infix operation to postfix using stacks
- by Chris De La O
We are writing a program that needs to convert an infix operation (4 5/3) to postfix (4 5 3 / ) using stacks. however my convert to postfix does not work as it doesnt not output the postFix array that is supposed to store the conversion from infix notation to postfix notation. here is the code for the convertToPostix fuction.
//converts infix expression to postfix expression
void ArithmeticExpression::convertToPostfix(char *const inFix, char *const postFix)
{
//create a stack2 object named cow
Stack2<char> cow;
cout<<postFix;
char thing = '(';
//push a left parenthesis onto the stack
cow.push(thing);
//append a right parenthesis to the end of inFix array
strcat(inFix, ")");
int i = 0;//declare an int that will control posFix position
//if the stack is not empty
if (!cow.isEmpty())
{
//loop to run until the last character in inFix array
for (int x = 0; inFix[x]!= '\0'; x++ )
{
//if the inFix element is a digit
if (isdigit(inFix[x]))
{
postFix[i]=inFix[x];//it is assigned to the next element in postFix array
i++;//move on to next element in postFix
}
//if the inFix element is a left parenthesis
else if (inFix[x]=='(')
{
cow.push(inFix[x]);//push it unto the stack
}
//if the inFix element is an operator
else if (isOperator(inFix[x]))
{
char oper2 = inFix[x];//char variable holds inFix operator
if (isOperator(cow.stackTop()))//if the top node in the stack is an operator
{
while (isOperator(cow.stackTop()))//and while the top node in the stack is an operator
{
char oper1 = cow.stackTop();//char variable holds node operator
if(precedence( oper1, oper2))//if the node operator has higher presedence than node operator
{
postFix[i] = cow.pop();//we pop such operator and insert it in postFix array's next element
cow.push(inFix[x]);//and push inFix operator unto the stack
i++;//move to the next element in posFix
}
}
}
//if the top node is not an operator
//we push the current inFix operator unto the top of the stack
else
cow.push(inFix[x]);
}
//if the inFix element is a right parenthesis
else if (inFix[x]==')')
{
//we pop everything in the stack and insert it in postFix
//until we arrive at a left paranthesis
while (cow.stackTop()!='(')
{
postFix[i] = cow.pop();
i++;
}
//we then pop and discard left parenthesis
cow.pop();
}
}
postFix[i]='\0';
//print !!postFix array!! (not stack)
print();//code for this is just cout<<postFix;
}
