//Downloaded From -- Programmers Inn - http://akbani.20m.com

/*
Name: Asdaq Amin
Email: asdaqamin@hotmail.com
Language: C\C++
Category: Data Structures
Description: This prgram takes the Postfix Arithmatic expression and
give the result to a single constant value.For this purpose we used
stack implementation.
*/

//Asdaq Amin
// Bahria University ISl(Pak)
// Assignment of Data Structure

#include <conio.h>
#include <iostream.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

const int MAX=20;

class Postfix{
private:
int Opndstk[MAX]; //Operator
int top;
public:
Postfix()
{ top=-1;}
void push(int);
int pop();
void Evalute(char);
void display();
};
void Postfix::push(int Op)
{ if(top<MAX-1)
{ Opndstk[++top]=Op;

}
}
int Postfix::pop()
{
if(top>-1)
{ return Opndstk[top--];}
}
void Postfix::Evalute(char OPR)
{
int Opnd1,Opnd2;
Opnd2=pop();
Opnd1=pop();
if(OPR=='+')
{
push(Opnd1+Opnd2);
}
else if(OPR=='-')
{
push(Opnd1-Opnd2);
}
else if(OPR=='/')
{
push(Opnd1/Opnd2);
}
else if(OPR=='*')
{
push(Opnd1*Opnd2);
}
else if(OPR=='$')
{
push(pow(Opnd1,Opnd2));
}

}
void Postfix::display()
{ cout << "The value of Postfix expression is="<<Opndstk[top];
}
void main()
{
Postfix P1;
clrscr();
int len,Opnd; //calculate String length
char STR[MAX];
cout << "Enter the Expression in Postfix ";
gets(STR);
len=strlen(STR);
for(int i=0;i<len;i++)
{ if(int(STR[i])>47 && int(STR[i])<58)
{ Opnd=int(STR[i])-48;
P1.push(Opnd);
}
else if((STR[i]=='+')||(STR[i]=='-')||(STR[i]=='/')||(STR[i]=='*')||(STR[i]=='$'))
{
P1.Evalute(STR[i]);
}
}
P1.display();
getche();
}