adding tree support and printing

src/main/scala/leon/purescala/PrettyPrinter.scala

@@ -81,7 +81,12 @@ object PrettyPrinter {
     case IntLiteral(v) => sb.append(v)
     case BooleanLiteral(v) => sb.append(v)
     case StringLiteral(s) => sb.append("\"" + s + "\"")
-
+    case Tuple(exprs) => ppNary(sb, exprs, "(", ", ", ")", lvl)
+    case TupleSelect(t, i) => {
+      pp(t, sb, lvl)
+      sb.append("._" + i)
+      sb
+    }
     case OptionSome(a) => {
       var nsb = sb
       nsb.append("Some(")
@@ -297,6 +302,7 @@ object PrettyPrinter {
       nsb.append(" => ")
       pp(tt, nsb, lvl)
     }
+    case TupleType(tpes) => ppNaryType(sb, tpes, "(", ", ", ")", lvl)
     case c: ClassType => sb.append(c.classDef.id)
     case _ => sb.append("Type?")
   }

src/main/scala/leon/purescala/Trees.scala

@@ -37,6 +37,7 @@ object Trees {
   case class IfExpr(cond: Expr, then: Expr, elze: Expr) extends Expr 
 
   case class Tuple(exprs: Seq[Expr]) extends Expr
+  case class TupleSelect(tuple: Expr, index: Int) extends Expr
 
   object MatchExpr {
     def apply(scrutinee: Expr, cases: Seq[MatchCase]) : MatchExpr = {
@@ -359,6 +360,7 @@ object Trees {
       case SetMax(s) => Some((s,SetMax))
       case CaseClassSelector(cd, e, sel) => Some((e, CaseClassSelector(cd, _, sel)))
       case CaseClassInstanceOf(cd, e) => Some((e, CaseClassInstanceOf(cd, _)))
+      case TupleSelect(t, i) => Some((t, TupleSelect(_, i)))
       case _ => None
     }
   }
@@ -410,6 +412,7 @@ object Trees {
       case FiniteMap(args) => Some((args, (as : Seq[Expr]) => FiniteMap(as.asInstanceOf[Seq[SingletonMap]])))
       case FiniteMultiset(args) => Some((args, FiniteMultiset))
       case Distinct(args) => Some((args, Distinct))
+      case Tuple(args) => Some((args, Tuple))
       case _ => None
     }
   }