fact.disco

-- Here are two equivalent definitions of factorial using the two
-- different styles: one with a case expression, and one with two
-- pattern-matching clauses.

fact : N -> N
fact n =
  {? 1            when n is 0,
     n * fact m   when n is m+1
  ?}

fact2 : N -> N
fact2 0 = 1
fact2 (m+1) = (m + 1) * fact2 m