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[MATCH-95] recur detection logic is too naive Created: 16/Apr/14  Updated: 17/Apr/14

Status: Open
Project: core.match
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Major
Reporter: David Nolen Assignee: David Nolen
Resolution: Unresolved Votes: 0
Labels: None


 Description   

The following explodes because of the presence of recur:

(defn rec [expr]
  (match expr
         [:global] 'GLOBAL
         [:constant x] x
         [:variable x] x
         [:lazy-variable x] `(deref ~x)
         [:if test if-true if-false] `(if ~(rec test)
                                        ~(rec if-true)
                                        ~(rec if-false))
         [:delist list index] `(get ~(rec list) ~(rec index))
         [:depair pair key] `(get ~(rec pair) ~(match key :first 0 :second 1))
         [:list elements] (map rec elements)
         [:fold-recur index-arg list-sym] `(recur (+ 1 ~index-arg) (rest ~list-sym))
         [:zip left right] `(map vector ~(rec left) ~(rec right))
         [:filter list arg body] `(filter (fn [~arg] ~(rec body) ~(rec list)))
         [:len list] `(count ~(rec list))
         [:pair first second] [(rec first) (rec second)]
         [:block arg body] `(fn [~arg] ~(rec body))
         [:app f arg] `(~(rec f) ~(rec arg))
         [:query e annotations] `(QUERY ~(rec e) ~annotations)
         [:lookup key] `(LOOKUP ~key)
         [:let name value expr] `(let [~name ~value] expr)
         ; ... about 15 more
         ))


 Comments   
Comment by Jeanine Adkisson [ 17/Apr/14 1:52 PM ]

A hacky workaround is to interpolate the 'recur symbol from an outer scope.

(def recur-sym 'recur)

(match expr
  ... `(~recur-sym ...))
Comment by David Nolen [ 17/Apr/14 1:58 PM ]

Now that tools.analyzer exists it won't be difficult to solve this properly.





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