Family Day update

Task/Queue-Definition/Factor/queue-definition.factor

@@ -0,0 +1,18 @@
+USING: accessors kernel ;
+IN: rosetta-code.queue-definition
+
+TUPLE: queue head tail ;
+TUPLE: node value next ;
+
+: <queue> ( -- queue ) queue new ;
+: <node> ( obj -- node ) node new swap >>value ;
+
+: empty? ( queue -- ? ) head>> >boolean not ;
+
+: enqueue ( obj queue -- )
+    [ <node> ] dip 2dup dup empty?
+    [ head<< ] [ tail>> next<< ] if tail<< ;
+
+: dequeue ( queue -- obj )
+    dup empty? [ "Cannot dequeue empty queue." throw ] when
+    [ head>> value>> ] [ head>> next>> ] [ head<< ] tri ;