade

And in can find various renditions of "The False Knight on the
Road" ... and one or two of them have the same tune.