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- ; use newtons better approximation formula
- ; (x / y^2 + 2y) / 3
- (define (sqrt-iter prev-guess guess x)
- ; util procs
- (define (square x) (* x x))
- ; ??? somehow throws up invalid values
- (define (approx g)
- (/ (+ (/ x (square g))
- (* 2 g))
- 3))
- (define (delta prev-guess guess)
- (abs (- prev-guess guess)))
- ; body
- (if (< (delta prev-guess guess) (* prev-guess 0.0000001))
- guess
- (sqrt-iter guess (approx guess) x)))
- (define (sqrt x) (sqrt-iter 0. 1. x))
- 3 (sqrt 3)
- 4 (sqrt 4)
- 9 (sqrt 9)
- 100 (sqrt 100)
- 400000000 (sqrt 400000000)
- 0.1 (sqrt 0.1)
- 0.0000001 (sqrt 0.0000001)
- 123456789123456789 (sqrt 123456789123456789)
- .98765432198765432 (sqrt .98765432198765432)
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