c++ - Object initialized with random numbers -

i'm pretty new c++ , oo, pretty silly. in code right after include statements.

enum objtype { cube, cone, }; typedef struct {    objtype type;    float x;    float y;    float z;    int selected; } object;  static object objects[] = {      { cube, rand()%11-4, rand()%-10-5, rand()%-65-55, 0},     { cone, rand()%11-4, rand()%-10-5, rand()%-65-55, 0}, } 

i make call srand, passing in current time, in main method. however, generating same random numbers every time program wrong. not understanding?

as zenith says, initialization of globals happens before main(). srand() run first doing declaring global variable initialization calls srand(), , comes before initialization of static object objects[]:

static int x = (srand(time(null)), 10);  static object objects[] = {      { cube, rand()%11-4, rand()%-10-5, rand()%-65-55, 0},     { cone, rand()%11-4, rand()%-10-5, rand()%-65-55, 0}, }; 

but global variables bad idea anyway, , relying on things initialization order (which specified between objects initialized in same translation unit) particularly bad.

instead use local variables:

int main() {   srand(time(null));    object objects[] =   {      { cube, rand()%11-4, rand()%-10-5, rand()%-65-55, 0},     { cone, rand()%11-4, rand()%-10-5, rand()%-65-55, 0},   };    // pass objects around needed   foo(objects[0]);   foo(objects[1]); } 

---

the c++ standard library provides facilities superior srand(), rand(), , manually transforming results generate particular distributions. use header <random>, create , seed generator such std::mt19937 using random_device instead of time(null), , use distribution objects:

#include <random>  int main() {   std::random_device r;   std::seed_seq seed{r(), r(), r(), r(), r(), r(), r(), r()};   std::mt19937 eng(seed);    std::uniform_int_distribution<> dist;   object objects[] =   {      { cube, dist(eng, {-4, 6}), dist(eng, {-5, 4}), dist(eng, {-55, 9}), 0},     { cone, dist(eng, {-4, 6}), dist(eng, {-5, 4}), dist(eng, {-55, 9}), 0},   };    // pass objects around needed   foo(objects[0]);   foo(objects[1]); } 

note how easier read, right down directly stating desired intervals, rather relying on how % behaves negative numbers.

(i'm not sure original intervals weren't mistakes, i've faithfully reproduced them assuming common behavior % negative numbers, wasn't standardized until c++11.)