--- a/progs/comb2.scala	Wed Nov 06 23:27:19 2019 +0000
+++ b/progs/comb2.scala	Thu Nov 07 00:07:16 2019 +0000
@@ -103,13 +103,13 @@
 }
 
 lazy val AExp: Parser[String, AExp] = 
-  (Te ~ "+" ~ AExp) ==> { case x ~ y ~ z => Aop("+", x, z): AExp } ||
-  (Te ~ "-" ~ AExp) ==> { case x ~ y ~ z => Aop("-", x, z): AExp } || Te 
+  (Te ~ "+" ~ AExp) ==> { case x ~ _ ~ z => Aop("+", x, z): AExp } ||
+  (Te ~ "-" ~ AExp) ==> { case x ~ _ ~ z => Aop("-", x, z): AExp } || Te 
 lazy val Te: Parser[String, AExp] = 
-  (Fa ~ "*" ~ Te) ==> { case x ~ y ~ z => Aop("*", x, z): AExp } || 
-  (Fa ~ "/" ~ Te) ==> { case x ~ y ~ z => Aop("/", x, z): AExp } || Fa  
+  (Fa ~ "*" ~ Te) ==> { case x ~ _ ~ z => Aop("*", x, z): AExp } || 
+  (Fa ~ "/" ~ Te) ==> { case x ~ _ ~ z => Aop("/", x, z): AExp } || Fa  
 lazy val Fa: Parser[String, AExp] = 
-   ("(" ~ AExp ~ ")") ==> { case x ~ y ~ z => y } || 
+   ("(" ~ AExp ~ ")") ==> { case _ ~ y ~ _ => y } || 
    IdParser ==> Var || 
    NumParser ==> Num
 
@@ -119,8 +119,8 @@
    (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 } ||
+   ("(" ~ BExp ~ ")" ~ "&&" ~ BExp) ==> { case _ ~ y ~ _ ~ _ ~ v => And(y, v): BExp } ||
+   ("(" ~ BExp ~ ")" ~ "||" ~ BExp) ==> { case _ ~ y ~ _ ~ _ ~ v => Or(y, v): BExp } ||
    ("true" ==> (_ => True: BExp )) || 
    ("false" ==> (_ => False: BExp )) ||
    ("(" ~ BExp ~ ")") ==> { case _ ~ x ~ _ => x }
@@ -128,14 +128,14 @@
 // statement / statements
 lazy val Stmt: Parser[String, Stmt] =
   (("skip" ==> (_ => Skip: Stmt)) ||
-   (IdParser ~ ":=" ~ AExp) ==> { case x ~ y ~ z => Assign(x, z): Stmt } ||
-   ("write(" ~ IdParser ~ ")") ==> { case x ~y ~ z => Write(y): Stmt } ||
+   (IdParser ~ ":=" ~ AExp) ==> { case x ~ _ ~ z => Assign(x, z): Stmt } ||
+   ("write(" ~ IdParser ~ ")") ==> { case _ ~ y ~ _ => Write(y): Stmt } ||
    ("if" ~ BExp ~ "then" ~ Block ~ "else" ~ Block) ==>
-    { case x ~ y ~ z ~ u ~ v ~ w => If(y, u, w): Stmt } ||
-   ("while" ~ BExp ~ "do" ~ Block) ==> { case x ~ y ~ z ~ w => While(y, w) }) 
+    { case _ ~ y ~ _ ~ u ~ _ ~ w => If(y, u, w): Stmt } ||
+   ("while" ~ BExp ~ "do" ~ Block) ==> { case _ ~ y ~ _ ~ w => While(y, w) }) 
  
 lazy val Stmts: Parser[String, Block] =
-  (Stmt ~ ";" ~ Stmts) ==> { case x ~ y ~ z => x :: z : Block } ||
+  (Stmt ~ ";" ~ Stmts) ==> { case x ~ _ ~ z => x :: z : Block } ||
   (Stmt ==> ( s => List(s) : Block))
 
 // blocks (enclosed in curly braces)