September 2017 Update

Task/Associative-array-Iteration/Ol/associative-array-iteration.ol

@@ -0,0 +1,58 @@
+;;; create sample associative array
+(define aa (list->ff '(
+   (hello . 1)
+   (world . 2)
+   (! . 3))))
+
+(print aa)
+; ==> #((! . 3) (hello . 1) (world . 2))
+
+;;; simplest iteration over all associative array (using ff-iter, lazy iterator)
+(let loop ((kv (ff-iter aa)))
+   (cond
+      ((null? kv) #true)
+      ((pair? kv)
+         (print (car kv))
+         (loop (cdr kv)))
+      (else (loop (force kv)))))
+; ==> (! . 3)
+; ==> (hello . 1)
+; ==> (world . 2)
+
+;;; iteration with returning value (using ff-fold)
+(print
+   "folding result: "
+   (ff-fold
+      (lambda (result key value)
+         (print "key: " key ", value: " value)
+         (+ result 1))
+      0
+      aa))
+
+; ==> key: !, value: 3
+; ==> key: hello, value: 1
+; ==> key: world, value: 2
+; ==> folding result: 3
+
+;;; same but right fold (using ff-foldr)
+(print
+   "rfolding result: "
+   (ff-foldr
+      (lambda (result key value)
+         (print "key: " key ", value: " value)
+         (+ result 1))
+      0
+      aa))
+
+; ==> key: world, value: 2
+; ==> key: hello, value: 1
+; ==> key: !, value: 3
+; ==> rfolding result: 3
+
+;;; at least create new array from existing (let's multiply every value by value)
+(define bb (ff-map aa
+      (lambda (key value)
+         (* value value))))
+(print bb)
+
+; ==> #((! . 9) (hello . 1) (world . 4))