How to parse math expressions in C#? [duplicate] - c#

This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
Is there a string math evaluator in .NET?
Can C# parse mathematical expressions such as y=3*x + 3 into string? If so, ho?
I appreciate your help.


Here's a bit of code I wrote a while ago to parse infix (operator operand operator) equations.
There are some small classes and helper functions missing, but it should be fairly easy to implement them. If you need them or any help with it, let me know and I can upload them somewhere.
It's a basic implementation of Dijkstra's Shunting-yard algorithm
public Operand ExpressionTree
{
get;
private set;
}
private Stack<Operands.Operand> stack = new Stack<InfixParser.Operands.Operand>();
private Queue<Operands.Operand> outputQueue = new Queue<InfixParser.Operands.Operand>();
private void ParseFormulaString()
{
//Dijkstra's Shunting Yard Algorithm
Regex re = new Regex(#"([\+\-\*\(\)\^\/\ ])");
List<String> tokenList = re.Split(formulaString).Select(t => t.Trim()).Where(t => t != "").ToList();
for (int tokenNumber = 0; tokenNumber < tokenList.Count(); ++tokenNumber)
{
String token = tokenList[tokenNumber];
TokenClass tokenClass = GetTokenClass(token);
switch (tokenClass)
{
case TokenClass.Value:
outputQueue.Enqueue(new Value(token));
break;
case TokenClass.Function:
stack.Push(new Function(token, 1));
break;
case TokenClass.Operator:
if (token == "-" && (stack.Count == 0 || tokenList[tokenNumber - 1] == "("))
{
//Push unary operator 'Negative' to stack
stack.Push(new Negative());
break;
}
if (stack.Count > 0)
{
String stackTopToken = stack.Peek().Token;
if (GetTokenClass(stackTopToken) == TokenClass.Operator)
{
Associativity tokenAssociativity = GetOperatorAssociativity(token);
int tokenPrecedence = GetOperatorPrecedence(token);
int stackTopPrecedence = GetOperatorPrecedence(stackTopToken);
if (tokenAssociativity == Associativity.Left && tokenPrecedence <= stackTopPrecedence ||
tokenAssociativity == Associativity.Right && tokenPrecedence < stackTopPrecedence)
{
outputQueue.Enqueue(stack.Pop());
}
}
}
stack.Push(new BinaryOperator(token, Operator.OperatorNotation.Infix));
break;
case TokenClass.LeftParen:
stack.Push(new LeftParenthesis());
break;
case TokenClass.RightParen:
while (!(stack.Peek() is LeftParenthesis))
{
outputQueue.Enqueue(stack.Pop());
}
stack.Pop();
if (stack.Count > 0 && stack.Peek() is Function)
{
outputQueue.Enqueue(stack.Pop());
}
break;
}
if (tokenClass == TokenClass.Value || tokenClass == TokenClass.RightParen)
{
if (tokenNumber < tokenList.Count() - 1)
{
String nextToken = tokenList[tokenNumber + 1];
TokenClass nextTokenClass = GetTokenClass(nextToken);
if (nextTokenClass != TokenClass.Operator && nextTokenClass != TokenClass.RightParen)
{
tokenList.Insert(tokenNumber + 1, "*");
}
}
}
}
while (stack.Count > 0)
{
Operand operand = stack.Pop();
if (operand is LeftParenthesis || operand is RightParenthesis)
{
throw new ArgumentException("Mismatched parentheses");
}
outputQueue.Enqueue(operand);
}
String foo = String.Join(",", outputQueue.Select(t => t.Token).ToArray());
String bar = String.Join("", tokenList.ToArray());
Stack<Operand> expressionStack = new Stack<Operand>();
while (outputQueue.Count > 0)
{
Operand operand = outputQueue.Dequeue();
if (operand is Value)
{
expressionStack.Push(operand);
}
else
{
if (operand is BinaryOperator)
{
BinaryOperator op = (BinaryOperator)operand;
Operand rightOperand = expressionStack.Pop();
Operand leftOperand = expressionStack.Pop();
op.LeftOperand = leftOperand;
op.RightOperand = rightOperand;
}
else if (operand is UnaryOperator)
{
((UnaryOperator)operand).Operand = expressionStack.Pop();
}
else if (operand is Function)
{
Function function = (Function)operand;
for (int argNum = 0; argNum < function.NumArguments; ++argNum)
{
function.Arguments.Add(expressionStack.Pop());
}
}
expressionStack.Push(operand);
}
}
if (expressionStack.Count != 1)
{
throw new ArgumentException("Invalid formula");
}
ExpressionTree = expressionStack.Pop();
}
private TokenClass GetTokenClass(String token)
{
double tempValue;
if (double.TryParse(token, out tempValue) ||
token.Equals("R", StringComparison.CurrentCultureIgnoreCase) ||
token.Equals("S", StringComparison.CurrentCultureIgnoreCase))
{
return TokenClass.Value;
}
else if (token.Equals("sqrt", StringComparison.CurrentCultureIgnoreCase))
{
return TokenClass.Function;
}
else if (token == "(")
{
return TokenClass.LeftParen;
}
else if (token == ")")
{
return TokenClass.RightParen;
}
else if (binaryInfixOperators.Contains(token))
{
return TokenClass.Operator;
}
else
{
throw new ArgumentException("Invalid token");
}
}
private Associativity GetOperatorAssociativity(String token)
{
if (token == "^")
return Associativity.Right;
else
return Associativity.Left;
}
private int GetOperatorPrecedence(String token)
{
if (token == "+" || token == "-")
{
return 1;
}
else if (token == "*" || token == "/")
{
return 2;
}
else if (token == "^")
{
return 3;
}
else
{
throw new ArgumentException("Invalid token");
}
}


