📝Datomic syntax

tags

Datomic

  • basic query structure

    • s

      [:find ...
 :in ...
 :where ...]
  • input parameters

    • s

      [:find ...
 :in $ % ?scalar
         [?descructuring1 ?descructuring2]
         [?each ...] ;; ... is not omission
         [[?rel-from ?rel-to]]
 :where ...]
  • where
    • [?e :attr ?v] simple match
    • [?e :attr ?v ?tx] match transaction (fourth element)
    • [(< ?v1 ?v2)] predicate
    • [(func ?v1) ?res] transformation. func can be any clojure or host function (e.g., Java one)
    • (rule ?v1 ?v2) rule invocation. note missing square brackets
  • rules
    • rules are passed in as % argument
    • % is an array of rules, where each rule has the following form

      • _

        [(name ?param1 ?param2) ;; rule head
 [?param1 :attr ?param2] ;; rule body
 ]
    • the body of the rule can use all the same form as [where | from Datalog]
    • if there are multiple rules with the same name, they act as OR. they will be tried in order

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