/* This class defines Strings that denote the four basic arithmetic
** operators and has a method that returns the result of applying a
** given operator to two given integers.
**
** Author: R. McCloskey
** Date: Feb. 2022
*/

public class Operator {

   // class constants
   // ---------------
   public static final String PLUS = "+";
   public static final String MINUS = "-";
   public static final String TIMES = "*";
   public static final String DIVIDEDBY = "/";


   /* Returns the number resulting from applying the given operator to
   ** the given operands.
   */
   public static int apply(int left, String operator, int right) {
      if (operator.equals(PLUS)) { return left + right; }
      else if (operator.equals(MINUS)) { return left - right; }
      else if (operator.equals(TIMES)) { return left * right; }
      else if (operator.equals(DIVIDEDBY)) { return left / right; }
      else {
         String errorMessage = " is not a legal operator.";
         throw new IllegalArgumentException(operator + errorMessage);
      }
   }

   /* Reports whether the given string describes one of the operators
   ** supported by this class.
   */
   public static boolean isOperator(String str) {
      return str.equals(PLUS) ||
             str.equals(MINUS) ||
             str.equals(TIMES) ||
             str.equals(DIVIDEDBY);
   }

}