Add iter2lazy and lazy2iter

examples/lazyseqs.dst

@@ -62,7 +62,7 @@ body once, and then memoizes the result."
  (range2 0 end))
 
 (defn map
- "Return a sequence that is the result of apply f to each value in s."
+ "Return a sequence that is the result of applying f to each value in s."
  [f s]
  (delay
   (def x (s))
@@ -105,3 +105,39 @@ body once, and then memoizes the result."
   (when x
    (def thehead (get HEAD x))
    (if thehead (tuple thehead (take-while pred (get TAIL x)))))))
+
+#Iterators is a conscept that looks a lot like lazy seq
+#The following functions turn iterators to lazy seq and vice versa
+
+(defn- iter-self
+  [next]
+  (delay (tuple (next) (iter-self next))))
+
+(defn iter2lazy
+"Create a lazy sequence froma an iterator"
+  [iter]
+  (def  {:more more :next next} iter)
+  (iter-self next))
+
+(defn lazy2iter
+"turn a lazy-seq to an iterator"
+  [lazy-seq]
+  (var state lazy-seq)
+  {:more  state
+   :next (fn []     (def result (head state) )
+                    (def rest  (tail state))
+                    (if rest
+                      (:= state rest))
+                    result)})
+
+
+#Now we can use the nonfuctional filter from boot.dst
+#to write a filter version that returns a lazy sequence
+
+
+(defn filter2 [pred coll]
+  (tail (iter2lazy (filter pred coll))))
+
+
+
+