/// <summary>
/// This method gets called when the token parser encounters a minus sign in front of a value.
/// If the next token is a number, it will be changed to a negative number.
/// If the next token is a funcion, param, or equation, an equation will be generated that multiplies the result by -1
/// </summary>
/// <returns>The negative token.</returns>
/// <param name="tokenList">Token list.</param>
/// <param name="curIndex">Current index.</param>
/// <param name="owner">Owner.</param>
public static BaseNode ParseNegativeToken(List <Token> tokenList, ref int curIndex, Equation owner)
{
//verify that this is not the last token
if (curIndex >= (tokenList.Count - 1))
{
throw new FormatException("Can't end an equation with an operator");
}
//check that the token is a minus sign
if ("-" != tokenList[curIndex].TokenText)
{
throw new FormatException("Expected a value, but found an invalid operator instead: " + tokenList[curIndex].TokenText);
}
//skip past the minus sign so we can get to the next token
curIndex++;
//create a number node, parse the next token into it
BaseNode valueNode = BaseNode.ParseValueNode(tokenList, ref curIndex, owner);
Debug.Assert(null != valueNode); //TODO: throw exceptions
//what did we get back?
if (valueNode is NumberNode)
{
//the next node is a number, multiply it by minus one
NumberNode myNumberNode = valueNode as NumberNode;
myNumberNode.NumberValue *= -1.0f;
}
else
{
//ok the node was a function, param, or equation
//create another equation to multiply that resdult by -1
NumberNode negativeOne = new NumberNode();
negativeOne.NumberValue = -1.0f;
OperatorNode multiplyNode = new OperatorNode();
multiplyNode.Operator = '*';
//string it all together
negativeOne.AppendNextNode(multiplyNode);
multiplyNode.AppendNextNode(valueNode);
//put that into an equation node and treeify it
EquationNode myEquationNode = new EquationNode();
myEquationNode.SubEquation = negativeOne.Treeify();
Debug.Assert(null != myEquationNode.SubEquation); //TODO: throw exceptions
//set our result to the whole equation
valueNode = myEquationNode;
}
//return it as the result
return(valueNode);
}
/// <summary>
/// Given a list of tokens and the index, get an operator node based on whatever is at that index.
/// </summary>
/// <returns>The oper node, or null if it hit the end of the equation.</returns>
/// <param name="tokenList">Token list.</param>
/// <param name="curIndex">Current index.</param>
/// <param name="owner">the equation that this node is part of. required to pull function delegates out of the dictionary</param>
static protected BaseNode ParseOperNode(List <Token> tokenList, ref int curIndex, Equation owner)
{
if (null == tokenList)
{
throw new ArgumentNullException("tokenList");
}
if (null == owner)
{
throw new ArgumentNullException("owner");
}
Debug.Assert(curIndex < tokenList.Count); //TODO: throw exceptions
//what kind of token do I have at that index?
switch (tokenList[curIndex].TypeOfToken)
{
case TokenType.Operator:
{
//ok create an operator node
OperatorNode operNode = new OperatorNode();
//parse into that node
operNode.ParseToken(tokenList, ref curIndex, owner);
//return the thing
return(operNode);
}
case TokenType.CloseParen:
{
//close paren, just eat it and return null. It means this equation is finished parsing
curIndex++;
return(null);
}
default:
{
//should just be close paren nodes in here, which we should never get
throw new FormatException("Expected a \"operator\" token, but got a " + tokenList[curIndex].TypeOfToken.ToString());
}
}
}
