diff -r 29fc780ca130 -r fa7f7144f2bb main_templates3/re.scala
--- a/main_templates3/re.scala	Tue Dec 07 01:35:00 2021 +0000
+++ b/main_templates3/re.scala	Tue Dec 07 23:17:51 2021 +0000
@@ -12,6 +12,21 @@
 case class SEQ(r1: Rexp, r2: Rexp) extends Rexp   // sequence
 case class STAR(r: Rexp) extends Rexp             // star
 
+import scala.language.implicitConversions    
+import scala.language.reflectiveCalls 
+
+def charlist2rexp(s: List[Char]): Rexp = s match {
+  case Nil => ONE
+  case c::Nil => CHAR(c)
+  case c::s => SEQ(CHAR(c), charlist2rexp(s))
+}
+implicit def string2rexp(s: String): Rexp = charlist2rexp(s.toList)
+
+
+// "a|b"
+ALT(CHAR('a'), CHAR('b'))
+
+val reg : Rexp = "a" | "b" // CHAR('a')
 
 // some convenience for typing regular expressions
 
@@ -29,6 +44,9 @@
 }
 implicit def string2rexp(s: String): Rexp = charlist2rexp(s.toList)
 
+
+
+
 implicit def RexpOps (r: Rexp) = new {
   def | (s: Rexp) = ALT(r, s)
   def % = STAR(r)