Ethiopian multiplication: Difference between revisions

=={{header|PHP}}==

<lang php><?php

function halve($x)

{

return floor($x/2);

}

function double($x)

{

return $x*2;

}

function iseven($x)

{

return ($x % 2) == 0;

}

function ethiopicmult($plier, $plicand, $tutor)

{

if ($tutor) { echo "ethiopic multiplication of $plier and $plicand\n"; }

$r = 0;

while($plier >= 1) {

if ( !iseven($plier) ) { $r += $plicand; }

if ($tutor) {

echo "$plier, $plicand " . (iseven($plier) ? "struck" : "kept") . "\n";

}

$plier = halve($plier);

$plicand = double($plicand);

}

return $r;

}

echo ethiopicmult(17, 34, true) . "\n";

?></lang>