Data update

Task/Recamans-sequence/Rebol/recamans-sequence.rebol

@@ -0,0 +1,31 @@
+Rebol [
+    title: "Rosetta code: Recaman's sequence"
+    file:  %Recaman's_sequence.r3
+    url:   https://rosettacode.org/wiki/Recaman%27s_sequence
+]
+
+recaman-until: function/with [code [block!]][
+    r: 0 n: 1
+    result: reduce [r] ;; result sequence
+    seen:   reduce [r] ;; set of visited values for O(1) duplicate check
+    bind code 'n
+    until [
+        append result r: recaman-succ seen n r
+        if new?: not find seen r [ append seen r ]
+        ++ n
+        do code        ;; evaluate stop condition with current n in scope
+    ]
+    result
+][
+    recaman-succ: function [seen [block!] n [integer!] r [integer!]][
+        back: r - n
+        ;; go back if positive and not already seen, otherwise go forward
+        either any [back < 0  find seen back] [r + n] [back]
+    ]
+]
+
+print "First 15 Recaman numbers:"
+print recaman-until [n = 15]
+print ""
+print "First duplicate Recaman number:"
+print last recaman-until [not new?]