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EvalEx is a handy expression evaluator for Java, that allows to evaluate expressions.

There is a newer version: 3.4.0

/*
  Copyright 2012-2022 Udo Klimaschewski

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
*/
package com.ezylang.evalex.config;

import com.ezylang.evalex.operators.OperatorIfc;

/**
 * An operator dictionary holds all the operators, that can be used in an expression. 

 * The default implementation is the {@link MapBasedOperatorDictionary}.
 */
public interface OperatorDictionaryIfc {

  /**
   * Allows to add an operator to the dictionary. Implementation is optional, if you have a fixed
   * set of operators, this method can throw an exception.
   *
   * @param operatorString The operator name.
   * @param operator The operator implementation.
   */
  void addOperator(String operatorString, OperatorIfc operator);

  /**
   * Check if the dictionary has a prefix operator with that name.
   *
   * @param operatorString The operator name to look for.
   * @return true if an operator was found or false if not.
   */
  default boolean hasPrefixOperator(String operatorString) {
    return getPrefixOperator(operatorString) != null;
  }

  /**
   * Check if the dictionary has a postfix operator with that name.
   *
   * @param operatorString The operator name to look for.
   * @return true if an operator was found or false if not.
   */
  default boolean hasPostfixOperator(String operatorString) {
    return getPostfixOperator(operatorString) != null;
  }

  /**
   * Check if the dictionary has an infix operator with that name.
   *
   * @param operatorString The operator name to look for.
   * @return true if an operator was found or false if not.
   */
  default boolean hasInfixOperator(String operatorString) {
    return getInfixOperator(operatorString) != null;
  }

  /**
   * Get the operator definition for a prefix operator name.
   *
   * @param operatorString The name of the operator.
   * @return The operator definition or null if no operator was found.
   */
  OperatorIfc getPrefixOperator(String operatorString);

  /**
   * Get the operator definition for a postfix operator name.
   *
   * @param operatorString The name of the operator.
   * @return The operator definition or null if no operator was found.
   */
  OperatorIfc getPostfixOperator(String operatorString);

  /**
   * Get the operator definition for an infix operator name.
   *
   * @param operatorString The name of the operator.
   * @return The operator definition or null if no operator was found.
   */
  OperatorIfc getInfixOperator(String operatorString);
}