Answer to Question #29591 in C++ for mostafavalipour

Question #29591
#include <iostream>
#include <string>
#include <sstream>
using namespace std;

bool die(const string &msg);

//stack class
class Stack{
void push(const double &val);
void push(const string &oper);
double popnum();
string popop();
double getopele();
double getnumele();
static const unsigned MAX=30;
string opstack[MAX];
double numstack[MAX];
unsigned opele;
unsigned numele;

//operator type
struct OP{
string name;
void * func;
unsigned arity;
unsigned prec;
bool lass;
string descrip;
//operator table
OP op[]={{"+", add, 2, 4, true, "2+3 is 5"},
{"-", subtract, 2, 4, true, "2-3 is -1"},
{"*", multiply, 2, 6, true, "2*3 is 6"},
{"/", divide, 2, 6, true, "2/3 is 0.666666..., div by 0 illegal"}};
unsigned OPELE =sizeof(op)/sizeof(op[0]);

bool add(double &r, double &x, double &y);
bool subtract(double &r, double &x, double &y);
bool multiply(double &r, double &x, double &y);
bool divide(double &r, double &x, double &y);

unsigned findindex(string token, OP op[], unsigned OPELE);
bool parse(double &t, const string &token);
bool evaluate(double &result, string line);
bool weird(double x);

int main(){
for(string line; getline(cin, line);){
if(line=="QUIT") break;
if(line.empty()) continue;
for(unsigned i=0; i<OPELE; i++)
cout<<op[i].name<<" | "<<op[i].descrip<<'\n';
double result;
if(evaluate(result, line)){
cout<<"Could not understand input\n\n";


void Stack::push(const double &val){
if(MAX) die("Stack Overflow");

void Stack::push(const string &oper){
if(MAX) die("Stack Overflow");

double Stack::popnum(){
if(!numele) die("Stack Underflow");
return numstack[--numele];

string Stack::popop(){
if(!opele) die("Stack Underflow");
return opstack[--opele];

double Stack::getopele(){
return opele;

double Stack::getnumele(){
return numele;

bool add(double &r, double &x, double &y){
double t = x + y;
if( weird(t) ) return false;
r = t;
return true;

bool subtract(double &r, double &x, double &y){
double t = x - y;
if( weird(t) ) return false;
result = t;
return true;

bool multiply( double & r, double& x, double &y ){
double t = x * y;
if( weird(t) ) return false;
result = t;
return true;

bool divide( double & result, double &x, double &y ){
double t = x / y;
if( weird(t) ) return false;
result = t;
return true;

unsigned findindex(string token, OP op[], unsigned OPELE){
for(unsigned i=0l i<OPELE; i++)
return i;
return UINT_MAX;


bool parse(double &t, const string &token){
istringstream sin( token );
double t;
if( !(sin >>t) ) return false;
char junk;
if( sin >>junk ) return false;
value = t;
return true;

bool evaluate(double &result, string line){
istringstream sin(line);
Stack s;
for(string token; sin>>token;){
double t;
if(parse(t, token)){
}else if(

bool weird( double x ){
return x != x || x != 0 && x == 2*x;
Expert's answer
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01.05.13, 15:26

Sir its a simple program (printf and scanf )statement but I didnot understand please help me Q:A computer Company produce 3291 computers in 2010. Its priduction increases by 12%.In how many years will production exceed 8000 computers per years?

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