Possibly a duplicate of:
Is there a string math evaluator in .NET?
The short answer is no, for the long answer see the link. ( I recommend 'coppercoders' solution. )


Why don't you use Simple Math Parser or something is same?
link text


I took a cheap way out in a recent Silverlight application by scrubbing the string with a regex (for safety) and passing it to the JavaScript evaluator. It actually works very well but it's a hack I admit.
http://josheinstein.com/blog/index.php/2010/03/mathevalconverter

Related

ICollectionView multiple filter

So I have a fitler TextBox where I want to search for different type of docs in a grid the code where I have different type of columns such as: Date,DocId,ClientId.
For a search I write on a filter Textbox something like that DocId:2002 and It just work fine but when I try to make a multiple search for example DocId:2002 ClientId:201 It doesnt search because of the return it just does an infinite loop.
private void TextBoxFilter_TextChanged(object sender, TextChangedEventArgs e)
{
foreach (Match m in Regex.Matches((sender as TextBox).Text, pattern, options))
{
if (m.Value != "")
{
Func<String, String> untilSlash = (s) => { return filters[re.Match(s).Groups[1].ToString()] = re.Match(s).Groups[2].ToString(); };
untilSlash(m.Value);
}
}
ICollectionView cv = CollectionViewSource.GetDefaultView(this.DataGridDocList.ItemsSource);
if (filters.Count == 0)
{
cv.Filter = null;
}
else
{
cv.Filter = o =>
{
for (int i = 0; i < filters.Count; i++)
{
if (filters.ElementAt(i).Key == "Date")
{
if (DateVerify.Match(filters.ElementAt(i).Value).Success)
{
return (o as Document).DateCreated < Convert.ToDateTime(DateVerify.Match(filters.ElementAt(i).Value).Groups[1].ToString()) && (o as Document).DateCreated > Convert.ToDateTime(DateVerify.Match(filters.ElementAt(i).Value).Groups[2].ToString());
}
else
{
var dateString = (o as Document).DateCreated.ToString("dd/MM/yyyy", CultureInfo.InvariantCulture);
return dateString.Contains(DateVerify.Match(filters.ElementAt(i).Value).Groups[1].ToString());
}
}
if (filters.ElementAt(i).Key == "DocId")
{
return (o as Document).DocumentId.ToString().Contains(filters.ElementAt(i).Value);
}
if (filters.ElementAt(i).Key == "ClientId")
{
return (o as Document).ClientId.ToUpper().Contains(filters.ElementAt(i).Value.ToUpper());
}
}
return false;
};
filters.Clear();
}
}
So my question is how can I do an big search with all the filters at one time?
Manually I can add them 1 by 1 and it will be something like search1 && search2 && search3 but It will take too much time and It's probably not the best solution

