34 lines
1.5 KiB
Forth
Executable File
34 lines
1.5 KiB
Forth
Executable File
( The Towers Of Hanoi )
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( FORTH )
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( Copyright 1998 Amit Singh. All Rights Reserved. )
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( http://hanoi.kernelthread.com )
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( )
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( Tested under GNU Forth 0.3.0, PFE 0.9.14 )
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( Use "gforth <thisfile> -e 'n HANOI bye'" to run )
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( hanoi with n disks. Alternatively, load everything )
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( and use the HANOI word from within the interpreter. )
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: MOVEIT ." move " . ." --> " . CR ; ( to from -- )
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: DOHANOI ( to from using n -- )
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( T3 <- T1 using T2 )
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DUP 0 > ( more disks ? )
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IF
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1 - ( n <- n - 1 )
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2OVER 2OVER ( clone data stack )
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>r >r >r >r ( save it to rstack )
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1 ROLL 2 ROLL 3 ROLL 3 ROLL ( using from to n-1 )
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RECURSE ( T2 <- T1 using T3 )
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2r@ SWAP MOVEIT ( to from )
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2DROP 2DROP ( empty the stack )
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2r> 2r> ( from to n-1 using )
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SWAP ( from to using n-1 )
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3 ROLL ( to using n-1 from )
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SWAP ( to using from n-1 )
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RECURSE ( T3 <- T2 using T1 )
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THEN ;
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: HANOI ( n -- ) ( prepare arguments )
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3 1 2 3 ROLL DOHANOI 2DROP 2DROP ;
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