new files

Task/Ackermann-function/REXX/ackermann-function-1.rexx

@@ -0,0 +1,25 @@
+/*REXX program calculates/shows some values for the Ackermann function. */
+
+                     /*Note: the Ackermann function (as implemented) is */
+                     /*      higly recursive and is limited by the      */
+                     /*      biggest number that can have "1" added to  */
+                     /*      a number (successfully, accurately).       */
+high=24
+         do j=0 to 3;   say
+              do k=0 to high%(max(1,j))
+              call Ackermann_tell j,k
+              end   /*k*/
+         end        /*j*/
+exit                                   /*stick a fork in it, we're done.*/
+/*──────────────────────────────────ACKERMANN_TELL subroutine───────────*/
+ackermann_tell: parse arg mm,nn;   calls=0    /*display an echo message.*/
+nnn=right(nn,length(high))
+say 'Ackermann('mm","nnn')='right(ackermann(mm,nn),high),
+                             left('',12) 'calls='right(calls,high)
+return
+/*──────────────────────────────────ACKERMANN subroutine────────────────*/
+ackermann: procedure expose calls      /*compute the Ackerman function. */
+parse arg m,n;      calls=calls+1
+if m==0 then return n+1
+if n==0 then return ackermann(m-1,1)
+             return ackermann(m-1,ackermann(m,n-1))

Task/Ackermann-function/REXX/ackermann-function-2.rexx

@@ -0,0 +1,21 @@
+/*REXX program calculates/shows some values for the Ackermann function. */
+high=24
+         do j=0 to 3;   say
+              do k=0 to high%(max(1,j))
+              call Ackermann_tell j,k
+              end   /*k*/
+         end        /*j*/
+exit                                   /*stick a fork in it, we're done.*/
+/*──────────────────────────────────ACKERMANN_TELL subroutine───────────*/
+ackermann_tell: parse arg mm,nn;   calls=0    /*display an echo message.*/
+nnn=right(nn,length(high))
+say 'Ackermann('mm","nnn')='right(ackermann(mm,nn),high),
+                             left('',12) 'calls='right(calls,10)
+return
+/*──────────────────────────────────ACKERMANN subroutine────────────────*/
+ackermann: procedure expose calls      /*compute the Ackerman function. */
+parse arg m,n;      calls=calls+1
+if m==0 then return n+1
+if n==0 then return ackermann(m-1,1)
+if m==2 then return n*2+3
+             return ackermann(m-1,ackermann(m,n-1))

Task/Ackermann-function/REXX/ackermann-function-3.rexx

@@ -0,0 +1,36 @@
+/*REXX program calculates/shows some values for the Ackermann function. */
+high=24
+numeric digits 100        /*have REXX to use up to  100  digit integers.*/
+
+                          /*When REXX raises a number to a power  (via  */
+                          /*  the   **  operator), the power must be an */
+                          /*  integer  (positive,  zero,  or negative). */
+
+       do j=0 to 4;  say  /*Ackermann(5,1) is a bit impractical to calc.*/
+             do k=0 to high%(max(1,j))
+             call Ackermann_tell j,k
+             if j==4 & k==2 then leave    /*no sense in going overboard.*/
+             end   /*k*/
+       end         /*j*/
+exit                                   /*stick a fork in it, we're done.*/
+/*──────────────────────────────────ACKERMANN_TELL subroutine───────────*/
+ackermann_tell: parse arg mm,nn;   calls=0    /*display an echo message.*/
+nnn=right(nn,length(high))
+say 'Ackermann('mm","nnn')='right(ackermann(mm,nn),high),
+                             left('',12) 'calls='right(calls,10)
+return
+/*──────────────────────────────────ACKERMANN subroutine────────────────*/
+ackermann: procedure expose calls      /*compute the Ackerman function. */
+parse arg m,n;      calls=calls+1
+if m==0 then return n+1
+if m==1 then return n+2
+if m==2 then return n+n+3
+if m==3 then return 2**(n+3)-3
+if m==4 then do;  a=2
+                         do (n+3)-1     /*ugh!*/
+                         a=2**a
+                         end
+             return a-3
+             end
+if n==0 then return ackermann(m-1,1)
+             return ackermann(m-1,ackermann(m,n-1))