There are many ways of building up the predicate. However my suggestion is to keep it simple and just create one method that returns true or false. It's good practice to only return once in a method.
The code below if for illustration purposes (as I'm unable to test it):
ICollectionView cv = CollectionViewSource.GetDefaultView(this.DataGridDocList.ItemsSource);
if (filters.Any())
{
cv.Filter = new Predicate<object>(PredicateFilter);
}
else
{
cv.Filter = null;
}
Then Predicate method to filter results:
public bool PredicateFilter(object docObj)
{
Document doc = docObj as Document;
var response = new List<bool>();
for (int i = 0; i < filters.Count; i++)
{
if (filters.ElementAt(i).Key == "Date")
{
if (DateVerify.Match(filters.ElementAt(i).Value).Success)
{
response.Add(doc.DateCreated < Convert.ToDateTime(DateVerify.Match(filters.ElementAt(i).Value).Groups[1].ToString()) && doc.DateCreated > Convert.ToDateTime(DateVerify.Match(filters.ElementAt(i).Value).Groups[2].ToString()));
}
else
{
var dateString = doc.DateCreated.ToString("dd/MM/yyyy", CultureInfo.InvariantCulture);
response.Add(dateString.Contains(DateVerify.Match(filters.ElementAt(i).Value).Groups[1].ToString()));
}
}
else if (filters.ElementAt(i).Key == "DocId")
{
response.Add(doc.DocumentId.ToString().Contains(filters.ElementAt(i).Value));
}
else if (filters.ElementAt(i).Key == "ClientId")
{
response.Add(doc.ClientId.ToUpper().Contains(filters.ElementAt(i).Value.ToUpper()));
}
}
return response.All(m => m); // if all filters came back with true, return 1 response of true else false.
}

code throws NullReferenceException when add an item to dictionary inside factory startnew

I have C# code; when run to a line, it throws a System.NullReferenceException.
Here is the line of the code that cause the exception
if (expDic != null && expression != null)
{
expDic.Add(i, expression.ToString())
}
Here is the stack trace in the code
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at Sustainability.BusinessObject.CalculationManager.<>c__DisplayClass18_0.<HandleFormulaInner>b__0(Object args) in D:\HK\Desktop\VSTS_2\Sustainability.BusinessObject\Classes\CalculationManager.cs:line 1410
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
I found that both expDic and expression are not null, however it throws a null reference exception.
Here is my code:
int count = table.Rows.Count;
Dictionary<int, string> expDic = new Dictionary<int, string>();
List<Task> taskList = new List<Task>();
for (int f = 0; f < count; f++)
{
DataRow tempformula = table.Rows[f];
string formulaSymbol = Convert.ToString(tempformula[Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
var t = Task.Factory.StartNew(new Action<object>((args) => {
int i = (int)args;
_sem.Wait();
StringBuilder expression = new StringBuilder(1024);
using (DataTable dt = new DataTable())
{
// symbol in the last line of formula
if (exp.EndsWith("+")
|| exp.EndsWith("-")
|| exp.EndsWith("*")
|| exp.EndsWith("/"))
{
exp = exp.Substring(0, exp.Length - 1);
}
object result = dt.Compute(exp, "");
expression.Append(result);
}
}
{
if (!string.IsNullOrWhiteSpace(symbol)
&& expression.Length > 0)
{
if (i + 1 >= count && symbol != ")")
{
}
else if (expression.ToString() != symbol)
{
expression.Append(symbol);
}
}
else if (expression.Length == 0 && symbol == "(")
{
expression.Append(symbol);
}
if (symbol == "days")
{
// calculating average values by days.
if (fromDate != null && toDate != null)
{
int days = toDate.Value.Subtract(fromDate.Value).Days + 1;
expression.Append(days);
}
else
{
expression.Append(1);
}
}
}
//Here is the code will have problem
if (expDic != null && expression != null)
{
expDic.Add(i, expression.ToString());
}
_sem.Release();
}), f);
taskList.Add(t);
}
I am doubting it is caused by the StartNew multithreading pattern,
so what is wrong in my code and how can I fix it?

