SICP 연습문제 풀이 1.20

(gcd 206 40) In normal order evaluation

=>(if (= 40 0)
      206
      (gcd 40 (remainder 206 40)))

=>(gcd 40 (remainder 206 40))

=>(if (= (remainder 206 40) 0)
      40
      (gcd (remainder 206 40) (remainder 40 (remainder 206 40))))

=>(gcd (remainder 206 40) (remainder 40 (remainder 206 40)))

=>(if (= (remainder 40 (remainder 206 40)) 0)
      (remainder 206 40)
      (gcd (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))))

=>(gcd (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40))))

=>(if (= (remainder (remainder 206 40) (remainder 40 (remainder 206 40))) 0)
      (remainder 40 (remainder 206 40))
      (gcd (remainder (remainder 206 40) (remainder 40 (remainder 206 40))) (remainder (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40))))))

=>(gcd (remainder (remainder 206 40) (remainder 40 (remainder 206 40))) (remainder (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))))

=>(if (= (remainder (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))) 0)
      (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))
      (gcd (remainder (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))) (remainder (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))
   (remainder (remainder 40 (remainder 206 40)) (remainder (remainder 206 40) (remainder 40 (remainder 206 40)))))))

=>(remainder (remainder 206 40) (remainder 40 (remainder 206 40)))

remainder 는 총 18 번 수행된다.

(gcd 206 40) In normal order evaluation

(gcd 206 40)

=>(if (= 40 0)
      206
      (gcd 40 (remainder 206 40)))

=>(gcd 40 (remainder 206 40))

=>(gcd 40 6)

=>(if (= 6 0)
      40
      (gcd 6 (remainder 40 6)))

=>(gcd 6 (remainder 40 6))

=>(gcd 6 4)

=>(if (= 4 0)
      6
      (gcd 4 (remainder 6 4)))

=>(gcd 4 (remainder 6 4))

=>(gcd 4 2)

=>(if (= 2 0)
      4
      (gcd 2 (remainder 4 2 )))

=>(gcd 2 (remainder 4 2 ))

=>(gcd 2 0)

=>(if (= 0 0)
      2
      (gcd 0 (remainder 2 0)))

=> 2

remainder 는 총 4 번 수행된다.