Can I get comments added to this code; so that I can understand it better? and any other useful comments or information to infrom me of the code specifically.

#include

#include

#include

#include

using namespace std;

string InfixToPostfix(string expression);

int evaluatePostfix(string exp);

int HasHigherPrecedence(char operator1, char operator2);

// Function to verify whether a character is a operator symbol or not.

bool IsOperator(char C);

// Function to verify whether a character is alphanumeric chanaracter (letter or numeric digit) or not.

bool IsOperand(char C);

int main(int argc, char *argv[])

{

// system("cls");

string expression;

cout << "1.Enter Infix Expression ";

cout << "2.Enter Postfix Expression ";

int n;

cout << "Enter choice:";

cin >> n;

cout<<"Enter expression: ";

cin.ignore();

getline(cin, expression);

if (n == 1){

string postfix = InfixToPostfix(expression);

cout << "Output = " << postfix << " ";

int k = evaluatePostfix(postfix);

cout << "Result: " << evaluatePostfix(postfix) << endl;

}

else if (n == 2){

cout << "Result: " << evaluatePostfix(expression) << endl;

}

// system("PAUSE");

return 0;

}

// Function to evaluate postfix expression and return output

string InfixToPostfix(string expression)

{

// Declaring a stack

stack S;

string postfix = ""; // Initializing postfix as empty string.

for (int i = 0; i < expression.length(); i++)

{

if (expression[i] == ' ' || expression[i] == ',')

continue;

// If character is operator, pop two elements from stack, perform operation and push the result back.

else if (IsOperator(expression[i]))

{

while (!S.empty() && S.top() != '(' && HasHigherPrecedence(S.top(), expression[i]))

{

postfix += S.top();

S.pop();

}

S.push(expression[i]);

}

// Else if character is an operand

else if (IsOperand(expression[i]))

{

postfix += expression[i];

}

else if (expression[i] == '(')

{

S.push(expression[i]);

}

else if (expression[i] == ')')

{

while (!S.empty() && S.top() != '(')

{

postfix += S.top();

S.pop();

}

S.pop();

}

else

{

cout<<"Invalid expression. ";

exit(1);

}

}

while (!S.empty())

{

postfix += S.top();

S.pop();

}

return postfix;

}

bool IsOperand(char C)

{

if (C >= '0' && C <= '9')

return true;

if (C >= 'a' && C <= 'z')

return true;

if (C >= 'A' && C <= 'Z')

return true;

return false;

}

// Function to verify whether a character is operator symbol or not.

bool IsOperator(char C)

{

if (C == '+' || C == '-' || C == '*' || C == '/' || C == '$')

return true;

return false;

}

// Function to verify whether an operator is right associative or not.

int IsRightAssociative(char op)

{

if (op == '$')

return true;

return false;

}

int GetOperatorWeight(char op)

{

int weight = -1;

switch (op)

{

case '+':

case '-':

weight = 1;

case '*':

case '/':

weight = 2;

case '$':

weight = 3;

}

return weight;

}

int HasHigherPrecedence(char op1, char op2)

{

int op1Weight = GetOperatorWeight(op1);

int op2Weight = GetOperatorWeight(op2);

if (op1Weight == op2Weight)

{

if (IsRightAssociative(op1))

return false;

else

return true;

}

return op1Weight > op2Weight ? true : false;

}

int evaluatePostfix(string exp)

{

stack S;

int i;

for (i = 0; exp[i]; ++i)

{

if (isdigit(exp[i]))

S.push(exp[i]-'0');

else

{

int val1 = S.top();

S.pop();

int val2 = S.top();

S.pop();

switch (exp[i])

{

case '+': S.push(val2 + val1); break;

case '-': S.push(val2 - val1); break;

case '*': S.push(val2 * val1); break;

case '/': S.push(val2/val1); break;

}

}

}

return S.top();

}