Getting the same number even after using srand function.

[DanielSteel124]

Hi. So I was trying to create a very simple code where it would randomly generate 10 different values. But despite using the srand function I'm still getting the same input over and over again.
Here's the code:

#include <iostream>
#include <time.h>
using namespace std;

int main()
{
	int srand(time(NULL));	
	int i = rand() % 10 + 1;

	for (int counter = 0; counter < 10; counter = counter++)
	{
		cout << i << endl;
	}

	return 0;

}

[JLBorges]

#include <iostream>
// #include <time.h>
#include <ctime>
// using namespace std;

int main()
{
        // int srand(time(NULL));	// *** create an integer called srand
	std::srand( std::time(nullptr) ); // call the function std::srand
	// int i = rand() % 10 + 1;

	for (int counter = 0; counter < 10; ++counter )
	{
	    // generate a new pseudo random number each time through the loop (?)
	    const int i = rand() % 10 + 1;
	    std::cout << i << '\n' ; // endl;
	}

	// return 0; // there is an implicit return 0 at end of main
}

[George P]

Generating random numbers using the C++ <random> library:

#include <iostream>
#include <random>
// http://www.cplusplus.com/reference/random/

int main()
{
   // let's create a C++ random engine and seed it
   std::default_random_engine rng(std::random_device {}());

   // let's create a distribution that generates random numbers between 1 - 10 inclusive
   std::uniform_int_distribution<int> dis(1, 10);

   for (int i { }; i < 10; ++i)
   {
      std::cout << dis(rng) << ' ';
   }
   std::cout << '\n';
}

This isn't the only way to generate random numbers in C++, <random> has quite a number of facilities available. Including generating floating point numbers.

[George P]

https://www.learncpp.com/cpp-tutorial/random-number-generation/

[dhayden]

The reason you must put rand() % 10 + 1 inside the for loop is because C++ doesn't work like Excel. Excel let's you assign a formula to a cell and updates the value as needed based on the formula. In C++, the program evaluates the expression when encountered and assigns the resulting value to the variable. The value of the variable doesn't change until you assign something else to it.