What is wrong with this recursive Windows CMD script? It won't do Ackermann properly
- by boost
I've got this code that I'm trying to get to calculate the Ackermann function so that I can post it up on RosettaCode. It almost works. I thought maybe there'd be a few batch file wizards on StackOverflow.
::echo off
set depth=0
:ack
if %1==0 goto m0
if %2==0 goto n0
:else
set /a n=%2-1
set /a depth+=1
call :ack %1 %n%
set t=%errorlevel%
set /a depth-=1
set /a m=%1-1
set /a depth+=1
call :ack %m% %t%
set t=%errorlevel%
set /a depth-=1
if %depth%==0 ( exit %t% ) else ( exit /b %t% )
:m0
set/a n=%2+1
if %depth%==0 ( exit %n% ) else ( exit /b %n% )
:n0
set /a m=%1-1
set /a depth+=1
call :ack %m% %2
set t=%errorlevel%
set /a depth-=1
if %depth%==0 ( exit %t% ) else ( exit /b %t% )
I use this script to test it
@echo off
cmd/c ackermann.cmd %1 %2
echo Ackermann of %1 %2 is %errorlevel%
A sample output, for Test 1 1, gives:
>test 1 1
>set depth=0
>if 1 == 0 goto m0
>if 1 == 0 goto n0
>set /a n=1-1
>set /a depth+=1
>call :ack 1 0
>if 1 == 0 goto m0
>if 0 == 0 goto n0
>set /a m=1-1
>set /a depth+=1
>call :ack 0 0
>if 0 == 0 goto m0
>set/a n=0+1
>if 2 == 0 (exit 1 ) else (exit /b 1 )
>set t=1
>set /a depth-=1
>if 1 == 0 (exit 1 ) else (exit /b 1 )
>set t=1
>set /a depth-=1
>set /a m=1-1
>set /a depth+=1
>call :ack 0 1
>if 0 == 0 goto m0
>set/a n=1+1
>if 1 == 0 (exit 2 ) else (exit /b 2 )
>set t=2
>set /a depth-=1
>if 0 == 0 (exit 2 ) else (exit /b 2 )
Ackermann of 1 1 is 2
