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@tenderlove
Created August 20, 2015 19:21
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l={};s=m=[];i=pc=mc=0
alias p proc
h={'>':p{mc+=1},'<':p{mc-=1},'+':p{m[mc]+=1},'-':p{m[mc]-=1},'.':p{putc m[mc]}}
j={'[':->(i){s<<i;->(){pc=l[pc-1]+1 if m[mc]==0}},']':->(i){o=s.pop;l[o]=i;p{pc=o}}}
ins=DATA.each_char.map{|c|c=:"#{c}";x=(j[c]||->(_){h[c]||p{}}).(i);i+=1;x}
while k=ins[pc];pc+=1;m[mc]||=0;k.();end
__END__
[ This program prints "Hello World!" and a newline to the screen, its
length is 106 active command characters. [It is not the shortest.]
This loop is a "comment loop", a simple way of adding a comment
to a BF program such that you don't have to worry about any command
characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
ignored, the "[" and "]" characters just have to be balanced. This
loop and the commands it contains are ignored because the current cell
defaults to a value of 0; the 0 value causes this loop to be skipped.
]
+++++ +++ Set Cell #0 to 8
[
>++++ Add 4 to Cell #1; this will always set Cell #1 to 4
[ as the cell will be cleared by the loop
>++ Add 2 to Cell #2
>+++ Add 3 to Cell #3
>+++ Add 3 to Cell #4
>+ Add 1 to Cell #5
<<<<- Decrement the loop counter in Cell #1
] Loop till Cell #1 is zero; number of iterations is 4
>+ Add 1 to Cell #2
>+ Add 1 to Cell #3
>- Subtract 1 from Cell #4
>>+ Add 1 to Cell #6
[<] Move back to the first zero cell you find; this will
be Cell #1 which was cleared by the previous loop
<- Decrement the loop Counter in Cell #0
] Loop till Cell #0 is zero; number of iterations is 8
The result of this is:
Cell No : 0 1 2 3 4 5 6
Contents: 0 0 72 104 88 32 8
Pointer : ^
>>. Cell #2 has value 72 which is 'H'
>---. Subtract 3 from Cell #3 to get 101 which is 'e'
+++++++..+++. Likewise for 'llo' from Cell #3
>>. Cell #5 is 32 for the space
<-. Subtract 1 from Cell #4 for 87 to give a 'W'
<. Cell #3 was set to 'o' from the end of 'Hello'
+++.------.--------. Cell #3 for 'rl' and 'd'
>>+. Add 1 to Cell #5 gives us an exclamation point
>++. And finally a newline from Cell #6
@googya
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googya commented Aug 21, 2015

Nice

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