/// <summary>
/// Determines whether a parse tree can be plotted using a given set of variables.
/// <para/>
/// If the ParseTree contains any variables other than those specifiec in <c>variables</c>,
/// then this function will return false. Otherwise, it will return true.
/// </summary>
/// <param name="node">The ParseTreeNode to perform the recursive search on.</param>
/// <param name="variables">The variables to check for.</param>
/// <returns>Returns true if the ParseTreeNode can be plotted using the given variables; otherwise false.</returns>
public static bool CanPlotOverVariables(this ParseTreeNode node, params char[] variables)
{
if (node is BinaryParseTreeNode)
{
BinaryParseTreeNode binaryNode = node as BinaryParseTreeNode;
return(CanPlotOverVariables(binaryNode.Left, variables) && CanPlotOverVariables(binaryNode.Right, variables));
}
else if (node is UnaryParseTreeNode)
{
UnaryParseTreeNode unaryNode = node as UnaryParseTreeNode;
return(CanPlotOverVariables(unaryNode.Operand, variables));
}
else if (node is ConstantParseTreeNode)
{
return(true);
}
else if (node is VariableParseTreeNode)
{
// returns true if the VariableParseTreeNode's variable is in the variables array
// otherwise return false
return(Array.IndexOf(variables, (node as VariableParseTreeNode).Variable) != -1);
}
else
{
throw new InvalidOperationException("Unknown parse tree node type: " + node.GetType().Name);
}
}
/// <summary>
/// Determines whether a parse tree contains (refers to) a given variable.
/// </summary>
/// <param name="node">The ParseTreeNode to perform the recursive search on.</param>
/// <param name="variable">The variable to search for.</param>
/// <returns>Returns true if the ParseTreeNode contains the variable; false otherwise.</returns>
public static bool ContainsVariable(this ParseTreeNode node, char variable)
{
if (node is BinaryParseTreeNode)
{
BinaryParseTreeNode binaryNode = node as BinaryParseTreeNode;
return(ContainsVariable(binaryNode.Left, variable) || ContainsVariable(binaryNode.Right, variable));
}
else if (node is UnaryParseTreeNode)
{
UnaryParseTreeNode unaryNode = node as UnaryParseTreeNode;
return(ContainsVariable(unaryNode.Operand, variable));
}
else if (node is ConstantParseTreeNode)
{
return(false);
}
else if (node is VariableParseTreeNode)
{
return((node as VariableParseTreeNode).Variable == variable);
}
else
{
throw new InvalidOperationException("Unknown parse tree node type: " + node.GetType().Name);
}
}