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