--- a/while1.scala	Fri Nov 23 21:21:27 2012 +0000
+++ b/while1.scala	Sat Nov 24 07:08:51 2012 +0000
@@ -8,7 +8,7 @@
 val DIGIT = RANGE("0123456789")
 val ID = SEQ(SYM, STAR(ALT(SYM, DIGIT))) 
 val NUM = PLUS(DIGIT)
-val KEYWORD = ALTS("skip", "while", "do", "if", "then", "else", "true", "false", "print") 
+val KEYWORD = ALTS("skip", "while", "do", "if", "then", "else", "true", "false", "write") 
 val SEMI: Rexp = ";"
 val OP: Rexp = ALTS(":=", "=", "-", "+", "*", "!", "<", ">")
 val WHITESPACE = PLUS(RANGE(" \n"))
@@ -57,7 +57,7 @@
 case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt
 case class While(b: BExp, bl: Block) extends Stmt
 case class Assign(s: String, a: AExp) extends Stmt
-case class Print(s: String) extends Stmt
+case class Write(s: String) extends Stmt
 
 case class Var(s: String) extends AExp
 case class Num(i: Int) extends AExp
@@ -104,12 +104,13 @@
 
 // boolean expressions
 lazy val BExp: Parser[List[Token], BExp] = 
+  (T_KWD("true") ==> ((_) => True: BExp)) || 
+  (T_KWD("false") ==> ((_) => False: BExp)) ||
+  (T_LPAREN ~> BExp <~ T_RPAREN) ||
   (AExp ~ T_OP("=") ~ AExp) ==> { case ((x, y), z) => Bop("=", x, z): BExp } || 
   (AExp ~ T_OP("!=") ~ AExp) ==> { case ((x, y), z) => Bop("!=", x, z): BExp } || 
   (AExp ~ T_OP("<") ~ AExp) ==> { case ((x, y), z) => Bop("<", x, z): BExp } || 
-  (AExp ~ T_OP(">") ~ AExp) ==> { case ((x, y), z) => Bop(">", x, z): BExp } || 
-  (T_KWD("true") ==> ((_) => True)) || 
-  (T_KWD("false") ==> ((_) => False: BExp))
+  (AExp ~ T_OP(">") ~ AExp) ==> { case ((x, y), z) => Bop("<", z, x): BExp }
 
 lazy val Stmt: Parser[List[Token], Stmt] =
   (T_KWD("skip") ==> ((_) => Skip: Stmt)) ||
@@ -117,7 +118,7 @@
   (T_KWD("if") ~ BExp ~ T_KWD("then") ~ Block ~ T_KWD("else") ~ Block) ==>
     { case (((((x,y),z),u),v),w) => If(y, u, w): Stmt } ||
   (T_KWD("while") ~ BExp ~ T_KWD("do") ~ Block) ==> { case (((x, y), z), w) => While(y, w) } || 
-  (T_KWD("print") ~ IdParser) ==> { case (x, y) => Print(y) } 
+  (T_KWD("write") ~ IdParser) ==> { case (x, y) => Write(y) } 
 
 lazy val Stmts: Parser[List[Token], Block] =
   (Stmt ~ T_SEMI ~ Stmts) ==> { case ((x, y), z) => x :: z : Block } ||
@@ -135,8 +136,9 @@
   case False => false
   case Bop("=", a1, a2) => eval_aexp(a1, env) == eval_aexp(a2, env)
   case Bop("!=", a1, a2) => !(eval_aexp(a1, env) == eval_aexp(a2, env))
-  case Bop(">", a1, a2) => eval_aexp(a1, env) > eval_aexp(a2, env)
   case Bop("<", a1, a2) => eval_aexp(a1, env) < eval_aexp(a2, env)
+  case Bop("&&", a1, a2) => eval_aexp(a1, env) > eval_aexp(a2, env)
+  case Bop("||", a1, a2) => eval_aexp(a1, env) < eval_aexp(a2, env)
 }
 
 def eval_aexp(a: AExp, env : Env) : Int = a match {
@@ -154,7 +156,7 @@
   case While(b, bl) => 
     if (eval_bexp(b, env)) eval_stmt(While(b, bl), eval_bl(bl, env))
     else env
-  case Print(x) => { println(env(x)); env }
+  case Write(x) => { println(env(x)); env }
 }
 
 def eval_bl(bl: Block, env: Env) : Env = bl match {
@@ -164,11 +166,21 @@
 
 def eval_prog(name: String) : Env = {
   val tks = Tok.fromFile(name)
-  val ast = Stmts.parse_all(tks).head
+  val ast = Stmts.parse_single(tks)
   eval_bl(ast, Map.empty)
 }
 
 
 //examples
 
-eval_prog("fib.while")
+eval_prog("loops.while")
+//eval_prog("fib.while")
+
+
+
+
+
+
+
+
+