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/*…PROGRAM
FOR EVALUATION OF PREFIX
EXPRESION
SUING STACK AND SELF REFERENTIAL CALSSES..*/
#include<iostream.h>
#include<math.h>
#include<ctype.h>
#include<string.h>
//DECLARATION
OF THE SELFREFEENTIAL CLASSES
class
prefix
{
int data;
prefix *next;
public:
//MEMBER FUCTIONS
DECLARATION
void evaluate(char []);
void push(int );
int pop();
void show();
}*top;
/*FUNCTION
FOR EVALUATION OF PREFIX EXPRESION*/
void
prefix::evaluate(char *exp)
{
int
res;
for(int
i=0;exp[i]!=”;i++)
{
if(isdigit(exp[i]))
{
int item=exp[i]-’0′;
push(item);
}
else
{
int n1,n2;
n1=pop();
n2=pop();
switch(exp[i])
{
case ‘+’:
res=n1+n2;
break;
case ‘-’:
res=n2-n1;
break;
case ‘*’:
res=n2*n1;
break;
case ‘$’:
res=pow(n2,n1);
break;
case ‘/’:
res=n2/n1;
break;
default:
cout<<”ENTER
CORRECT EXPRESION”;
}
push(res);
}
}
}
//FUNCTION
FOR PUSHING DIGITS
void
prefix::push(int ele)
{
prefix *n,*temp;
n=new(prefix);
n->data=ele;
n->next=NULL;
temp=top;
if(top==NULL)
top=n;
else
{
temp=top;
n->next=temp;
top=n;
}
}
//FUNCTION
FOR POPPING DIGITS
int
prefix::pop()
{
int t;
prefix *temp;
if(top==NULL)
cout<<”LIST
IS EMPTY:”;
else
{
temp=top;
t=top->data;
top=temp->next;
delete temp;
}
return(t);
}
//FUNCTION
FOR SHOWING OUTPUT
void
prefix::show()
{
int m=pop();
cout<<”AFTER
EVALUATION THE
VALUE OF THE EXPRESION ->”;
cout<<m;
}
void
main()//MAIN()
FUNCTION STARTS
{
char x[22],*z;
top=NULL;
prefix
p;//OBJECT
CREATION
cout<<”ENTER THE PREFIX EXPRESION”;
cin>>x;
z=strrev(x);//REVERSING OF THE
STRING
p.evaluate(z);
p.show();
}//END OF MAIN()
//END
OF PROGRAM
/*OUTPUT:
ENTER
THE PREFIX EXPRESION+1*23
AFTER
EVALUATION THE
VALUE OF THE EXPRESION ->7
Press
any key to continue
ENTER
THE PREFIX EXPRESION+2-$24*52
AFTER
EVALUATION THE VALUE
OF THE EXPRESION ->-4
Press any key to
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