module util
imports libstrategolib

rules
  join(|infix) : [] -> ""
  join(|infix) : [x | xs] -> <conc-strings>(x, <prejoin(|infix)>xs)

  prejoin(|infix) : [] -> ""
  prejoin(|infix) : [x | xs] -> <concat-strings>[infix,x,<prejoin(|infix)>xs]