How to use

defineVariable

method

in

org.matheclipse.parser.client.eval.DoubleEvaluator

 public double evaluate(DoubleEvaluator engine, FunctionNode function) {
  if (function.size() != 3) {
   throw new ArithmeticException(
     "SetFunction#evaluate(DoubleEvaluator,FunctionNode) needs 2 arguments: "
       + function.toString());
  }
  if (!(function.getNode(1) instanceof SymbolNode)) {
   throw new ArithmeticException(
     "SetFunction#evaluate(DoubleEvaluator,FunctionNode) symbol required on the left hand side: "
       + function.toString());
  }
  String variableName = ((SymbolNode) function.getNode(1)).getString();
  double result = engine.evaluateNode(function.getNode(2));
  IDoubleValue dv = engine.getVariable(variableName);
  if (dv == null) {
   dv = new DoubleVariable(result);
  } else {
   dv.setValue(result);
  }
  engine.defineVariable(variableName, dv);
  return result;
 }
}

  /**
   * Evaluate.
   *
   * @param engine the engine
   * @param function the function
   * @return the double
   */
  @Override
  public double evaluate( DoubleEvaluator engine, FunctionNode function ) {
    if ( function.size() != 3 ) {
      throw new ArithmeticException( "SetFunction#evaluate(DoubleEvaluator,FunctionNode) needs 2 arguments: " + function.toString() );
    }
    if ( !(function.getNode( 1 ) instanceof SymbolNode) ) {
      throw new ArithmeticException( "SetFunction#evaluate(DoubleEvaluator,FunctionNode) symbol required on the left hand side: " + function.toString() );
    }
    String variableName = ((SymbolNode) function.getNode( 1 )).getString();
    double result = engine.evaluateNode( function.getNode( 2 ) );
    IDoubleValue dv = engine.getVariable( variableName );
    if ( dv == null ) {
      dv = new DoubleVariable( result );
    }
    else {
      dv.setValue( result );
    }
    engine.defineVariable( variableName, dv );
    return result;
  }
}

  @Override
  public double evaluate(DoubleEvaluator engine, FunctionNode function) {
    if (function.size() != 3) {
      throw new ArithmeticMathException(
          "SetFunction#evaluate(DoubleEvaluator,FunctionNode) needs 2 arguments: " + function.toString());
    }
    if (!(function.getNode(1) instanceof SymbolNode)) {
      throw new ArithmeticMathException(
          "SetFunction#evaluate(DoubleEvaluator,FunctionNode) symbol required on the left hand side: "
              + function.toString());
    }
    String variableName = ((SymbolNode) function.getNode(1)).getString();
    double result = engine.evaluateNode(function.getNode(2));
    IDoubleValue dv = engine.getVariable(variableName);
    if (dv == null) {
      dv = new DoubleVariable(result);
    } else {
      dv.setValue(result);
    }
    engine.defineVariable(variableName, dv);
    return result;
  }
}