Tag: brainfuck

Delphi: Basic Brainfuck Interpreter

Frédéric Hannes

This is a really basic commandline brainfuck interpreter, it’s not written for speed or performance, it just shows you how a brainfuck interpreter should work. Of course you can speed it up by converting the code to a form of bytecode, working with pointers or even convert it to machine code.

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001program Brainfuck;
002 
003{$APPTYPE CONSOLE}
004 
005uses
006  Classes;
007 
008const
009  ARRAY_SIZE = 30000;
010 
011type
012  TBFEngine = class
013  private
014    FScript: TStrings;
015    FCompiled: AnsiString;
016    FArr: array of Byte;
017    FIndex: Integer;
018    procedure Compile;
019    procedure ClearArray;
020  public
021    constructor Create;
022    destructor Destroy; override;
023    procedure Run;
024    property Script: TStrings read FScript;
025  end;
026 
027{ TBFEngine }
028 
029procedure TBFEngine.ClearArray;
030var
031  i, l: Integer;
032begin
033  l := Length(FArr);
034  for i := 0 to l - 1 do
035    FArr[i] := 0;
036end;
037 
038procedure TBFEngine.Compile;
039var
040  i, l: Integer;
041begin
042  l := Length(FScript.Text);
043  FCompiled := '';
044  for i := 1 to l do
045    if FScript.Text[i] in ['>', '<', '+', '-', '.', ',', '[', ']'] then
046      FCompiled := FCompiled + FScript.Text[i];
047end;
048 
049constructor TBFEngine.Create;
050begin
051  FScript := TStringList.Create;
052  SetLength(FArr, ARRAY_SIZE);
053end;
054 
055destructor TBFEngine.Destroy;
056begin
057  FScript.Free;
058end;
059 
060procedure TBFEngine.Run;
061var
062  c: AnsiChar;
063  i, j, l, t: Integer;
064begin
065  Compile;
066  ClearArray;
067  t := 0;
068  FIndex := 0;
069  l := Length(FCompiled);
070  i := 1;
071  while i <= l do
072  begin
073    case FCompiled[i] of
074      '>':
075        if FIndex <> (ARRAY_SIZE - 1) then
076          Inc(FIndex);
077      '<':
078        if FIndex <> 0 then
079          Dec(FIndex);
080      '+': Inc(FArr[FIndex]);
081      '-': Dec(FArr[FIndex]);
082      '.': Write(Chr(FArr[FIndex]));
083      ',': Read(FArr[FIndex]);
084      '[':
085        if not Boolean(FArr[FIndex]) then
086          for j := i + 1 to l do
087          begin
088            c := FCompiled[j];
089            if c = '[' then
090              Inc(t)
091            else if c = ']' then
092              if t <> 0 then
093                Dec(t)
094              else begin
095                i := j;
096                Break;
097              end;
098          end;
099      ']':
100        if Boolean(FArr[FIndex]) then
101          for j := i - 1 downto 1 do
102          begin
103            c := FCompiled[j];
104            if c = ']' then
105              Inc(t)
106            else if c = '[' then
107              if t <> 0 then
108                Dec(t)
109              else begin
110                i := j;
111                Break;
112              end;
113          end;
114    end;
115    Inc(i);
116  end;
117end;
118 
119var
120  Engine: TBFEngine;
121begin
122  if ParamCount = 1 then
123  begin
124    Engine := TBFEngine.Create;
125    Engine.Script.LoadFromFile(ParamStr(1));
126    Engine.Run;
127    Engine.Free;
128  end;
129end.

Hello world in brainfuck:
++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.——.——–.>+.>.

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