what is the error in my program?

Question

#ifndef UNIFORM_H
#define UNIFORM_H

double unif();
double unif(double a, double b);
long unif(long a);
void seed();

#endif // UNIFORM_H

#include "uniform.h"
#include <cstdlib>
#include <ctime>
#include <cmath>
using namespace std;
double unif()
{
    return rand() / double(RAND_MAX);
}

 double unif(double a, double b)
  {
     return (b-a)*unif() + a;
  }
long unif(long a)
 {
   if (a < 0) a = -a;
   if (a==0) return 0;
   return long(unif()*a) + 1;
}
 void seed()
 {
     srand(time(0));
 }

Answer 1

I don't see any problem with the shared code. Unless that's all of your code. You need to have a main() function in your code: that's the entry point of the program.

uniform.h

#ifndef UNIFORM_H
#define UNIFORM_H

double unif();
double unif(double a, double b);
long unif(long a);
void seed();

#endif // UNIFORM_H

uniform.cpp

#include <cmath>
#include <cstdlib>
#include <ctime>

#include "uniform.h"

using namespace std;

double unif()
{
    return rand() / double(RAND_MAX);
}

double unif(double a, double b)
{
    return (b-a)*unif() + a;
}

long unif(long a)
{
    if (a < 0) a = -a;
    if (a==0) return 0;
    return long(unif()*a) + 1;
}

void seed()
{
    srand(time(0));
}

main.cpp

#include <iostream>

#include "uniform.h"

int main()
{
    seed();
    for (int i = 0; i < 10; i++)
        std::cout << unif() << std::endl;
    return 0;
}