Euclid's algorithm for finding the Greatest Common Divisor and Least Common Multiple

Euclid's algorithm for finding the Greatest Common Divisor of two numbers.
And its partner the Least Common Multiple
Usage:

echo(gcd(90,15));
echo(lcm(5,4));

function gcd(a,b)=
 a<=0||b<=0?min(sign(a),sign(b)):
   a % b==0?b:

   gcd(b,a % b);

function lcm(a,b)= a * (b / gcd(a, b));