logical branflakes competition results (1994)

The contest was to make a branflakes program which could compute and output the
value of any valid expression formed of bitwise logical operators (acting on
bytes) and numerical constants. The expressions were input in reverse Polish
notation, using the C characters for bitwise operators ~&^|. The constants
were to be input in decimal, and separated by commas where necessary; at every
linefeed, the expression immediately preceding it is to be output, but
linefeeds do not otherwise interrupt expressions (they don't clear the stack).

Only one person finished an entry by the deadline: LV, with the
following very well-constructed program. Thus he was declared the winner.



In short: get an input byte; write it in binary; determine what
input byte it was by jumping at meaningful bit positions; Then
according to the input byte do different actions
  NOT:  compute 255 minus number
  LINEFEED: print the number in decimal
  COMMA: just push a number on the stack
  DIGIT: multiply previous number by ten and add digit to it
  OR; AND; XOR: store the number of binary operation to do later
If there is an operation number at the end: then perform the
binary operation: expand both numbers in binary with digits interweaved;
then make a pass over them two bits at a time; finally reconstruct the
result

>,[

  structure is:  nux
                   ^
  where n = number on top of stack;
        u = 0 if not inside a number; 1 if in a number
        x = next input byte

  nux000000000
    ^

  write the input byte in binary
  [>>[>]+<[-<]<-]

  nu00lxxxxxxh
    ^
  >>

  01010000 (nl) | 01100100 (&) | 00110100 (co) | xxxx1100
  ^               ^              ^               ^
  01111010 (^)  | 00111110 (|) | 01111110 (~)
  ^               ^              ^

  >>>>
  01010000 (nl) | 01100100 (&) | 00110100 (co) |
      ^               ^              ^
  xxxx1100  | 01111010 (^)  | 00111110 (|) | 01111110 (~)
      ^           ^               ^              ^
  [
    >>
  xxxx1100  | 01111010 (^)  | 00111110 (|) | 01111110 (~)
        ^           ^               ^              ^
    [
  01111010 (^)  | 00111110 (|) | 01111110 (~)
        ^               ^              ^
      -<
  01111000 (^)  | 00111100 (|) | 01111100 (~)
       ^               ^              ^
      [<<<<
  00111100 (|) | 01111100 (~)
   ^              ^
        [  this is the NOT case

          nu00 01111100 (~)
                ^

          compute 255
          <+<+[>]+[>[-<++>]<<]

          nu0z 00000000   (z=255)
            ^
          <[-]<[->>>-<<<]>>>[-<<<+>>>]
          mu00 00000000
             ^
        ]>
  nu00 00111100 (|) | mu00 000000
         ^                 ^
        [  OR case
          strip the ones
          [>]<[-<]

          abu00 00000000
                 ^
          +<
        ]
   abu00 010      | mu00 000
         ^               ^
      ]<

   abu00 01111000 (^)  | abu00 010 | mu00 000
             ^               ^          ^
      [ XOR case; strip the ones
        [-<]>++<<
      ]

   abu00 020  | abu00 010 | mu00 000
       ^            ^          ^
   ]<

   nu00 xxxx1100  | abu00 020  | abu00 010 | mu00 000
             ^         ^            ^          ^
   [ digit

     -<++[<[-<++>]>[-<+>]<-]

     nu00 d0    (d = digit)
           ^
     <<<<
     nu00 d0
      ^
     [ if u==1 then we accumulate to the next number
       -<
       [->++<]>[->>+++++<<]

       000N d
        ^
       >>>[-<+>]<<<<
       000m 0
       ^
     ]
     n000 d  | 000 m
      ^        ^

     >+>>[-<<<+>>>]
     m100
        ^
     <
   ]

   mu00 000  | abu00 020  | abu00 010 | mu00 000
     ^            ^            ^          ^

   >

   mu00 000  | abu00 0o0
      ^            ^

  ]>

  01010000 (nl) | 01100100 (&) | 00110100 (co) | mu00 000  | abu00 0o0
       ^               ^              ^               ^            ^

  [
    abu00 01100100 (&) | nu00 00110100 (co)
               ^                   ^
    -<<
    abu00 01100000 (&) | nu00 00110000 (co)
             ^                   ^

    [ comma
      remove ones

      -<-<
      n100 00000000
            ^

      clear u field
      <<<<->>>

      nu00 000
           ^
    ]<
    abu00 01100000 (&) | mu00 000
            ^               ^
    [ AND
      -<++<<
    ]
    abu00 030 | mu00 000
        ^          ^
    >
  ]

  01010000 (nl) | mu00 000  | abu00 0o0
       ^               ^            ^
  <<
  01010000 (nl) | mu00 000  | abu00 0o0
     ^              ^            ^
  [ LINEFEED: print the number

    nu00 01010000
            ^
    [-<<]<<[-]<

    n
    ^
    copy n

    [->+>+<<]
    0nn
    ^
    >[-<+>]>
    n0n0
      ^
    [ if n is not zero
      [ for the quotient
        [ number  n a q 0 0
          ->>+<[->]>[<+++++++++>>>]<<<<
        ] 0 r q 0 0
        >
        [<+++++ +++++>[-<->]>-<]
        +>
      ]
      <[<<]
    ]
    <[>]
    >>[-]+[>>]<<
    [+++++++[-<++++++>]<.[-]<]
    +++++ +++++.[-]

    n0
     ^
    >
    nu00
      ^
  ]

  mu00 000  | abu00 0o0
    ^            ^
  >>>
  mu00 000  | abu00 0o0
        ^            ^
  [ binary operation!

    abu00 0o0
           ^

    [-<<<+>>>]<<<<[-]+>

    ab1o0
       ^


    [-<<[>>>>>>[>>]+<<[-<<]<<<<-]>]



      bxx000  | a0xx000x
      ^         ^



    000o00ababab
     ^
    >>[->+<]++++++++
    0008o0ababab
       ^
    [-
      io0ab
      ^
      >>+>>[-<+>]<<<
      io1s0
       ^

      i01s0 (or) | i11s0 (xor) | i21s0 (and)
       ^            ^             ^
      [-
        i01s0 (xor) | i11s0 (and)
         ^             ^
        [->->

          i00s0 (and)
             ^
          [-[->+<]]
          i000r
             ^
          ++<<
          i002r
           ^

        ]>
        i01s0 (xor) | i00or
          ^             ^
        [
          i01s0 (xor)
            ^
          ->[->+<[->-<]]+<
          i00or
            ^
        ]<
        i00or
         ^
      ]>

      i01s0 (or) | i00or
        ^            ^
      [->
        i00s0
           ^
        [>+<[-]]<
        i00or
          ^
      ]
      <<[->>+<<]>+>>>[-<<<<+>>>>]<<
      r1io0
        ^
    ]
    0000r1r1r1r1r1r1r1r10o
                        ^
    >[-]<<[->[-<<++>>]<<<]

    000n
      ^
    >[-<<<+>>>]
    n000
       ^
    >>
    mu00 000
          ^
  ]
  <<<,
]