ParseTreeNode FunctionCall()
{
FunctionParseTreeNode node = new FunctionParseTreeNode();
if (!tokens.HasNext())
{
throw new Exception("Synax error: Expecting function identifieri at token " + tokens.Position);
}
node.Token = tokens.Forward();
if (!tokens.HasNext() || tokens.PeekForward().TokenType != TokenIdentifier.TokenType.LeftParenthesis)
{
throw new Exception("Synax error: Expecting function identifieri at token " + tokens.Position);
}
tokens.Forward();
bool expect = false;
while (tokens.HasNext())
{
if (tokens.PeekForward().TokenType == TokenIdentifier.TokenType.RightParenthesis)
{
tokens.Forward();
return(node);
}
if (expect && tokens.PeekForward().TokenType == TokenIdentifier.TokenType.ParamSeparator)
{
tokens.Forward();
expect = false;
}
else
{
node.Parameters.Add(Expr());
expect = true;
}
}
throw new Exception("Syntax error: Expecting function end ')' at token " + tokens.Position);
}
private double Evaluate(ParseTreeNode node)
{
if (node is LeftOperatorNode)
{
// left operators
if (node.Token.TokenType == TokenIdentifier.TokenType.MinusOperator)
{
// minus
return(-Evaluate(((LeftOperatorNode)node).Next));
}
else if (node.Token.TokenType == TokenIdentifier.TokenType.NegationOperator)
{
// negation
return(~(long)Evaluate(((LeftOperatorNode)node).Next));
}
else
{
// factorial
double value = Evaluate(((LeftOperatorNode)node).Next);
double newValue = 1;
while (value > 1)
{
newValue *= value--;
}
return(newValue);
}
}
else if (node is FunctionParseTreeNode)
{
// we have a function
FunctionParseTreeNode n = (FunctionParseTreeNode)node;
string name = ((IdentifierToken)n.Token).Identifier;
if (functions.ContainsKey(name))
{
if (n.Parameters.Count < functions[name].MinArgs)
{
throw new Exception("The function needs at least " + functions[name].MinArgs + " argument(s).");
}
double[] parValues = new double[n.Parameters.Count];
for (int i = 0; i < n.Parameters.Count; i++)
{
parValues[i] = Evaluate(n.Parameters[i]);
}
return(functions[name].FunctionCallback(parValues));
}
else
{
throw new Exception("The function '" + name + "' does not exist.");
}
}
else
{
if (node.Left != null)
{
// we have an operator
double first = Evaluate(node.Left);
double second = Evaluate(node.Right);
switch (node.Token.TokenType)
{
case TokenIdentifier.TokenType.MinusOperator: return(first - second);
case TokenIdentifier.TokenType.PlussOperator: return(first + second);
case TokenIdentifier.TokenType.MultiplicationOperator: return(first * second);
case TokenIdentifier.TokenType.DivisionOperator: return(first / second);
case TokenIdentifier.TokenType.ModuloOperator: return(first % second);
case TokenIdentifier.TokenType.AndOperator: return((int)first & (int)second);
case TokenIdentifier.TokenType.XorOperator: return((int)first ^ (int)second);
case TokenIdentifier.TokenType.OrOperator: return((int)first | (int)second);
case TokenIdentifier.TokenType.ShiftLeftOperator: return((int)first << (int)second);
case TokenIdentifier.TokenType.ShiftRightOperator: return((int)first >> (int)second);
case TokenIdentifier.TokenType.PowerOperator: return(Math.Pow(first, int.Parse(second.ToString())));
}
}
else if (node.Token.TokenType == TokenIdentifier.TokenType.Identifier)
{
// we have a variable name
string name = ((IdentifierToken)node.Token).Identifier;
if (variables.ContainsKey(name))
{
return(variables[name]);
}
else
{
throw new Exception("There exists no variables with the name '" + name + "'.");
}
}
return(((NumberToken)node.Token).Value);
}
}
