  | 4 minutes, 22 seconds | The Order of Evaluation - slide 18 : 26 |
Conditionals and sequential boolean operators
There are functional language constructs - special forms - for which applicative order reduction would not make sense
- (if b x y)
- Depending on the value of b, either x or y are evaluated
- It would often be harmful to evaluate both x and y before the selection
- (define (fak n) (if (= n 0) 1 (* n (fak (- n 1)))))
- (and x y z)
- and evaluates its parameter from left to right
- In case x is false, there is no need to evaluate y and z
- Often, it would be harmful to evaluate y and z
- (and (not (= y 0)) (even? (quotient x y)))