Question

I am trying to write a configuration file for an erlang application (rabbitmq) whose conf si written as an erlang term 1.

My attribute is a ruby hash, do you know how I can convert this hash to a pretty printed erlang term ?

Answer 1

If I had to do this on my own, maybe something like:

def to_erl(o)
  case o
  when Hash
    '[' +
       o.map {|(k,v)|
        "{#{k}, #{to_erl v}}"
       }.join(",\n") +
     ']'
  when Array
    '[' + o.map{|v| to_erl(v)}.join(",")  +']'
  when TrueClass then "true"
  when FalseClass then "false"
  when Integer then o.to_s
  when String then o
  when Symbol then o.to_s
  # ... and whatever else you can think of
  else
    raise "Don't know how to erlify #{o}"
  end
end

… But I bet there’s some nice code you can steal off of some
open source project that has to serialize between ruby and erlang.

For serialization to erlang, BERT is the defacto (Binary Erlang terms).
There’s lots of libraries that go from Ruby hashes to BERT, it seems.
Haven’t seen one that gives you plain textual erlang terms.

Since this is for a chef recipe, it’s a good idea not to mess with
too many ruby dependencies at converge time. You’ll be calling #to_hash
on your chef attributes, and what you will get back will straight-forward
enough (no objects, just number/bools/strings/arrays and hashes I guess)
to manage with a bit of home grown code.