Definition with Guards

Functions can be defined with guards:

valAbs :: Int -> Int
-- returns the absolute value of an integer

valAbs n
  | n >= 0 = n
  | otherwise = -n

  • Guard evaluation is top-down and returns the result of the first true branch.

  • Pattern definitions can also have guards.

  • The otherwise is the same as True, but more readable

Equality goes after every guard!