Data commit

Task/Periodic-table/Scheme/periodic-table-1.ss

@@ -0,0 +1,39 @@
+(define (position-increment n)
+  (cond
+   ((= n   1) '( 0 .  17))
+   ((= n   2) '( 1 . -17))
+   ((= n   4) '( 0 .  11))
+   ((= n  10) '( 1 . -17))
+   ((= n  12) '( 0 .  11))
+   ((= n  18) '( 1 . -17))
+   ((= n  36) '( 1 . -17))
+   ((= n  54) '( 1 . -17))
+   ((= n  56) '( 2 .   2))
+   ((= n  71) '(-2 . -14))
+   ((= n  86) '( 1 . -17))
+   ((= n  88) '( 2 .   2))
+   ((= n 103) '(-2 . -14))
+   (else      '( 0 .   1))))
+
+(define (move p i)
+  (cons (+ (car p) (car i))
+        (+ (cdr p) (cdr i))))
+
+(define (position n)
+  (if (= n 1)
+      '(1 . 1)
+      (let ((m (- n 1)))
+        (move (position m)
+              (position-increment m)))))
+
+(define (format-line n p)
+  (display n)
+  (display " -> ")
+  (display (car p))
+  (display " ")
+  (display (cdr p))
+  (newline))
+
+(for-each (lambda (n)
+            (format-line n (position n)))
+          (list 1 2 29 42 57 58 72 89))

Task/Periodic-table/Scheme/periodic-table-2.ss

@@ -0,0 +1,9 @@
+(define position*
+  (let ((memo (make-vector 118 #f)))
+    (lambda (n)
+      (let* ((mi (- n 1))
+             (mp (vector-ref memo mi)))
+        (or mp
+            (let ((p (position n)))
+              (vector-set! memo mi p)
+              p))))))