diff -r 75d9f9e5906f -r 05cfce0fdef7 progs/comb1a.scala
--- a/progs/comb1a.scala	Thu Nov 07 00:07:16 2019 +0000
+++ b/progs/comb1a.scala	Thu Nov 14 01:21:02 2019 +0000
@@ -66,18 +66,18 @@
 implicit def char2parser(c: Char) = CharParser(c)
 
 implicit def ParserOps[I : IsSeq, T](p: Parser[I, T]) = new {
-  def || (q : => Parser[I, T]) = new AltParser[I, T](p, q)
+  def ||(q : => Parser[I, T]) = new AltParser[I, T](p, q)
   def ==>[S] (f: => T => S) = new FunParser[I, T, S](p, f)
   def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q)
 }
 
 implicit def StringOps(s: String) = new {
-  def || (q : => Parser[String, String]) = new AltParser[String, String](s, q)
-  def || (r: String) = new AltParser[String, String](s, r)
+  def ||(q : => Parser[String, String]) = new AltParser[String, String](s, q)
+  def ||(r: String) = new AltParser[String, String](s, r)
   def ==>[S] (f: => String => S) = new FunParser[String, String, S](s, f)
-  def ~[S] (q : => Parser[String, S]) = 
+  def ~[S](q : => Parser[String, S]) = 
     new SeqParser[String, String, S](s, q)
-  def ~ (r: String) = 
+  def ~(r: String) = 
     new SeqParser[String, String, String](s, r)
 }
 
@@ -106,20 +106,20 @@
 // Arithmetic Expressions (Terms and Factors)
 
 lazy val E: Parser[String, Int] = 
-  (T ~ "+" ~ E) ==> { case x ~ y ~ z => x + z } ||
-  (T ~ "-" ~ E) ==> { case x ~ y ~ z => x - z } || T 
+  (T ~ "+" ~ E) ==> { case x ~ _ ~ z => x + z } ||
+  (T ~ "-" ~ E) ==> { case x ~ _ ~ z => x - z } || T 
 lazy val T: Parser[String, Int] = 
-  (F ~ "*" ~ T) ==> { case x ~ y ~ z => x * z } || F
+  (F ~ "*" ~ T) ==> { case x ~ _ ~ z => x * z } || F
 lazy val F: Parser[String, Int] = 
-  ("(" ~ E ~ ")") ==> { case x ~ y ~ z => y } || NumParserInt
+  ("(" ~ E ~ ")") ==> { case _ ~ y ~ _ => y } || NumParserInt
 
 /* same parser but producing a string
 lazy val E: Parser[String, String] = 
-  (T ~ "+" ~ E) ==> { case ((x, y), z) => "(" + x + ")+(" + z + ")"} || T 
+  (T ~ "+" ~ E) ==> { case x ~ y ~ z => "(" + x + ")+(" + z + ")"} || T 
 lazy val T: Parser[String, String] = 
-  (F ~ "*" ~ T) ==> { case ((x, y), z) => "(" + x + ")*("+ z + ")"} || F
+  (F ~ "*" ~ T) ==> { case x ~ y ~ z => "(" + x + ")*("+ z + ")"} || F
 lazy val F: Parser[String, String] = 
-  ("(" ~ E ~ ")") ==> { case ((x, y), z) => y } || NumParser
+  ("(" ~ E ~ ")") ==> { case x ~ y ~ z => y } || NumParser
 */
 
 println(E.parse_all("1+3+4"))
@@ -191,7 +191,7 @@
 
 
 // a problem with the arithmetic expression parser -> gets 
-// slow with deep nestedness
+// slow with deeply nested parentheses
 println("Runtime problem")
 E.parse("1")
 E.parse("(1)")