I'm not sure if they teach you CS types this
stuff in school but I read it long ago and
recently come across it again, and I decided
to implement the algorythm in perl for s&g.
It's called ethiopian multiplication.
The premise is that peasants are not capable of
performing multiplication proper but commerce
has required them to implement a substitute.
#Division eq fractions eq multiplication...
sub mul{
#If peasants can't multiply they certainly can't grok fractions
use integer;
my ($i, $j) = @_;
my @results = ([$i, $j]);
#Halve until we can halve no more
while($i > 1){
my @z = ($i=halve($i), $j=double($j));
push @results, [@z];
}
my $total;
foreach( @results ){
#Even halves are evil
$total += $_->[1] if $_->[0] % 2;
}
return $total;
sub double{
#Cloning err doubling is easy;
$_[0]+=$_[0];
}
sub halve{
#Halving is a bit more tedious;
my $count=0;
while($_[0]>1){$_[0]-=2; $count++};
return $count;
}
}
And to think, it's almost 1/500_000th the speed
of CORE multiplication. There are of course,
overflow issues.
--
perl -pe "s/\b;([st])/'\1/mg"