x = 5 * 3;
   y = x + 2;

   Program    ::= { Definition }
   Definition ::= { IDENT "=" Expression ";" }
   Expression ::= Term { ("+"|"-") Term }
   Term       ::= Factor { ("*"|"/") Factor }
   Factor     ::= IDENT | INTLIT | "(" Expression ")"

The abstract syntax is

   Program    = PROGRAM { Definition }
   Definition = DEF String Expression
   Expression = IDENT String
              | INTLIT int
              | BINOP Expression Expression char

Your job is to complete the analyze-visitor in Analyzer.java and then to complete the interpreter visitor for names.

• Get the file exercice3.tar (Alternatively, if you have done the previous exercise, you can continue on that code).
• Unpack it with the command tar xof exercice3.tar (This will create a new directory exercice3).
• Go into the directory exercice3.
• Run make to compile the given sources
• Check the given analyzer with make analyzerTest < examples/example1.expr.
• Now complete the source of the analyzer in source/expression/Analyzer.java by writing the methods caseDef(..) and caseIdent(..).
• The tree data structure is given in source/expression/Tree.java
• Use Report.error(...) to give error messages.
• Recompile your analyzer with make and check it with make analyzerTest < examples/example1.expr
• Create your own examples, to see whether undefined/doubly defined identifiers are reported as errors correctly.
• Now complete the interpreter in source/expression/Interpreter.java by writing the methods caseDef(..) and caseIdent(..).
• The class Symbol has a field val, which you can use to store the value for the expression.
• Recompile your interpreter with make and check it with make interpreterTest < examples/example1.expr

• Modify the pretty-printer to emit valid Java-Code (a class Main) by modifying source/expression/Printer.java
• Use make printerTest < examples/example1.expr > Main.java to print the result into the file Main.java
• Compile with javac Main.java and run it with java Main.
• Does it work if you use Java keywords as identifiers?