iterative ackermann

2007-11-08  Paolo Bonzini  <bonzini@gnu.org>

	* tests/ackermann.st: Add "iterative" implementation.

git-archimport-id: bonzini@gnu.org--2004b/smalltalk--devo--2.2--patch-629

ChangeLog

@@ -1,3 +1,7 @@
+2007-11-08  Paolo Bonzini  <bonzini@gnu.org>
+
+	* tests/ackermann.st: Add "iterative" implementation.
+
 2007-11-07  Paolo Bonzini  <bonzini@gnu.org>
 
 	* examples/Methods.st: Add brackets around compiled methods.

tests/ackermann.st

@@ -34,13 +34,34 @@ Integer extend [
         n = 0 ifTrue: [ ^self - 1 ack: 1 ].
         ^self - 1 ack: (self ack: n - 1)
     ]
+
+    ackIt: nn [
+	| n |
+	^[
+	    | m stack |
+	    m := self. n := nn.
+	    stack := OrderedCollection new.
+	    [ m = 0
+		ifTrue: [
+		    n := n + 1.
+		    m := stack removeLast ]
+		ifFalse: [
+		    n = 0
+			ifTrue: [
+			    m := m - 1.
+			    n := 1 ]
+			ifFalse: [
+			    stack addLast: m - 1.
+			    n := n - 1 ] ]
+	    ] repeat
+	] on: Error do: [ :ex | ex return: n ]
+    ]
 ]
 
 Eval [
     n := Smalltalk arguments isEmpty
 	ifTrue: [ 4 ]
 	ifFalse: [ Smalltalk arguments first asInteger ].
 
-    ('Ack(3,%1): %2' % { n. (3 ack: n) }) displayNl
-
+    ('Ack(3,%1): %2' % { n. (3 ack: n) }) displayNl.
 ]