/// <summary>
/// Makes expression tree from string
/// </summary>
/// <param name="ex"></param>
/// <returns></returns>
private Node MakeTree(string ex)
{
SolverUtilities.RemoveExternalBracets(ref ex);
Node res = new Node();
if (SolverUtilities.CheckNumber(ex))
{
res.Operation = ex;
res.Type = ExpressionType.Number;
res.Left = null;
res.Right = null;
}
if (SolverUtilities.CheckVariable(ex))
{
res.Operation = ex;
res.Type = ExpressionType.Variable;
res.Left = null;
res.Right = null;
}
if (SolverUtilities.CheckFunction(ex))
{
int openBracet, closeBracet;
openBracet = ex.IndexOf("(");
closeBracet = ex.LastIndexOf(")");
res.Operation = ex.Substring(0, openBracet);
string FunctionParam = ex.Substring(openBracet+1, closeBracet-openBracet-1);
// If function takes one argument then make one child node.
// If it takes two argumetns then make two children nodes;
if (SolverUtilities.NumberOfFunctionArguments(FunctionParam) == 1)
{
res.Type = ExpressionType.OneArgumentFunction;
res.Left = MakeTree(FunctionParam);
res.Right = null;
}
else
{
int comma = FunctionParam.IndexOf(",");
res.Type = ExpressionType.TwoArgumentFunction;
res.Left = MakeTree(FunctionParam.Substring(0, comma));
res.Right = MakeTree(FunctionParam.Substring(comma+1, FunctionParam.Length-comma-1));
}
}
// We should pay attention to operations' priorities
int signIndex = SolverUtilities.FindOperationSign(ex, new string[] {"-", "+"});
if (signIndex == -1)
signIndex = SolverUtilities.FindOperationSign(ex, new string[] {"/", "*"});
if (signIndex == -1)
signIndex = SolverUtilities.FindOperationSign(ex, new string[] { "^" });
if (signIndex != -1)
{
res.Operation = ex[signIndex].ToString();
res.Type = ExpressionType.Expression;
res.Left = MakeTree(ex.Substring(0, signIndex));
res.Right = MakeTree(ex.Substring(signIndex+1, ex.Length-signIndex-1));
}
return res;
}
/// <summary>
/// Figures out a value of given expression tree node
/// </summary>
/// <param name="tree"></param>
public void ExecuteTree(Node tree)
{
if (tree == null)
return;
ExecuteTree(tree.Left);
ExecuteTree(tree.Right);
switch (tree.Type)
{
case ExpressionType.Number:
tree.Value = double.Parse(tree.Operation);
break;
case ExpressionType.Variable:
if (!m_Variables.ContainsKey(tree.Operation))
return;
tree.Value = m_Variables[tree.Operation];
break;
case ExpressionType.Expression:
tree.Value = SolverUtilities.ExecuteExpression(tree.Operation, tree.Left.Value, tree.Right.Value);
break;
case ExpressionType.OneArgumentFunction:
tree.Value = SolverUtilities.ExecuteFunction(tree.Operation, tree.Left.Value);
break;
case ExpressionType.TwoArgumentFunction:
tree.Value = SolverUtilities.ExecuteFunction(tree.Operation, tree.Left.Value, tree.Right.Value);
break;
}
}
/// <summary>
/// Parsing string expression into expression tree
/// </summary>
public void Prepare()
{
// Check bracet balance
if (!SolverUtilities.CheckBracets(m_Expression))
return;
// Removing all spaces and make all characters low
m_Expression = m_Expression.ToLower().Replace(" ", string.Empty);
// Building an expression tree
ExpressionTree = MakeTree(m_Expression);
m_IsCompiled = true;
}