diff -r f63ba92a7d78 -r 774007c4b1b3 regexp.scala
--- a/regexp.scala	Wed Oct 10 14:08:49 2012 +0100
+++ b/regexp.scala	Thu Oct 11 10:58:18 2012 +0100
@@ -9,9 +9,13 @@
 case class STAR(r: Rexp) extends Rexp
 
 // some convenience for typing in regular expressions
-implicit def string2rexp(s : String) : Rexp = {
-  s.foldRight (EMPTY: Rexp) ( (c, r) => SEQ(CHAR(c), r) )
+def charlist2rexp(s : List[Char]) : Rexp = s match {
+  case Nil => EMPTY
+  case c::Nil => CHAR(c)
+  case c::s => SEQ(CHAR(c), charlist2rexp(s))
 }
+implicit def string2rexp(s : String) : Rexp = charlist2rexp(s.toList)
+
 
 // for example
 println(STAR("abc"))
@@ -99,3 +103,4 @@
 println(matcher("cab" ,"cab"))
 println(matcher(STAR("a"),"aaa"))
 
+