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Member "FreeBASIC-1.09.0-win64/examples/manual/proguide/recursion_iteration/ackermann.bas" (1 Jan 2022, 1640 Bytes) of package /windows/misc/FreeBASIC-1.09.0-win64.zip:

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    1 '' examples/manual/proguide/recursion_iteration/ackermann.bas
    2 ''
    3 '' NOTICE: This file is part of the FreeBASIC Compiler package and can't
    4 ''         be included in other distributions without authorization.
    5 ''
    6 '' See Also: https://www.freebasic.net/wiki/wikka.php?wakka=ProPgRecursionIteration
    7 '' --------
    8 
    9 Function recursiveAckermann (ByVal m As Integer, ByVal n As Integer) As Integer
   10     If m = 0 Then
   11         Return n + 1
   12     Else
   13         If n = 0 Then
   14             Return recursiveAckermann(m - 1, 1)
   15         Else
   16             Return recursiveAckermann(m - 1, recursiveAckermann(m, n - 1))
   17         End If
   18     End If
   19 End Function
   20 
   21 #include "DynamicUserStackTypeCreateMacro.bi"
   22 DynamicUserStackTypeCreate(DynamicUserStackTypeForInteger, Integer)
   23 
   24 Function iterativeAckermann (ByVal m As Integer, ByVal n As Integer) As Integer
   25     Dim As DynamicUserStackTypeForInteger Sm, Sn
   26     Sm.push = m : Sn.push = n
   27     While Sm.used > 0
   28         m = Sm.pop : n = Sn.pop
   29         If m = 0 Then
   30             Sn.push = n + 1                                      ' Return n + 1 (and because of nested call)
   31         Else
   32             If n = 0 Then
   33                 Sm.push = m - 1 : Sn.push = 1                    ' Return Ackermann(m - 1, 1)
   34             Else
   35                 Sm.push = m - 1 : Sm.push = m : Sn.push = n - 1  ' Return Ackermann(m - 1, Ackermann(m, n - 1))
   36             End If
   37         End If
   38     Wend
   39     Return Sn.pop                                                ' (because of Sn.push = n + 1)
   40 End Function
   41 
   42 
   43 
   44 Print recursiveAckermann(3, 0), recursiveAckermann(3, 1), recursiveAckermann(3, 2), recursiveAckermann(3, 3), recursiveAckermann(3, 4)
   45 Print iterativeAckermann(3, 0), iterativeAckermann(3, 1), iterativeAckermann(3, 2), iterativeAckermann(3, 3), iterativeAckermann(3, 4)
   46 
   47 Sleep
   48