--- a/src/main/scala/RDB2RDFMain.scala	Wed Dec 16 19:19:15 2009 -0500
+++ b/src/main/scala/RDB2RDFMain.scala	Wed Dec 16 19:26:42 2009 -0500
@@ -13,7 +13,7 @@
 case class Enum(relaliasattr:RelAliasAttribute) extends Binding
 
 object RDB2RDF {
-  case class R2RState(allVars:List[Var], inConstraint:Set[Var], joins:Set[AliasedResource], varmap:Map[Var, SQL2RDFValueMapper], exprs:Set[PrimaryExpression])
+  case class R2RState(allVars:Set[Var], inConstraint:Set[Var], joins:Set[AliasedResource], varmap:Map[Var, SQL2RDFValueMapper], exprs:Set[PrimaryExpression])
 
   sealed abstract class SQL2RDFValueMapper(relaliasattr:RelAliasAttribute)
   case class StringMapper(relaliasattr:RelAliasAttribute) extends SQL2RDFValueMapper(relaliasattr)
@@ -164,7 +164,7 @@
 	      case OLit(l) => exprs += literalConstraint(objattr, l, dt)
 	      case OUri(u) => exprs += uriConstraint(objattr, u)
 	      case OVar(v) => {
-		allVars = allVars ::: List(v)
+		allVars += v
 		// !! 2nd+ ref implies constraint
 		val binding = varConstraint(objattr, v, db, rel)
 		varmap += v -> binding
@@ -240,7 +240,7 @@
 
     /* Create an object to hold our compilation state. */
     var r2rState = R2RState(
-      List[Var](), 
+      Set[Var](), 
       Set[Var](), 
       Set[AliasedResource](), 
       Map[Var, SQL2RDFValueMapper](), 
@@ -252,10 +252,10 @@
 
     /* Select the attributes corresponding to the variables
      * in the SPARQL SELECT.  */
-    var attrlist:List[NamedAttribute] = List()
-    attrs.attributelist.foreach(vvar => attrlist = attrlist ::: List(
+    var attrlist:Set[NamedAttribute] = Set()
+    attrs.attributelist.foreach(vvar => attrlist += 
       NamedAttribute(varToAttribute(r2rState.varmap, vvar), AttrAlias(Name("A_" + vvar.s)))
-    ))
+    )
 
     var exprs:Set[PrimaryExpression] = r2rState.exprs
     var inConstraint:Set[Var] = r2rState.inConstraint

--- a/src/main/scala/SQL.scala	Wed Dec 16 19:19:15 2009 -0500
+++ b/src/main/scala/SQL.scala	Wed Dec 16 19:26:42 2009 -0500
@@ -4,7 +4,7 @@
 import java.net.URI
 
 case class Select(attributelist:AttributeList, tablelist:TableList, expression:Expression)
-case class AttributeList(attributes:List[NamedAttribute])
+case class AttributeList(attributes:Set[NamedAttribute])
 case class NamedAttribute(fqattribute:RelAliasAttribute, attralias:AttrAlias)
 //case class RelAttribute(relation:Relation, attribute:Attribute) c.f. ForeignKey
 case class RelAliasAttribute(relalias:RelAlias, attribute:Attribute)
@@ -60,7 +60,7 @@
     "WHERE" ~ expression ^^ { case "WHERE" ~ expression => expression }
 
   def attributelist:Parser[AttributeList] =
-    repsep(namedattribute, ",") ^^ { AttributeList(_) }
+    repsep(namedattribute, ",") ^^ { l => AttributeList(l.toSet) }
 
   def namedattribute:Parser[NamedAttribute] =
     fqattribute ~ "AS" ~ attralias ^^

--- a/src/test/scala/SQLTest.scala	Wed Dec 16 19:19:15 2009 -0500
+++ b/src/test/scala/SQLTest.scala	Wed Dec 16 19:26:42 2009 -0500
@@ -13,7 +13,7 @@
             INNER JOIN Employee AS R_manager
  WHERE R_manager.id=R_emp.manager AND R_emp.lastName IS NOT NULL AND R_manager.lastName IS NOT NULL
 """
-    val expected = Select(AttributeList(List(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
+    val expected = Select(AttributeList(Set(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
 									      Attribute(Name("lastName"))),
 							    AttrAlias(Name("A_empName"))),
 					     NamedAttribute(RelAliasAttribute(RelAlias(Name("R_manager")),
@@ -36,7 +36,7 @@
   FROM Employee AS R_emp
  WHERE R_emp.manager=18 AND R_emp.lastName IS NOT NULL
 """
-    val expected = Select(AttributeList(List(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
+    val expected = Select(AttributeList(Set(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
 									      Attribute(Name("lastName"))),
 							    AttrAlias(Name("A_empName"))))),
 			  TableList(Set(AliasedResource(Relation(Name("Employee")),RelAlias(Name("R_emp"))))),
@@ -54,7 +54,7 @@
        INNER JOIN Employee AS R_manager
 WHERE R_emp.manager=R_manager.id AND R_manager.lastName="Johnson" AND R_emp.lastName IS NOT NULL
 """
-    val expected = Select(AttributeList(List(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
+    val expected = Select(AttributeList(Set(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")),
 									      Attribute(Name("lastName"))),
 							    AttrAlias(Name("A_empName"))))),
 			  TableList(Set(AliasedResource(Relation(Name("Employee")),RelAlias(Name("R_emp"))),
@@ -82,7 +82,7 @@
    AND R_grandManager.birthday < R_manager.birthday
    AND R_emp.lastName IS NOT NULL AND R_grandManager.lastName IS NOT NULL
 """
-    val expected = Select(AttributeList(List(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")), Attribute(Name("lastName"))),
+    val expected = Select(AttributeList(Set(NamedAttribute(RelAliasAttribute(RelAlias(Name("R_emp")), Attribute(Name("lastName"))),
 							    AttrAlias(Name("A_empName"))),
 					     NamedAttribute(RelAliasAttribute(RelAlias(Name("R_grandManager")),Attribute(Name("lastName"))),
 							    AttrAlias(Name("A_grandManagName"))))),