cout/cin not reading or printing

Question

I'm probably not using cin correctly here, but can someone tell me why this small program will not run and produce any output?

#include <iostream>
using namespace std;

class Vector {
public:
   Vector(int s) :elem{new double[s]}, sz{s} {}
  ~Vector() { delete[] elem; } //added this
   double& operator[](int i) { return elem[i]; }
   int size() { return sz; }
private:
   double *elem;
   int sz;
};

double read_and_sum(int s) {
   Vector v(s);
   for (int i=0; i != v.size(); ++i)
      //cin>>v[i];
      v[i]=s;
      cout<<"s = "<<s<<"\n";

   double sum = 0;
      for (int i=0; i != v.size(); ++i)
         sum+=v[i];
   return sum;
}

int main()
{
   int i = 0;
   cout<<"Please enter an integer: ";
   cin >> i;
   cout<<"Sum = "<<read_and_sum(i)<<"\n";
}

Can't reproduce. [Works for me](http://rextester.com/APFMV10845). Are you actually entering 20 double values on standard input? Most likely, the program is waiting for you to type something. — Igor Tandetnik, Jan 18 '16 at 15:11
@Andrew: Hint: Whenever you allocate with `new`, you should also be deallocating later with `delete` (`delete[]`) — AndyG, Jan 18 '16 at 15:13
No. You need a destructor for your Vector class. However this issue has nothing at all to do with cin / cout. — drescherjm, Jan 18 '16 at 15:22
Do you need to pause the console at the end of the program? On some platforms, the console window terminates quickly after the program finishes so people don't think there was any output. — Thomas Matthews, Jan 18 '16 at 15:29
Are you running g++ under Linux? If running with MinGW/Cygwin under Windows [Avast antivirus might be a factor](http://stackoverflow.com/questions/33690697/running-my-c-code-gives-me-a-blank-console). — Bo Persson, Jan 18 '16 at 16:05
Don't you get a error message? I compile it in my Mac, it make a couple of error in constructor. after I fix it, It works. — arubirate, Jan 18 '16 at 16:37
***it make a couple of error in constructor. after I fix it, It works.*** You most likely did not have c++11 enabled. Or do not have a c++11 capable compiler. — drescherjm, Jan 18 '16 at 16:47
I just edited the code to include a destructor in my class but it still doesn't run. It just hangs as soon as I execute `./vector_3`. Any ideas what I'm doing wrong? — Andrew Hummel, Jan 18 '16 at 22:06
***It just hangs as soon as I execute ./vector_3*** Did you type the 20 numbers each separated by a space and hit return? — drescherjm, Jan 19 '16 at 02:33

S A · Answer 1 · 2016-01-18T22:21:35.550

0

The program works perfectly fine. I personally think you are entering the wrong numbers. If you actucally wrote the code, you would know how it works but you say that you're new but I don't think someone that cant understand how someone cant read the code correctly be able to do vectors.

edited Jan 18 '16 at 22:21

answered Jan 18 '16 at 22:19

S A

827
10
23

What do you mean? I'm not entering in any numbers. I hardcoded in 20 when I call read_and_sum from main. – Andrew Hummel Jan 18 '16 at 22:21
1

@Andrew `cin` is used to read from input, so obviously you must input something for the program to run at all – BartoszKP Jan 18 '16 at 22:22
2

@Andrew: I think we found your problem then... You need to be giving your program input! – AndyG Jan 18 '16 at 22:22
@Andrew: I should note that this was mentioned in the very first comment on your question!!! – AndyG Jan 18 '16 at 22:23
@AndyG - ok I changed up read_and_sum function and main. Trying to wrap my head around cin! Thanks for pointing it out! – Andrew Hummel Jan 18 '16 at 22:31

cout/cin not reading or printing

1 Answers1