/in/foo.c: In function 'main':
/in/foo.c:7:7: warning: statement with no effect [-Wunused-value]
  for(i==2;i<n;i++)
      ~^~~
/in/foo.c:14:12: warning: format '%d' expects a matching 'int' argument [-Wformat=]
   printf("%d is a primer!");
            ^
/in/foo.c:16:12: warning: format '%d' expects a matching 'int' argument [-Wformat=]
   printf("%d is not a primer!");
            ^
/in/foo.c:9:7: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if(n%i==0)
      ~^~