diff -r c6c79d21f8a8 -r 1ee523c4f098 progs/comb2.scala
--- a/progs/comb2.scala	Wed Nov 06 23:17:05 2019 +0000
+++ b/progs/comb2.scala	Wed Nov 06 23:27:19 2019 +0000
@@ -115,10 +115,10 @@
 
 // boolean expressions with some simple nesting
 lazy val BExp: Parser[String, BExp] = 
-   (AExp ~ "==" ~ AExp) ==> { case x ~ y ~ z => Bop("==", x, z): BExp } || 
-   (AExp ~ "!=" ~ AExp) ==> { case x ~ y ~ z => Bop("!=", x, z): BExp } || 
-   (AExp ~ "<" ~ AExp) ==> { case x ~ y ~ z => Bop("<", x, z): BExp } || 
-   (AExp ~ ">" ~ AExp) ==> { case x ~ y ~ z => Bop(">", x, z): BExp } ||
+   (AExp ~ "==" ~ AExp) ==> { case x ~ _ ~ z => Bop("==", x, z): BExp } || 
+   (AExp ~ "!=" ~ AExp) ==> { case x ~ _ ~ z => Bop("!=", x, z): BExp } || 
+   (AExp ~ "<" ~ AExp) ==> { case x ~ _ ~ z => Bop("<", x, z): BExp } || 
+   (AExp ~ ">" ~ AExp) ==> { case x ~ _ ~ z => Bop(">", x, z): BExp } ||
    ("(" ~ BExp ~ ")" ~ "&&" ~ BExp) ==> { case x ~ y ~ z ~ u ~ v => And(y, v): BExp } ||
    ("(" ~ BExp ~ ")" ~ "||" ~ BExp) ==> { case x ~ y ~ z ~ u ~ v => Or(y, v): BExp } ||
    ("true" ==> (_ => True: BExp )) ||