I am working on implementing shunting yard algorithm in C#. Although it parses mathematical expressions with symbols( + , * – / and ^) pretty well.But for some reason it is not working for sine cosine functions . Like for example if I try to calculate sin(45) I get 0.707106 .
But when I try to parse expression like
sin(25)+cos(15+sin(25))+3 it gives me 0.43756 (Correct answer is: 2.19106879911)
sin(45)+cos(45) it gives me 0.715779 (Correct answer is: 1.414)
I have followed all the steps that are mentioned in this article at Wikipedia . I have trying this for a few days now but I am unable to make it work perfectly. Here is the main parsing function
private void parse()
{
//scan the input string
for (int j = 0; j < input.Length; j++)
{
if (Char.IsDigit(input[j])) //if its a number
{
string number = extractNumber(input, j); //extracts multiple digit number
j = currentposition; //increment the counter according to length of the digit
postfix += number + " ";
Console.WriteLine(postfix);
}
//if its a function character
else if(Char.IsLetter(input[j]) )
{
//its a letter
string function = getFunction(j); //get the function name
operators.Push( function );
j = currentposition;
}
else if(input[j] == ',') //if its a comma
{
while(operators.Peek() != "(")
{
postfix += input[j] + " ";
}
}
else if (IsAnOperator(input[j])) // if we have got an operator
{
if (operators.Count != 0 && IsHigherPrecedence(operators.Peek().ToCharArray()[0], input[j]))
{
while ( ( operators.Count != 0 && IsHigherPrecedence(operators.Peek().ToCharArray()[0], input[j]) ) )
{
postfix += operators.Pop() + " ";
}
}
operators.Push(Char.ToString(input[j]));
}
else if (input[j] == '(')
operators.Push(Char.ToString(input[j]));
else if (input[j] == ')')
{
while (operators.Count != 0 && operators.Peek() != "(")
postfix += operators.Pop() + " ";
operators.Pop();
}
} // end for loop
while(operators.Count > 0 )
postfix +=operators.Pop() + " ";
//Conversion Logic (postfix to final answer )
postfixtokens.AddRange( postfix.Split(' ') ) ;
for (int j = 0; j < postfixtokens.Count-1; j++)
{
if (IsAnOperator(postfixtokens[j][0]) && basket.Count > 1)
{
Double second = Double.Parse( basket.Pop() );
Double first = Double.Parse(basket.Pop() );
char op = postfixtokens[j][0];
Double result = ApplyOperation(op,second, first);
// Console.WriteLine("{0} {1} {2} = {3}", first, op, second, result);
basket.Push( result.ToString());
}
else if (IsAnOperator(postfixtokens[j][0]) && basket.Count == 1)
{
Double second = Double.Parse(basket.Pop());
Double first = 0.0;
char op = postfixtokens[j][0];
Double result = ApplyOperation(op, second, first);
// Console.WriteLine("{0} {1} {2} = {3}", first, op, second, result);
basket.Push(result.ToString() );
}
else if (Char.IsDigit(postfixtokens[j][0]))
{
basket.Push( postfixtokens[j] );
}
else if( isAFunction(postfixtokens[j]) )
{
//if its a single argument function
if (AllowedFunctions[postfixtokens[j]] == 1)
{
//single arg logic
if (postfixtokens[j] == "sin")
{
Double result = Math.Sin( Double.Parse(basket.Pop() )*Math.PI/180.0 );
//result = Math.PI / 180;
basket.Push(result.ToString());
}
else if (postfixtokens[j] == "cos")
{
Double result = Math.Cos( Double.Parse(basket.Pop() )*Math.PI/180.0 );
//result = Math.PI / 180;
basket.Push(result.ToString());
}
}
}
}
}
Moreover,
Here is the output of the program:
Input: 3+4*2/(1-5)^5^10
PostFix: 3 4 2 * 1 5 - 5 10 ^ ^ / +
Answer: 3
Input: 2+4
PostFix: 2 4 +
Answer: 6
Input Expression: -5-4
Input: -5-4
PostFix: 5 - 4 -
Answer: -9
Input: -4+3
PostFix: 4 - 3 +
Answer: -1
Input Expression: 4^(4^4)
Input: 4^(4^4)
PostFix: 4 4 4 ^ ^
Answer: 1.34078079299426E+154
Input: sin45
PostFix: 45 sin
Answer: 0.707106781186547 (correct)
//the faulty ones
Input: sin(25)+cos(15+sin(25))+3
PostFix: 25 15 25 sin + 3 + cos + sin
Answer: 0.437567038002202
Input: sin(45)+cos(45)
PostFix: 45 45 cos + sin
Answer: 0.71577935734684
New Cases:
Input: sin45+cos45
PostFix: 45 45 cos + sin
Answer: 0.71577935734684
Input: 2+sin30
PostFix: 2 30 sin +
Answer:2.5
Input: sin30+2
PostFix: 30 2 + sin
Answer: 0.529919264233205
Thats all.Can anybody point me what I am doing wrong.
Edit:
Here is the IsHigherPrecedance function and precedance enum
:
public enum Precedance { Plus =1,Minus=1,Multiply=2,Divide=2,Exponent=3,Unary = 4,Parenthesis=5 };
private bool IsHigherPrecedence(char a, char b)
{
Precedance f = getPrecedance(a);
Precedance s = getPrecedance(b);
if (f >= s)
return false;
else
return true;
}
public Precedance getPrecedance(char a)
{
if (a == '+')
return Precedance.Plus;
else if (a == '-')
return Precedance.Minus;
else if (a == '*')
return Precedance.Multiply;
else if (a == '/')
return Precedance.Divide;
else if (a == '^')
return Precedance.Exponent;
else if (Char.IsLetter(a))
return Precedance.Unary;
else if (a == '(' || a == ')')
return Precedance.Parenthesis;
else
return Precedance.Plus;
}
Now that these trigonometric function are single argument function, are they going to be parsed with some other logic or does this shunting yard algo works with such functions as well as well?
Regards.
There are a copule of problems here, but the primary one is that you are treating functions as operators, though they are not (intrinsic to this is that you call your stack “operators” as though that is the only thing that can be on it, not true). In particular, this branch:
needs to check to see if what’s on the “operators” stack is actually an operator:
Other issues include the branch that handles commas: