/in/foo.c:4:1: error: unknown type name 'bool'
    4 | bool is_prime(int n) {
      | ^~~~
/in/foo.c: In function 'is_prime':
/in/foo.c:5:24: error: 'false' undeclared (first use in this function); did you mean 'fclose'?
    5 |     if (n <= 1) return false;
      |                        ^~~~~
      |                        fclose
/in/foo.c:5:24: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:24: error: 'true' undeclared (first use in this function)
    6 |     if (n == 2) return true;
      |                        ^~~~
/in/foo.c: In function 'main':
/in/foo.c:16:12: error: 'cin' undeclared (first use in this function)
   16 |     while (cin >> M && M != 0) {
      |            ^~~
/in/foo.c:21:17: error: 'cout' undeclared (first use in this function)
   21 |                 cout << i << " " << j << endl;
      |                 ^~~~
/in/foo.c:21:42: error: 'endl' undeclared (first use in this function)
   21 |                 cout << i << " " << j << endl;
      |                                          ^~~~
/in/foo.c: In function 'is_prime':
/in/foo.c:12:1: warning: control reaches end of non-void function [-Wreturn-type]
   12 | }
      | ^