Data commit

Task/Farey-sequence/Common-Lisp/farey-sequence.lisp

@@ -0,0 +1,20 @@
+(defun farey (n)
+  (labels ((helper (begin end)
+	     (let ((med (/ (+ (numerator begin) (numerator end))
+			   (+ (denominator begin) (denominator end)))))
+	       (if (<= (denominator med) n)
+		   (append (helper begin med)
+			   (list med)
+			   (helper med end))))))
+      (append (list 0) (helper 0 1) (list 1))))
+
+
+;; Force printing of integers in X/1 format
+(defun print-ratio (stream object &optional colonp at-sign-p)
+  (format stream "~d/~d" (numerator object) (denominator object)))
+
+(loop for i from 1 to 11 do
+     (format t "~a: ~{~/print-ratio/ ~}~%" i (farey i)))
+
+(loop for i from 100 to 1001 by 100 do
+     (format t "Farey sequence of order ~a has ~a terms.~%" i (length (farey i))))