public decimal Evaluate()
{
try
{
if (Value is VariableReference)
{
return((Value as VariableReference).Variable.Value);
}
if (Value is AssignmentOperator)
{
IVariable var = Children[0].Value as IVariable;
if (var == null)
{
throw new InvalidOperationException("The left-hand side of an assignment must be a variable.");
}
return((Value as AssignmentOperator).Invoke(var, Children[1].Evaluate()));
}
if (Value is ILiteral)
{
return((Value as ILiteral).Value);
}
if (Value is IConstant)
{
return((Value as IConstant).Value);
}
if (Value is UnknownVariable)
{
if (_parsedExpression.EvaluateUndefinedVariable == null)
{
throw new InvalidOperationException(string.Format("Cannot evaluate the value of ‘{0}’ variable.", Value.Name));
}
return((Value as UnknownVariable).Value = _parsedExpression.EvaluateUndefinedVariable(Value.Name));
}
if (Value is IVariable)
{
return((Value as IVariable).Value);
}
if (Value is IUnaryOperator)
{
return((Value as IUnaryOperator).Invoke(Children[0].Evaluate()));
}
if (Value is IBinaryOperator)
{
return((Value as IBinaryOperator).Invoke(Children[0].Evaluate(), Children[1].Evaluate()));
}
if (Value is UnknownFunction)
{
if (_parsedExpression.EvaluateUndefinedFunction == null)
{
throw new InvalidOperationException(string.Format("Cannot evaluate the value of ‘{0}’ function.", Value.Name));
}
IFunction func = Value as IFunction;
if (Children.Count != func.ParametersCount)
{
throw new ArgumentException(string.Format("There is no function ‘{0}’ with {1} parameters defined.", func.Name, func.ParametersCount));
}
return(_parsedExpression.EvaluateUndefinedFunction(Value.Name, Children.Select(node => node.Evaluate()).ToArray()));
}
if (Value is IStatement)
{
IStatement statement = Value as IStatement;
if (Children.Count != statement.ParametersCount)
{
throw new ArgumentException(string.Format("There is no statement ‘{0}’ with {1} parameters defined.", statement.Name, statement.ParametersCount));
}
return(statement.Invoke(Children.Cast <IEvaluableElement>().ToArray()));
}
if (Value is IFunction)
{
IFunction func = Value as IFunction;
if (Children.Count != func.ParametersCount)
{
throw new ArgumentException(string.Format("There is no function ‘{0}’ with {1} parameters defined.", func.Name, func.ParametersCount));
}
return(func.Invoke(Children.Select(node => node.Evaluate()).ToArray()));
}
throw new ArgumentException(string.Format("Unexpected element: ‘{0}’.", Value.Name));
}
catch (ArithmeticException)
{
if (_parsedExpression.ZeroOnError)
{
return(0m);
}
throw;
}
}