An example of a non-trivial core.logic predicate.

fix_adjunctiono.clj

(defn ^::rule fix-adjunctiono
  "A rule which takes a left-most or right-most child A, which is an
  adjunct, and puts the A on a separate level from the other children,
  i.e. (R A ...) -> (R A (R ...)) or (R ... A) -> (R (R ...) A).

  This solves the general case when modifiers and adjuncts end up as
  children of the consituent they modify (e.g. in VPs)."
  [in-tree out-tree]
  (fresh [root children other-children adjunct head-child]
    (conso root children in-tree)
    (has-more-thano 2 children)
    (conde [(conso adjunct other-children children)
            (== out-tree (list root adjunct head-child))]
           [(appendo other-children (list adjunct) children)
            (== out-tree (list root head-child adjunct))])
    (conso root other-children head-child)
    (adjuncto in-tree adjunct)))