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+;;;; "ratize.scm" Convert number to rational number
+
+(define (rational:simplest x y)
+ (define (sr x y) (let ((fx (floor x)) (fy (floor y)))
+ (cond ((not (< fx x)) fx)
+ ((= fx fy) (+ fx (/ (sr (/ (- y fy)) (/ (- x fx))))))
+ (else (+ 1 fx)))))
+ (cond ((< y x) (rational:simplest y x))
+ ((not (< x y)) (if (rational? x) x (slib:error)))
+ ((positive? x) (sr x y))
+ ((negative? y) (- (sr (- y) (- x))))
+ (else (if (and (exact? x) (exact? y)) 0 0.0))))
+(define (rationalize x e) (rational:simplest (- x e) (+ x e)))