What is the value of arg in Task.Factory.StartNew

I have Task.Factory.StartNew in C# code with args argument. I am not quite understand what value will arg be. So what value will args be and how the value is determined?
int count = table.Rows.Count;
Dictionary<int, string> expDic = new Dictionary<int, string>();
List<Task> taskList = new List<Task>();
for (int f = 0; f < count; f++)
{
DataRow tempformula = table.Rows[f];
string formulaSymbol = Convert.ToString(tempformula[Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
var t = Task.Factory.StartNew(new Action<object>((args) => {
int i = (int)args;
_sem.Wait();
StringBuilder expression = new StringBuilder(1024);
DataRow formula = table.Rows[i];
int indID = Convert.ToInt32(formula[Common.Systems.Sustainability.Constants.IndicatorFormula.IndicatorID]);
int sequence = Convert.ToInt32(formula[Common.Systems.Sustainability.Constants.IndicatorFormula.Sequence]);
int? referenceIndID = Common.Util.TryToConvertToInt32(formula, Common.Systems.Sustainability.Constants.IndicatorFormula.ReferenceIndicatorID);
decimal? val = Common.Util.TryToConvertToDecimal(formula, Common.Systems.Sustainability.Constants.IndicatorFormula.Value);
string symbol = Convert.ToString(formula[Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
string formulaOutputUnit = Convert.ToString(formula[Common.Systems.Sustainability.Constants.Indicator.Unit]);
if (!string.IsNullOrWhiteSpace(callerAcceptedUnit)) // added by HC on 2016-05-27
{
formulaOutputUnit = callerAcceptedUnit;
}
if (referenceIndID == null)
{
if (val == null)
{
DataSet indicator = GetIndicatorByIDFromCache(companyID, indID); // added by HC on 2017-05-12, for performance tuning.
//using (DataSet indicator = indicatorMgr.GetIndicatorByID(companyID, indID))
{
DataRow dr = indicator.Tables[0].Rows[0];
int indicatorType = Convert.ToInt32(dr[Common.Systems.Sustainability.Constants.Indicator.IndicatorType]);
if (indicatorType == (int)Common.Systems.Sustainability.Constants.IndicatorTypes.Currency
|| indicatorType == (int)Common.Systems.Sustainability.Constants.IndicatorTypes.Numeric)
{
decimal? total = SumTotal(companyID, indID, indicatorType, fromDate, toDate, formulaOutputUnit, callerIndicatorID, breakToMonthly, specifiedLocations, approvalStatus
, usageDataSet, interval
, indicatorIDsChain
, allowNull
);
expression.Append(total.ToString());
}
else if (symbol == "+"
|| symbol == "-"
|| symbol == "*"
|| symbol == "/")
{
expression.Append(symbol);
}
}
}
else
{
expression.Append(val.ToString());
}
}
else
{
string exp = GetExpression(companyID, fromDate, toDate, referenceIndID.Value.ToString(), indID.ToString(), formulaOutputUnit, breakToMonthly, specifiedLocations, approvalStatus
, usageDataSet, interval
, indicatorIDsChain
);
//expression.Append(exp);
using (DataTable dt = new DataTable())
{
// fault tolerance, for in-case users assigned symbol in the last line of formula
