/in/foo.cc: In function 'int main()':
/in/foo.cc:55:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i <= s.size() - 1; i++)
                 ~~^~~~~~~~~~~~~~~
/in/foo.cc:69:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i <= l.size() - 1; i++)
                 ~~^~~~~~~~~~~~~~~
/in/foo.cc:93:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i <= r.size() - 1; i++)
                 ~~^~~~~~~~~~~~~~~
/in/foo.cc:121:8: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%c=%.3lf", ch, root);
  ~~~~~~^~~~~~~~~~~~~~~~~~~~~~