} // method
public static int Evaluate(string postfixNotationString)
{
if (string.IsNullOrWhiteSpace(postfixNotationString)) throw new ArgumentException("Argument postfixNotationString must not be null, empty or whitespace.", "postfixNotationString");
Stack<string> stack = new Stack<string>();
string sanitizedString = new string(postfixNotationString.Where(c => AllowedCharacters.Contains(c)).ToArray());
List<string> enumerablePostfixTokens = sanitizedString.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
foreach (string token in enumerablePostfixTokens)
{
if (token.Length > 0)
{
if (token.Length > 1)
{
if (!StaticStrings.IsNumeric(token)) throw new Exception("Operators and operands must be separated by a space.");
stack.Push(token);
}
else
{
char tokenChar = token[0];
if (StaticStrings.Numbers.Contains(tokenChar))
{
stack.Push(tokenChar.ToString());
}
else if (StaticStrings.Operators.Contains(tokenChar))
{
if (stack.Count < 2) throw new FormatException("The algebraic string has not sufficient values in the expression for the number of operators.");
string r = stack.Pop();
string l = stack.Pop();
int rhs = int.MinValue;
int lhs = int.MinValue;
bool parseSuccess = int.TryParse(r, out rhs);
parseSuccess &= int.TryParse(l, out lhs);
parseSuccess &= (rhs != int.MinValue && lhs != int.MinValue);
if (!parseSuccess) throw new Exception("Unable to parse valueStack characters to Int32.");
int value = int.MinValue;
if (tokenChar == '+')
{
value = lhs + rhs;
}
else if (tokenChar == '*')
{
value = lhs * rhs;
}
if (value != int.MinValue)
{
stack.Push(value.ToString());
}
else throw new Exception("Value never got set.");
}
else throw new Exception(string.Format("Unrecognized character '{0}'.", tokenChar));
}
}
else throw new Exception("Token length is less than one.");
}
if (stack.Count == 1)
{
int result = 0;
if (!int.TryParse(stack.Pop(), out result)) throw new Exception("Last value on stack could not be parsed into an integer.");
return result;
}
else throw new Exception("The input has too many values for the number of operators.");
} // method
public static Expression<Func<int>> ExpressionTree(string postfixNotationString)
{
if (string.IsNullOrWhiteSpace(postfixNotationString))
{
throw new ArgumentException("Argument postfixNotationString must not be null, empty or whitespace.", "postfixNotationString");
}
Stack<Expression> stack = new Stack<Expression>();
string sanitizedString = new string(postfixNotationString.Where(c => AllowedCharacters.Contains(c)).ToArray());
List<string> enumerablePostfixTokens = sanitizedString.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
foreach (string token in enumerablePostfixTokens)
{
if (token.Length < 1) throw new Exception("Token.Length is less than one.");
int tokenValue = 0;
bool parseSuccess = int.TryParse(token, out tokenValue);
if (token.Length > 1) // Numbers > 10 will have a token length > 1
{
if (!StaticStrings.IsNumeric(token) || !parseSuccess)
{
throw new Exception("Operators and operands must be separated by a space.");
}
stack.Push(Expression.Constant(tokenValue));
}
else
{
char tokenChar = token[0];
if (StaticStrings.Numbers.Contains(tokenChar) && parseSuccess)
{
stack.Push(Expression.Constant(tokenValue));
}
else if (StaticStrings.Operators.Contains(tokenChar))
{
// There must be two operands for the operator to operate on
if (stack.Count < 2) throw new FormatException("The algebraic string has not sufficient values in the expression for the number of operators; There must be two operands for the operator to operate on.");
Expression left = stack.Pop();
Expression right = stack.Pop();
Expression operation = null;
// ^ token uses Math.Pow, which both gives and takes double, hence convert
if (tokenChar == '^')
{
left = ConvertExpressionType(left, typeof(double));
right = ConvertExpressionType(right, typeof(double));
}
else // Math.Pow returns a double, so we must check here for all other operators
{
left = ConvertExpressionType(left, typeof(int));
right = ConvertExpressionType(right, typeof(int));
}
switch (tokenChar)
{
case '+': operation = Expression.AddChecked(left, right); break;
case '-': operation = Expression.SubtractChecked(left, right); break;
case '*': operation = Expression.MultiplyChecked(left, right); break;
case '/': operation = Expression.Divide(left, right); break;
case '^': operation = Expression.Power(left, right); break;
default: throw new Exception(string.Format("Unrecognized character '{0}'.", tokenChar));
}
stack.Push(operation);
}
else throw new Exception(string.Format("Unrecognized character '{0}'.", tokenChar));
}
}
if (stack.Count != 1) throw new Exception("The input has too many values for the number of operators.");
return Expression.Lambda<Func<int>>(stack.Pop());
} // method
