From 52b8f7f0357194ecfe82ef063e579a3af7e1bd07 Mon Sep 17 00:00:00 2001
From: Jens Luedicke <jens.luedicke@gmail.com>
Date: Sun, 1 Feb 2015 12:30:23 +0100
Subject: [PATCH] Initial commit.

---
 brainfuck.erl | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++
 hello.bf      |   2 +
 2 files changed, 145 insertions(+)
 create mode 100644 brainfuck.erl
 create mode 100644 hello.bf

diff --git a/brainfuck.erl b/brainfuck.erl
new file mode 100644
index 0000000..5122af0
--- /dev/null
+++ b/brainfuck.erl
@@ -0,0 +1,143 @@
+% A Brainfuck Interpreter in Erlang
+%
+% Copyright (c) 2015, Jens Luedicke <jens.luedicke@gmail.com>
+% All rights reserved.
+%
+% Redistribution and use in source and binary forms, with or without
+% modification, are permitted provided that the following conditions are met:
+%     * Redistributions of source code must retain the above copyright
+%       notice, this list of conditions and the following disclaimer.
+%     * Redistributions in binary form must reproduce the above copyright
+%       notice, this list of conditions and the following disclaimer in the
+%       documentation and/or other materials provided with the distribution.
+%     * Neither the name of the <organization> nor the
+%       names of its contributors may be used to endorse or promote products
+%       derived from this software without specific prior written permission.
+%
+% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+% ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+% WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+% DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+% DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+% (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+% ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+% (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+% SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+-module(brainfuck).
+-export([run/1]).
+
+parse(Data) ->
+    case Data of
+        "+" -> opplus;
+        "-" -> opminus;
+        ">" -> opnext;
+        "<" -> opprev;
+        "," -> opin;
+        "." -> opout;
+        "[" -> oploopbegin;
+        "]" -> oploopend;
+        _   -> opignore
+    end.
+
+findloop([], LoopCodes, _) ->
+    LoopCodes;
+
+findloop([Op|OpCodes], LoopCodes, LoopDepth) ->
+%    io:format("findloop ~B ~n", [LoopDepth]),
+    if
+        (Op == oploopbegin) ->
+            findloop(OpCodes, lists:flatten([LoopCodes] ++ [Op]), LoopDepth + 1);
+        (Op == oploopend) and (LoopDepth > 1) ->
+            findloop(OpCodes, lists:flatten([LoopCodes] ++ [Op]), LoopDepth - 1);
+        (Op /= oploopbegin) and (Op /= oploopend) ->
+            findloop(OpCodes, lists:flatten([LoopCodes] ++ [Op]), LoopDepth);
+        (LoopDepth == 0) ->
+            LoopCodes;
+        true ->
+            LoopCodes
+    end.
+
+evalloop(OpCodes, Tape, Pos) ->
+    Value = maps:get(Pos, Tape, 0),
+%    io:format("evalloop ~B ~B ~n", [Pos, Value]),
+
+    if
+        Value /= 0 ->
+            {NewTape, NewPos} = eval(OpCodes, Tape, Pos),
+            evalloop(OpCodes, NewTape, NewPos);
+        true ->
+%            io:format("evalloop ~B ~B is 0. Stop.~n", [Pos, Value]),
+            {Tape, Pos}
+    end.
+
+eval([], Tape, Pos) -> {Tape, Pos};
+
+eval([Op|OpCodes], Tape, Pos) ->
+    case Op of
+        opplus ->
+            Value   = maps:get(Pos, Tape, 0) + 1,
+            NewTape = maps:put(Pos, Value, Tape),
+%            io:format("eval: opplus ~B ~B ~n", [Pos, Value]),
+            eval(OpCodes, NewTape, Pos);
+        opminus ->
+            Value   = maps:get(Pos, Tape, 0) - 1,
+            NewTape = maps:put(Pos, Value, Tape),
+%            io:format("eval: opminus ~B ~B ~n", [Pos, Value]),
+            eval(OpCodes, NewTape, Pos);
+        opnext ->
+%            io:format("eval: opnext ~B ~B ~n", [Pos, Pos + 1]),
+            eval(OpCodes, Tape, Pos + 1);
+        opprev ->
+%            io:format("eval: opprev ~B ~B ~n", [Pos, Pos - 1]),
+            eval(OpCodes, Tape, Pos - 1);
+        opin ->
+            Data = io:get_chars("", 1),
+            Char = lists:nth(1, Data),
+            io:format("eval: opin ~B ~B ~n", [Pos, Char]),
+            NewTape = maps:put(Pos, Char, Tape),
+            eval(OpCodes, NewTape, Pos);
+        opout ->
+            Value   = maps:get(Pos, Tape, 0),
+%            io:format("eval: opout ~B ~B ~n", [Pos, Value]),
+            io:format("~c", [Value]),
+            eval(OpCodes, Tape, Pos);
+        oploopbegin ->
+%            io:format("eval: oploopbegin ~B ~n", [Pos]),
+            LoopCodes = findloop(OpCodes, [], 1),
+            {NewTape, NewPos} = evalloop(LoopCodes, Tape, Pos),
+            eval(OpCodes -- LoopCodes, NewTape, NewPos);
+        oploopend ->
+%            io:format("eval: oploopend ~B ~n", [Pos]),
+            eval(OpCodes, Tape, Pos);
+        _ ->
+          eval(OpCodes, Tape, Pos)
+    end.
+
+read_file(IoDevice, OpCodes) ->
+    case file:read(IoDevice, 1) of
+        {ok, Data} ->
+            OpCode = parse(Data),
+            read_file(IoDevice, lists:flatten([OpCodes] ++ [OpCode]));
+        eof ->
+            {ok, OpCodes};
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+run(File) ->
+    case file:open(File, read) of
+        {ok, IoDevice} ->
+            case read_file(IoDevice, []) of
+                {ok, OpCodes} ->
+                    Tape = maps:new(),
+                    Pos = 0,
+                    eval(OpCodes, Tape, Pos);
+                {error, Reason} ->
+                    io:format("Unable to read file ~s: ~s ~n", [File, Reason])
+            end,
+            file:close(IoDevice);
+        {error, Reason} ->
+            io:format("Unable to open file ~s: ~s ~n", [File, Reason])
+    end.
diff --git a/hello.bf b/hello.bf
new file mode 100644
index 0000000..0f8b7da
--- /dev/null
+++ b/hello.bf
@@ -0,0 +1,2 @@
+>++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>]<<]>.+++++++..+++.>
+>+++++++.<<<[[-]<[-]>]<+++++++++++++++.>>.+++.------.--------.>>+.>++++.