Sequence transformation by example
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Sequence transformations by example.

Inherits all capabilities of core.match, but extends this with the ability to build sequence transformers using elipsis notation.

I don't know how general this can be made to be but I'm naively experimenting with various ideas right now. I've just defined a basic macro that understands a simple elipsis and expands to a mapping. The (ambitious? easy?) goal is fully general declarative (and oh yeah, performant) compilation of sequence transformers defined using an intuitive elipsis notation.



Create a Transformer Function

(tr <pattern-in> <pattern-out>)

Define a Transformer Function

(deftr <function-name> <pattern-in> <pattern-out>)

Pattern Specification

The non-elipsis case is itself very powerful; that is the power of core.match / core.logic (at best I've added a thin layer of syntax around it).

(deftr some-thing->other-thing
  {:a [x] :b [y]}
  {x {:s y}})

(some-thing->other-thing {:a [:q] :b [2]})   =>  {:q {:s 2}}

Specifying a sequence transformation involves the ... symbol.

(deftr fooz->barz
  [{:a a :b c} ...]
  [[a c] ...])

(fooz->barz [{:a 1 :b 2} {:a 3 :b 4}])  =>  ([1 2] [3 4]))

Future Work / Next Steps

I'm not sure how easy or hard this will be, but if it is easy it will probably be because core.match has already done most of theoretical/applied magic for me. I would like to be able to use elipses notation in a more general way on all sorts of complex structures. For example, something like this should be possible:

(deftr raw-data->new-format
  {uuid [{_ _ :ts ts :value value}

  [{:uuid uuid
    :data [{:ts ts :value value}

   [{:uuid "123", :timestamp "1293883200000", :value "1.0"}
    {:uuid "123", :timestamp "1293884100000", :value "2.0"}
    {:uuid "123", :timestamp "1293969600000", :value "3.0"}
    {:uuid "123", :timestamp "1293970500000", :value "4.0"}],
   [{:uuid "321", :timestamp "1293883200000", :value "1.2"}
    {:uuid "321", :timestamp "1293884100000", :value "2.2"}
    {:uuid "321", :timestamp "1293969600000", :value "3.2"}
    {:uuid "321", :timestamp "1293970500000", :value "4.2"}]})


  [{:uuid "321",
    [{:timestamp "1293883200000", :value "1.2"}
     {:timestamp "1293884100000", :value "2.2"}
     {:timestamp "1293969600000", :value "3.2"}
     {:timestamp "1293970500000", :value "4.2"}]}
   {:uuid "123",
    [{:timestamp "1293883200000", :value "1.0"}
     {:timestamp "1293884100000", :value "2.0"}
     {:timestamp "1293969600000", :value "3.0"}
     {:timestamp "1293970500000", :value "4.0"}]}]


Copyright (C) 2012 Robert P. Levy

Distributed under the Eclipse Public License, the same as Clojure.