Assignment 2: AspectJ

1
Assignment 2 AspectJ
2
The simple language

• Tiny program
• y2
• x2y3
• zxy2
• A program is a sequence of assignments
• Expressions on the right hand side of assignment
  statements are arithmetic expressions
• Assume variables are always of integer types
• Arithmatic operators include , -, , and /.
  There are no other operators.
• Assume input is always correct.

3
Parsing

• The parser creates an abstract syntax tree
  represented in Program class
• public class UseParser
• public static void main(String args)
• try
• File inputFile new File("calc.tiny")
• Calc2Parser parser new Calc2Parser(new
  Calc2Scanner(
• new FileReader(inputFile)))
• Program pm (Program) parser.parse().value
• System.out.println(pm.toString())
• catch (Exception e)
• e.printStackTrace()

4
Parsing result

•   lt?xml version"1.0" encoding"UTF-8" ?gt
• - ltprogramgt
• - ltassignmentgt
•   ltlhsgtzlt/lhsgt
• - ltrhsgt
• - ltexprgt
•   ltopgtlt/opgt
• - ltleftgt
• - ltexprgt
•   ltprimitivegtxlt/primitivegt
•   lt/exprgt
•   lt/leftgt

• - ltrightgt
• - ltexprgt
•   ltopgtlt/opgt
• - ltleftgt
• - ltexprgt
•   ltprimitivegtylt/primitivegt
•   lt/exprgt
•   lt/leftgt
• - ltrightgt
• - ltexprgt
•   ltprimitivegt2lt/primitivegt
•   lt/exprgt
•   lt/rightgt
•   lt/exprgt
•   lt/rightgt
•   lt/exprgt
•   lt/rhsgt
•   lt/assignmentgt

Program.java Assignment.java Expr.java
5
Program class consists of a vector of statements

• public class Program
• private Vector ltStatementgt statements
• public static HashtableltString, Exprgt
  varTablenew HashtableltString, Exprgt()
• public Program(Statement s)
• statements new Vector ltStatementgt()
• statements.add(s)
• public Program(Statement s, Program p)
• statements p.getStatements()
• statements.add(s)
• public String toString()

6
Assignment class

• public class Assignment extends Statement
• private String lhs private Expr rhs
• public Assignment(String l, Expr r)
• lhsl
• rhsr
• Program.varTable.put(l,r)
• public String getLHS() return lhs
• public Expr getRHS() return rhs

7
Your tasks

• Print out the parsed program
•          y 2         x (2y3)         
  z (x(y2))
• Hint Suppress printout in the parser by skipping
  calls to System.out.println(..) in UseParser
• Hint Define your own print method in classes
  such as Expr, Assignment.
• Print out the total number of expressions in this
  program
• Hint count calls to constructors
• Evaluate the program
•       ygt2
•       xgt8
•       zgt12
• Hint add evaluation method into Expr class
• Print indented trace of the evaluation process
• Hint check JoinPointTraceAspect in account
  example
• Count the nested level

8
Your output

• Assignment 2 is z(x(y2))
• (x(y2))gt ?
• xgt ?
• (2(23))gt ?
• 2gt ?
• 2gt2
• (23)gt ?
• 2gt ?
• 2gt2
• 3gt ?
• 3gt3
• (23)gt6
• (2(23))gt8
• 8gt8
• (y2)gt ?
• ygt ?
• 2gt ?
• 2gt2
• 2gt2

• Assignment 0 is y2
• 2gt ?
• 2gt2
• Assignment 1 is x(2(y3))
• (2(y3))gt ?
• 2gt ?
• 2gt2
• (y3)gt ?
• ygt ?
• 2gt ?
• 2gt2
• 2gt2
• 3gt ?
• 3gt3
• (23)gt6
• (2(23))gt8