disco-0.1.0.0: docs/tutorial/example/function-desugar.disco

gcd : N * N -> N
gcd(a,0) = a
gcd(a,b) = gcd(b, a mod b)

gcd2 : N * N -> N
gcd2 = λp. {? a                when p is (a,0),
              gcd2(b, a mod b) when p is (a,b)
           ?}