foo.cc: In function ‘int main()’:
foo.cc:10:14: error: expected primary-expression before ‘int’
   10 |         f1or(int i=0;i<n;i++)
      |              ^~~
foo.cc:10:22: error: ‘i’ was not declared in this scope
   10 |         f1or(int i=0;i<n;i++)
      |                      ^