if (exp.EndsWith("+")
|| exp.EndsWith("-")
|| exp.EndsWith("*")
|| exp.EndsWith("/"))
{
exp = exp.Substring(0, exp.Length - 1);
}
object result = dt.Compute(exp, "");
expression.Append(result);
}
} // end if (referenceIndID == null)...
if ("IF".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "THEN".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "ELSE IF".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "ELSE".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| ">".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| ">=".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "=".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "<=".Equals(symbol, StringComparison.OrdinalIgnoreCase)
|| "<".Equals(symbol, StringComparison.OrdinalIgnoreCase)
)
{
//--------------------------------------------------------
// Begin, added by HC on 2016-12-14
// as requested by CQS users, add "IF" statement for GRI indicators
string exp = HandleIFCondition(table, i, companyID, fromDate, toDate, indicatorIDs, callerIndicatorID, callerAcceptedUnit, breakToMonthly, specifiedLocations, approvalStatus, usageDataSet, interval, indicatorIDsChain);
expression.Append(exp);
// End, added by HC on 2016-12-14
//--------------------------------------------------------
// Find End if, added by Alex Poon on 20190306
int ifIndex = i;
for (var j = ifIndex; j < count; j++)
{
string endIfSymbol = Convert.ToString(table.Rows[j][Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
if ("END IF".Equals(endIfSymbol, StringComparison.OrdinalIgnoreCase))
{
i = j;
break;
}
}
}
else
{
if (!string.IsNullOrWhiteSpace(symbol)
&& expression.Length > 0 // added by HC on 2016-06-24
)
{
if (i + 1 >= count && symbol != ")")
{
// ignore the symbol
}
else if (expression.ToString() != symbol)
{
expression.Append(symbol);
}
}
else if (expression.Length == 0 && symbol == "(")
{
expression.Append(symbol);
}
if (symbol == "days")
{
// added by HC on 2017-01-23, a new requirements for calculating average values by days.
if (fromDate != null && toDate != null)
{
int days = toDate.Value.Subtract(fromDate.Value).Days + 1;
expression.Append(days);
}
else
{
expression.Append(1);
}
}
} // end if ("IF".Equals(symbol, StringComparison.OrdinalIgnoreCase)...
if (expDic != null && expression != null)
{
expDic.Add(i, expression.ToString());
}
_sem.Release();
}), f);
taskList.Add(t);
if ("IF".Equals(formulaSymbol, StringComparison.OrdinalIgnoreCase))
{
for (var j = f; j < count; j++)
{
string endIfSymbol = Convert.ToString(table.Rows[j][Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
if ("END IF".Equals(endIfSymbol, StringComparison.OrdinalIgnoreCase))
{
f = j;
break;
}
}
}
}
Task.WaitAll(taskList.ToArray());
List<int> keys = expDic.Keys.ToList();
keys.Sort();
string finalExpression = "";
foreach (var key in keys)
{
finalExpression += expDic[key];
}
return finalExpression;
}

