26 lines
2.2 KiB
Rexx
26 lines
2.2 KiB
Rexx
/*REXX program calculates and displays some values for the Ackermann function. */
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/*╔════════════════════════════════════════════════════════════════════════╗
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║ Note: the Ackermann function (as implemented here) utilizes deep ║
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║ recursive and is limited by the largest number that can have ║
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║ "1" (unity) added to a number (successfully and accurately). ║
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╚════════════════════════════════════════════════════════════════════════╝*/
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high=24
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do j=0 to 3; say
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do k=0 to high % (max(1, j))
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call tell_Ack j, k
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end /*k*/
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end /*j*/
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exit /*stick a fork in it, we're all done. */
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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tell_Ack: parse arg mm,nn; calls=0 /*display an echo message to terminal. */
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#=right(nn,length(high))
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say 'Ackermann('mm", "#')='right(ackermann(mm, nn), high),
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left('', 12) 'calls='right(calls, high)
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return
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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ackermann: procedure expose calls /*compute value of Ackermann function. */
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parse arg m,n; calls=calls+1
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if m==0 then return n+1
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if n==0 then return ackermann(m-1, 1)
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return ackermann(m-1, ackermann(m, n-1) )
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