***
***	RTA 2003 Maude 2.1 Demo:
***	Polymorphic list.
***

fmod POLY-LIST is
  sort List .
  op nil : -> List [ctor] .
  op __ : Universal List -> List [ctor poly (1)] .
endfm

fmod POLY-LIST-TEST is
  pr POLY-LIST + CONVERSION + QID .
  op list2string : List -> String .

  var L : List .
  var S : String . var Q : Qid .
  var R : Rat . var F : Float . 

  eq list2string(nil) = "" .
  eq list2string(S L) = S + list2string(L) .
  eq list2string(Q L) = "'" + string(Q) + list2string(L) .
  eq list2string(R L) = string(R, 10) + list2string(L) .
  eq list2string(F L) = string(F) + list2string(L) .
endfm

red list2string("The answer is " 42.0 " but that is only "
1/2 " of the " 'problem "." nil) .