World’s Tiniest Language

BrainF*ck is an esoteric language created in 1993 by Swiss physics student Urban Müller.  (Don’t blame me, I didn’t come up with the name!)  It consists of 8 instructions and is fully Turing-complete.  Here is a complete implementation in Algol-24:

var MEMORY_SIZE  := 65535;
var ScreenBuffer := '';

procedure Interpret(Code : String);
var
   Loop := 0;
   Instruction := 0;
   Memory := Buffer(MEMORY_SIZE, 0);

begin
   procedure Find(StartChar, EndChar, Increment);
   begin
      Instruction := Instruction + Increment;
      while Loop > 0 Or Code[Instruction] <> EndChar do
      begin
         if Code[Instruction] = StartChar then
            Loop := Loop + 1;
         else if Code[Instruction] = EndChar then
            Loop := Loop - 1;
         
         Instruction := Instruction + Increment;
      end
   end

   while Instruction < Length(Code) do
   begin
      var Value := Memory.GetValue();

      case Code[Instruction] of
         '>' : Memory.Advance();
         '<' : Memory.Rewind();
         '+' : Memory.SetValue(Value + 1);
         '-' : Memory.SetValue(Value - 1);
         '.' : ScreenBuffer := ScreenBuffer + Char(Value);
         '[' : if Value = 0 then Find('[', ']', 1);
         ']' : if Value <> 0 then Find(']', '[', -1);
      end
      Instruction := Instruction + 1;
   end
end

test 'Run BF Program';
begin
   var Code := '-[------->+<]>-.-[->+++++<]>++.+++++++..+++.[--->+<]>-----.' + 
      '---[->+++<]>.+++[->++++<]>+.++++++++++.+++[->+++<]>+.++++++++++++.-.' + 
      '+++++.----------.+++++.-[->+++++<]>.';
   Interpret(Code);

   AssertEqual('????? ??????????', ScreenBuffer);
end

Coming in 42 lines of code, it is truly tiny!  Lamborghini to the first person in the comments who can fill in the value to make the unit test pass 😀

******************************************

If you run this program:

[sierpinski.b -- display Sierpinski triangle
(c) 2016 Daniel B. Cristofani]
++++++++[>+>++++<<-]>++>>+<[-[>>+<<-]+>>]>+[-<<<[->[+[-]+>++>>>-<<]<[<]>>++++++[<<+++++>>-]+<<++.[-]<<]>.>+[>>]>+]

This is the output:

Pretty amazing, huh?