/in/foo.cc: In function 'int main()':
/in/foo.cc:32:12: warning: unused variable 'r' [-Wunused-variable]
     double r = 100.0, l = -100.0, m;
            ^
/in/foo.cc:32:23: warning: unused variable 'l' [-Wunused-variable]
     double r = 100.0, l = -100.0, m;
                       ^
/in/foo.cc:32:35: warning: unused variable 'm' [-Wunused-variable]
     double r = 100.0, l = -100.0, m;
                                   ^