args in your case is data that will be passed to a delegate specified by Action<object> parameter.
See docs.
When using overload of StartNew with Action<object>, you need to supply next argument of type object, which will be used in passed delegate.
Task.Factory.StartNew((o) => {/* 1 will be used here */}, 1, token, options, scheduler);

MSDN
The args argument (referred to as "state" in the documentation) is a parameter you need to specify when you call to Task.Factory.StartNew.
state (Object): An object containing data to be used by the action delegate.
Sample:
object param = somevalue;
Task.Factory.StartNew( (arg) =>
{ /* get the arg value here.*/
}, param);

Parse complex TypeName from a String in C#

From a CompactFramework, I got a TypeString which can be a complex type, meaning it can use generics, arrays, etc. That means it can look like Sytem.Tuple’1[[Sytem.String, mscorlib]]. Problem is, I can not use Type.GetType because the assemblys in the Typestring may be wrong or not present.
Is there a lib which parses the string, and returns a type by searching all types in appdomain for the right one?

I've now found no Code, but solved using this:
public static class TypeHelper
{
public static Type GetTypeFromString(string typeString)
{
int pos = 0;
return ParseInternal(typeString, ref pos);
}
private static Type ParseInternal(string name, ref int pos)
{
StringBuilder sb = new StringBuilder();
List<Type> genericParameters = null;
int arrayDimensions = 0;
bool ignore = false;
while (pos < name.Length)
{
char c = name[pos++];
switch (c)
{
case ',':
{
if (arrayDimensions > 0)
arrayDimensions++;
else
ignore = true;
break;
}
case '[':
{
if (name[pos] == '[')
{
if (genericParameters == null)
genericParameters = new List<Type>();
pos++;
genericParameters.Add(ParseInternal(name, ref pos));
}
else if (genericParameters!=null)
genericParameters.Add(ParseInternal(name, ref pos));
else
arrayDimensions++;
break;
}
case ']':
{
var currentName = sb.ToString();
var type = AppDomain.CurrentDomain.GetAssemblies().SelectMany(x => x.GetTypes()).FirstOrDefault(x => x.FullName == currentName);
if (name.Length > pos && name[pos] == ']')
{
pos++;
}
if (genericParameters != null)
{
return type.MakeGenericType(genericParameters.ToArray());
}
else if (arrayDimensions != 0)
{
return type.MakeArrayType(arrayDimensions);
}
return type;
}
default:
if (!ignore)
sb.Append(c);
continue;
}
}
{
var currentName = sb.ToString();
var type = AppDomain.CurrentDomain.GetAssemblies().SelectMany(x => x.GetTypes()).FirstOrDefault(x => x.FullName == currentName);
if (genericParameters != null)
{
return type.MakeGenericType(genericParameters.ToArray());
}
else if (arrayDimensions != 0)
{
return type.MakeArrayType(arrayDimensions);
}
return type;
}
}
}

Shunting Yard Algorithm in C# only works some of the time

I am working on building an expression tree from an infix expression. Currently I am converting to postfix and then building the tree. My code works for most expressions but not all. I am doing something wrong with my implementation of parentheses. Here is my code-
readonly static char[] operators = { '+', '-', '*', '/' };
string order_of_op(string op1, string op2)
{
if (op1 == "*" || op1 == "/")//is op1 higher?
{
return op1;//it is so return it
}
else if ((op2 == "*" || op2 == "/"))//is op2 higher
{
return op2;//it is so return it
}
else
return op1;// they are both addition or subtraction so return op1.
}
Queue<string> convert_to_postfix(string infix) //following the Shunting-yard algorithm
{
Queue<string> num_queue = new Queue<string>();
Stack<string> op_stack = new Stack<string>();
Stack<string> temp_stack = new Stack<string>();
string temp = "";
foreach (char s in infix)
{
if (operators.Contains(s) == true)//if its a function push it on the stack
{
if (temp != "")//make sure we don't push an empty string
num_queue.Enqueue(temp);
if (op_stack.Count != 0)//make sure we dont crash popping from empty stack
{
if (op_stack.Peek() != "(")//if we dont have a parenthese on top proceed as normal
{
if (op_stack.Count > 1)
{
while (op_stack.Count != 0 && order_of_op(op_stack.Peek(), s.ToString()) == op_stack.Peek())
{
num_queue.Enqueue(op_stack.Pop());
}
}
}
op_stack.Push(s.ToString());
}
else
{
op_stack.Push(s.ToString());
}
temp = "";
}
else if (s == '(')
{
op_stack.Push(s.ToString());
}
else if (s == ')')
{
if (temp!= "")
num_queue.Enqueue(temp);
temp = "";
while (op_stack.Peek() != "(")
{
num_queue.Enqueue(op_stack.Pop());
}
op_stack.Pop();
if (op_stack.Count > 1)
{
if (operators.Contains(op_stack.Peek()[0]) == true)
{
num_queue.Enqueue(op_stack.Pop());
}
}
}
else
{
temp += s;
}
}
if (temp != "")
{
num_queue.Enqueue(temp);
}
foreach (string s in op_stack)
{
num_queue.Enqueue(s);
}
Console.Write("Postfix = ");
foreach (string s in num_queue)
{
Console.Write(s);
}
Console.WriteLine();
return num_queue;
}
Thank you for any help!

Well I fixed it! All I had to change was-
if (op_stack.Count > 1)
to
if (op_stack.Count >= 1)

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