foo.cc: In function ‘int main()’:
foo.cc:9:13: error: ‘i’ was not declared in this scope
    9 |         for(i=0,i<n,i++)
      |             ^
foo.cc:12:13: error: expected primary-expression before ‘else’
   12 |             else
      |             ^~~~
foo.cc:11:33: error: expected ‘;’ before ‘else’
   11 |                         cout<<1;
      |                                 ^
      |                                 ;
   12 |             else
      |             ~~~~                 
foo.cc:12:13: error: expected primary-expression before ‘else’
   12 |             else
      |             ^~~~
foo.cc:11:33: error: expected ‘)’ before ‘else’
   11 |                         cout<<1;
      |                                 ^
      |                                 )
   12 |             else
      |             ~~~~                 
foo.cc:9:12: note: to match this ‘(’
    9 |         for(i=0,i<n,i++)
      |            ^
foo.cc:12:13: error: expected primary-expression before ‘else’
   12 |             else
      |             ^~~~
foo.cc:7:13: warning: unused variable ‘a’ [-Wunused-variable]
    7 |         int a=1,b=1;
      |             ^
foo.cc:7:17: warning: unused variable ‘b’ [-Wunused-variable]
    7 |         int a=1,b=1;
      |                 ^