LogicalExpression.java

import java.util.*;

public class LogicalExpression {
	
	    private String uniqueSymbol = null; 	// null if sentence is a more complex expression
	    private String connective = null; 		// null if sentence is a _UNIQUE_ symbol
		private Vector<LogicalExpression> subexpressions = null;   // a vector of LogicalExpressions ( basically a vector of unique symbols and subexpressions )
		
		//constructor
		public LogicalExpression()
		{
			
			//these need to stay null if they're empty
			//this.uniqueSymbol = "0";
			//this.connective = "0";
			this.subexpressions = new Vector<LogicalExpression>();
		}
		
		// another constructor that will ( or is supposed to ) create
		// a new logical Expression, essentially making a copy
		public LogicalExpression( LogicalExpression oldExpression ) {
			
			if( oldExpression.getUniqueSymbol() == null) {
				this.uniqueSymbol = oldExpression.getUniqueSymbol();
			} else {
				// create a new logical expression from the one passed to it
				this.connective = oldExpression.getConnective();
			
				// now get all of the subExpressions
				// hint, enumerate over the subexpression vector of newExpression
				for( 
				Enumeration<LogicalExpression> e = oldExpression.getSubexpressions().elements(); e.hasMoreElements(); ) {
					LogicalExpression nextExpression = (LogicalExpression)e.nextElement();
					
					this.subexpressions.add( nextExpression );
				}
			}
			
		}
	
		/* this method replaces _part_ of read_word()
		 * this method sets the symbol for the LogicalExpression
		 * it checks to make sure that it starts with one of the appropriate letters,
		 * then checks to make sure that the rest of the string is either digits or '_'
		 */
		public void setUniqueSymbol( String newSymbol ) 
            {
			boolean valid = true;

			//remove the leading whitespace
			newSymbol.trim();
			
			if( this.uniqueSymbol != null ) 
                  {
			      System.out.println("setUniqueSymbol(): - this LE already has a unique symbol!!!" +
							"\nswapping :->" + this.uniqueSymbol + "<- for ->" + newSymbol +"<-\n");
			} 
                  else if( valid ) 
                  {
					this.uniqueSymbol = newSymbol;
					//testing
					//System.out.println(" setUniqueSymbol() - added-" + newSymbol + "- to the LogicalExpression! ");
			} 
		}

		/* this method replaces _part_ of read_word() from the example code 
		 * it sets the connective for this LogicalExpression
		 * 
		 * and returns the rest of the string to collect the symbols for it
		 */
		public String setConnective( String inputString ) {
			
			String connect;
			
			//testing
			//System.out.println("setConnective() - beginning -" + inputString + "-");
			
			// trim the whitespace at the beginning of the string if there is any
			// there shouldn't be
			inputString.trim();
			
			// if the first character of the inputString is a '('
			// - remove the ')' and the ')' and any whitespace after it.
			if( inputString.startsWith("(") ) {
				inputString = inputString.substring( inputString.indexOf('('), inputString.length() );
				
				//trim the whitespace
				inputString.trim();
			}
			
			//testing
			//System.out.println("here: setConnective1- inputString:" + inputString + "--");
			

			if( inputString.contains( " " ) ) {
				// remove the connective out of the string
				connect = inputString.substring( 0, inputString.indexOf( " " )) ;
				inputString = inputString.substring( ( connect.length() + 1 ), inputString.length() );
				//inputString.trim();
				
				//testing
				//System.out.println("I have the connective -" + connect + "- and i've got symbols -" + inputString + "-");
				
			} else {
				// just set to get checked and empty the inputString
				// huh?
				connect = inputString;
				inputString = "";
			}
			
			// if connect is a proper connective
			if ( connect.equalsIgnoreCase( "if" ) ||
					connect.equalsIgnoreCase( "iff" ) ||
					connect.equalsIgnoreCase( "and" ) ||
					connect.equalsIgnoreCase("or") ||
					connect.equalsIgnoreCase("xor") || 
					connect.equalsIgnoreCase( "not" ) ) {
				// ok, first word in the string is a valid connective

				// set the connective
				this.connective = connect;
				
				//testing
				//System.out.println( "setConnective(): I have just set the connective\n->" + connect + "<-\nand i'm returning\n->" + inputString + "<-" );
				
				return inputString;
				
			} else {
				System.out.println( "unexpected character!!! : invalid connective!! - setConnective():-" + inputString );
				LogicalExpression.exit_function( 0 );
			}
			
			// invalid connective - no clue who it would get here
			System.out.println(" invalid connective! : setConnective:-" + inputString );
			return inputString;
		}
		
		public void setSubexpression( LogicalExpression newSub ) {
			this.subexpressions.add(newSub);
		}
		
		public void setSubexpressions( Vector<LogicalExpression> symbols ) {
			this.subexpressions = symbols;
			
		}
		
		public String getUniqueSymbol(){
			return this.uniqueSymbol;
		}
		
		public String getConnective() {
			return this.connective;
		}
		
		public LogicalExpression getNextSubexpression() {
			return this.subexpressions.lastElement();
		}
		
		public Vector<LogicalExpression> getSubexpressions() {
			return this.subexpressions;
		}

	    private static void exit_function(int value) {
                System.out.println("exiting from LogicalExpression");
                  System.exit(value);
                }
	}