brainfuck.rb

raise "No file specified"    unless ARGV[0]
raise "File does not exist"  unless File.exists?(ARGV[0])
raise "File is not readable" unless File.readable?(ARGV[0])
file = File.open(ARGV[0])

cells    = Array.new(30000, 0)
min_size = 0
max_size = 255
location = 0

while not file.eof?
    char = file.getc
    case char
        when ?>
            location += 1 if location < cells.length
        when ?<
            location -= 1 if location > 0
        when ?+
            cells[location] += 1
            cells[location] = min_size if cells[location] > max_size
        when ?-
            cells[location] -= 1
            cells[location] = max_size if cells[location] < min_size
        when ?.
            $stdout.putc cells[location]
        when ?,
            cells[location] = $stdin.getc
        when ?[
            if cells[location] == 0
                nested = 1
                begin
                    _char = file.getc
                    nested += 1 if _char == ?[
                    nested -= 1 if _char == ?]
                end until nested == 0
            end
        when ?]
            if cells[location] != 0
                nested = 1
                begin
                    file.pos = file.pos - 2
                    _char = file.getc
                    nested += 1 if _char == ?]
                    nested -= 1 if _char == ?[
                end until nested == 0
            end
    end
end