langs a-z

Task/Apply-a-callback-to-an-array/REBOL/apply-a-callback-to-an-array.rebol

@@ -0,0 +1,28 @@
+REBOL [
+    Title: "Array Callback"
+    Date: 2010-01-04
+    Author: oofoe
+    URL: http://rosettacode.org/wiki/Apply_a_callback_to_an_Array
+]
+
+map: func [
+	"Apply a function across an array."
+	f [native! function!] "Function to apply to each element of array."
+	a [block!] "Array to process."
+	/local x
+][x: copy []  forall a [append x do [f a/1]]  x]
+
+square: func [x][x * x]
+
+; Tests:
+
+assert: func [code][print [either do code ["  ok"]["FAIL"]  mold code]]
+
+print "Simple loop, modify in place:"
+assert [[1 100 81] = (a: [1 10 9]  forall a [a/1: square a/1]  a)]
+
+print [crlf "Functional style with 'map':"]
+assert [[4 16 36] = map :square [2 4 6]]
+
+print [crlf "Applying native function with 'map':"]
+assert [[2 4 6] = map :square-root [4 16 36]]