newbie in C here. I'm trying to have a different value for a variable everytime I run a program. I have this code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define ADD 1
#define SUB 2
#define MUL 3
#define DIV 4
int main(void)
{
double out;
int choice;
float x, y;
printf("Welcome to our first calculator program!\n");
printf("===========================\n");
printf("Please insert 2 numbers:\n");
scanf("%f%f", &x, &y);
choice = 1 + srand(time(NULL)) % 4;
if(choice == ADD)
out = x + y;
else if(choice == SUB)
out = x - y;
else if(choice == MUL)
out = x * y;
else
{
if(y != 0)
out = x / y;
else
{
out = 0;
fprintf(stderr, "error");
return 1;
}
}
printf("The outcome is: %0.2lf\n", out);
return 0;
}
but it always gives me 4 in choice. I don't get why...
Can you help me? Thanks.
Right now you are calling srand and expecting a random number. You should seed the entropy pool by calling srand and THEN calling rand to get the random number :)
An example of usage taken from: http://www.cplusplus.com/reference/cstdlib/srand/
int main ()
{
printf ("First number: %d\n", rand()%100);
srand (time(NULL));
printf ("Random number: %d\n", rand()%100);
srand (1);
printf ("Again the first number: %d\n", rand()%100);
return 0;
}
See how you seed by calling srand and then retrieve the random integer from rand
You need to do this:
srand(time(NULL));
choice = 1 + rand() % 4;
instead of this:
choice = 1 + srand(time(NULL)) % 4;
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