Execute a Markov algorithm

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Execute a Markov algorithm
You are encouraged to solve this task according to the task description, using any language you may know.

Create an interpreter for a Markov Algorithm. Rules have the syntax:

<comment> ::= # {<any character>}
<rule> ::= <pattern> <whitespace> -> <whitespace> [.] <replacement>
<whitespace> ::= (<tab> | <space>) [<whitespace>]

There is one rule per line. If there is a . present before the <replacement>, then this is a terminating rule in which case the interpreter must halt execution.

Ruby

Works with: Ruby version 1.8.7

<lang Ruby>raise "Please input an input code file, an input data file, and an output file." if ARGV.size < 3

rules = File.readlines(ARGV[0]).inject([]) do |rules, line|

 if line =~ /^\s*#/
   rules
 elsif line =~ /^(.+)\s+->\s+(\.?)(.*)$/
   rules << [$1, $3, $2 != ""]
 else
   raise "Syntax error: #{line}"
 end

end

File.open(ARGV[2], "w") do |file|

 file.write(File.read(ARGV[1]).tap { |input_data|
   while (matched = rules.find { |match, replace, term|
     input_data[match] and input_data.sub!(match, replace)
   }) and !matched[2]
   end
 })

end</lang>