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EvalEx is a handy expression evaluator for Java, that allows to evaluate simple mathematical and boolean expressions.
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/*
 * Copyright 2018 Udo Klimaschewski
 *
 * http://UdoJava.com/
 * http://about.me/udo.klimaschewski
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */
package com.udojava.evalex;

import com.udojava.evalex.Expression.ExpressionException;
import com.udojava.evalex.Expression.LazyNumber;
import java.math.BigDecimal;

/**
 * Abstract implementation of an unary operator.

 * 

 * This abstract implementation implements eval so that it forwards its first parameter to
 * evalUnary.
 */
public abstract class AbstractUnaryOperator extends AbstractOperator {


  /**
   * Creates a new operator.
   *
   * @param oper       The operator name (pattern).
   * @param precedence The operators precedence.
   * @param leftAssoc  true if the operator is left associative,
   *                   else false.
   */
  protected AbstractUnaryOperator(String oper, int precedence, boolean leftAssoc) {
    super(oper, precedence, leftAssoc);
  }


  @Override
  public LazyNumber eval(final LazyNumber v1, final LazyNumber v2) {
    if (v2 != null) {
      throw new ExpressionException("Did not expect a second parameter for unary operator");
    }
    return new LazyNumber() {
      @Override
      public String getString() {
        return String.valueOf(AbstractUnaryOperator.this.evalUnary(v1.eval()));
      }

      @Override
      public BigDecimal eval() {
        return AbstractUnaryOperator.this.evalUnary(v1.eval());
      }
    };
  }


  /**
   * Implementation of this operator calling unary operator evaluation method..
   *
   * @param v1 The first parameter.
   * @param v2 The second parameter. Expected to be null
   * @return The result of the operation.
   */
  public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
    if (v2 != null) {
      throw new ExpressionException("Did not expect a second parameter for unary operator");
    }
    return evalUnary(v1);
  }


  /**
   * Implementation of this prefix unary operator.
   *
   * @param v1 The parameter.
   * @return The result of the operation.
   */
  public abstract BigDecimal evalUnary(BigDecimal v1);
}