Interpreter

Thursday, 20 January 2005 21:36

Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.

Source code

/**
 * Declares an abstract Interpret operation that is common to all nodes in the
 * abstract syntax tree.
 * 
 * @role __InterpreterExpression
 */
public abstract class AbstractExpression {
        public abstract void interpret(Context context);}

/**
 * Builds an abstract syntax tree representing a particular sentence in the
 * language that the grammar defines. Invokes the Interpret operation.
 */
public class Client {
        public AbstractExpression getExpression() {
                // put your code to create expression here
                return null;        }

        public void sampleOperation() {
                Context context = new Context();                
                getExpression().interpret(context);        
        }

}

/**
 * Contains information that is global to interpreter.
 * 
 * @role __InterpreterContext
 */
public class Context {
}

/**
 * One such class is required for every rule in the grammar.
 */
public class NonterminalExpression extends AbstractExpression {
        public void interpret(Context context) {
                // put your code here
        }

}

/**
 * Implements an Interpret operation associated with terminal symbols in the
 * grammar.
 */
public class TerminalExpression extends AbstractExpression {
        public void interpret(Context context) {
                // put your code here
        }

}