MIDTERM               COM 1205                   Winter 2003
Tuesday, February 11

Question 1:
===========

Consider the following program.cd, program.beh and program.input
file and the output. Find the UNKNOWNS.


program.cd:
===============================================================

import edu.neu.ccs.demeter.dj.*;

Main = <s> String.

Aspect = "aspect" 
  <an> TraversalAspectName 
  <sts> SList(Decl).
Decl = "declare" Item.
Item : NamedStrat | Trav.
NamedStrat = "strategy" ":" StrategyName ":" Strat.
Trav = "traversal" ":" 
  MethodSignature ":" StrategyName "(" ClassName ")".
MethodSignature = "void" MethodName "(" FormalArgument ")".
FormalArgument = ClassName VariableName.

TraversalAspectName = Ident.
StrategyName = Ident.
ClassName = Ident.
MethodName = Ident.
Strat = String.
VariableName = Ident.

SList(S) ~ "{" S {";" S } "}".

program.beh:
===============================================================

Main {
  {{
  static ClassGraph cg;
  public static void main(String args[]) throws Exception {
    Aspect m = Aspect.parse(System.in);
    System.out.println("input ===================== ");
    m.display();
    System.out.println();
    System.out.println(" processing starts ");
    cg = new ClassGraph(true, false);
    cg.traverse(m,
      "from Aspect to ClassName", new Visitor() {
    void before (ClassName host) {
      System.out.println(host.get_ident().toString());
    }
    });
    System.out.println("done: from Aspect to ClassName");

    cg.traverse(m,
      "from Aspect via MethodSignature to ClassName", new Visitor() {
    void before (ClassName host) {
      System.out.println(host.get_ident().toString());
    }
    });
    System.out.println("done: from Aspect via MethodSignature to ClassName");
  }
  }}
}

program.input:
===============================================================

// aspect {
//   void display() to * (DisplayVisitor);
// }

aspect Traversals {
  declare strategy: eachCommand: "from Commands to Command";
  declare traversal:
    void interpret(CompoundFile cd): eachCommand(Interpreter)
}

OUTPUT:
==============================================================


input ===================== 
: Aspect  (
  <an> : TraversalAspectName  (
    <ident>  : Ident "Traversals" )
  <sts> : Decl_SList  {
    <first> : Nonempty_Decl_SList  (
      <it> : Decl  (
        <item> : NamedStrat  (
	  <strategyname> : StrategyName  (
		<ident>  : Ident "eachCommand" )
	  <strat> : Strat  (
		<string>  : String "from Commands to Command"  ) ) )
     <next> : Nonempty_Decl_SList  (
      <it> : Decl  (
	<item> : Trav  (
		<methodsignature> : MethodSignature  (
			<methodname> : MethodName  (
				<ident>  : Ident "interpret" )
			<formalargument> : FormalArgument  (
				<classname> : ClassName  (
					<ident>  : Ident "CompoundFile" )
				<variablename> : VariableName  (
					<ident>  : Ident "cd" ) ) )
		<strategyname> : StrategyName  (
			<ident>  : Ident "eachCommand" )
		<classname> : ClassName  (
			<ident>  : Ident "Interpreter" ) ) ) ) ) } )
 processing starts 
CompoundFile
Interpreter
done: from Aspect to ClassName
CompoundFile
done: from Aspect via MethodSignature to ClassName

Question 2:
=========================================================================


The following lines from the above *.beh file
contain significant duplication.
Rewrite the program so that the duplication is minimized
and the behavior stays the same.

cg.traverse(m,
  "from Aspect to ClassName", new Visitor() {
    void before (ClassName host) {
      System.out.println(host.get_ident().toString());
    }
    });

cg.traverse(m,
  "from Aspect via MethodSignature to ClassName", new Visitor() {
    void before (ClassName host) {
      System.out.println(host.get_ident().toString());
    }
    });


Question 3:
==========================================================================


Is the following a legal sentence? Explain.

aspect Traversals {
  declare strategy: eachCommand: "from Commands to Command";
   declare traversal:
       void listAll(): eachFile(FileLister);
   declare traversal:
       void listAll(X x, Y y): eachFile(FileLister);
}

If it is not illegal describe how you would change the
class dictionary.