Brainfuck

• Fast Brainfuck interpreter bff4.c
  I have compared speed with fast bff.c interprer. Time required to run a program is in the table below.

  bff bff4 bff4lnr long.b Linux GCC 27.30 30.85 10.15 Cygwin GCC 25.90 21.80 12.11 MS compiler 24.10 19.70 9.60 si ! si ! hi123 Linux GCC 22.77 32.74 22.25 Cygwin GCC 28.80 21.70 34.05 MS compiler 21.90 19.50 18.70

  Comments bff - is bff.c by Alex Pankratov bff4 - is bff4.c compiled with -DNOLNR to disable linear optimisation bff4lnr - is bff4.c with linear optimisation (default) of linear loops (loops with balanced < and >); for example [>++<-] long.b is a dummy program. It takes time to run it. si is Daniel's self-interpreter hi123.b is a dummy program printing hello123. This program is written in dbfi dialect (input is given to the program after !) si ! si ! hi123 - is a two level stack of self-interpreters. Command to bff is cat si ! hi123 | bff si where '!' is a file having only one byte '!'. Command to bff4 is cat si ! si ! hi123 | bff4 Tested with: GCC flags [-O3 -ansi -DNDEBUG] cygwin GCC version 3.4.4, linux GCC version 4.0.0, MS flags [-Ox] compiler version 13.00

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• Brainfuck interpreter (DBFI dialect) stackbfi.c, written in standard C. It uses neither global memory allocation nor dynamic malloc. The stack is its BF memory field.

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• Brainfuck Online Debugger self-interpreter

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• A paper (PDF) (in Russian) describing Daniel B. Cristofani's a short self-interpreter, based on a simplistic Turing-complete imperative language - brainfuck dialect. This interpreter explicitly processes the statements of the language, which means the interpreter constitutes a description of the language inside that same language. The paper does not require any specific knowledge; however, experience in programming and a vivid imagination are beneficial.

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• Base expansion: the technique to expand a value. It is quite general. One can expand by any base and with different layout - (0 : N-1), or (1 : N), or (0 : N-1)+1. Here noted
  (0 : N-1) a usual expansion, like 5 binary is 101;
  (1 : N) an expansion where zeros take over the higher digit, e.g. 1 2 3 4 5 6 7 8 ... binary are 1, 2, 11, 12, 21, 22, 111, 112, ... ;
  (0 : N-1)+1 is a usual expansion where every digit is incremented by 1.

  The second and the third cases may especially be useful for brainfuck since sometimes it is not desirable to have zeros.

  The technique can be seen in this example:

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

  This is the expansion on base 7 with the second case (1 : N).

  The third case is used for a program printing decimal ASCII values of the input characters.

  -----------------------------------------------
  this program prints ascii values of input chars
  >>,
  [
    [ -<++> 
    [ -<+> 
      [ -<+> 
        [ -<+> 
          [ -<+> 
            [ -<+> 
              [ -<+> 
                [ -<+> 
                  [ -<+> 
                    [ <[-]+> ->+< [<-] ]
    ]]]]]]]] >] 
  
  print digits
  <<[>++++++[<++++++++>-]<-.[-]<]
  
  print eol
  ++++++++++.[-]>>
  ,]
  -----------------------------------------------
  

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• Daniel's binary expansion [[>]+<[-<]>] (turns {0 'x 0 0 0 0} into {0 '0 b b b b})

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• Case statement in brainfuck.

  start with 0 1 'x
  >+>++
  [
      -[
          -[
              -[
                  [-]
                  <- case 4 or more <,.> >
              ]
              <[- case 3 <,+.> ]>
          ]
          <[- case 2 <,++.> ]>
      ]
      <[- case 1 <,+++.> ]>
  ]
  <[- case 0 <,++++.> ]>
  

  This program will double increment the input character executing 'case 2'.

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• Program which outputs 202 (very short)
  >+>+>+>+>++<[>[<+++>-]<<]>.

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• See also http://code.google.com/p/mazonka/source/browse/trunk/mazgoo/bff4/

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