(.using
 [library
  [lux (.except Type)
   [abstract
    [equivalence (.only Equivalence)]
    [order (.only Order)]
    [hash (.only Hash)]]
   [data
    ["[0]" product]
    ["[0]" text ("[1]#[0]" order)
     ["%" format (.only format)]]]]]
 ["[0]" //
  ["[1]" artifact (.only Artifact) ("[1]#[0]" order)
   [type (.only Type)]]])

(type: .public Dependency
  (Record
   [#artifact Artifact
    #type Type]))

(def: .public hash
  (Hash Dependency)
  (all product.hash
       //.hash
       text.hash
       ))

(def: .public equivalence
  (Equivalence Dependency)
  (# hash equivalence))

(implementation: .public order
  (Order Dependency)

  (def: equivalence
    ..equivalence)

  (def: (< reference subject)
    (<| (or (//#< (the #artifact reference)
                  (the #artifact subject)))
        
        (and (//#= (the #artifact reference)
                   (the #artifact subject)))
        (text#< (the #type reference)
                (the #type subject)))))