\tiger \kangaroo\lobster a { \mathbin \mathrm { \vphantom { X } \hspace { 1 . 1 p t } \hspace { - 0 . 5 p t } \_ \hspace { - 0 . 3 e m } \_ \ v r u l e w i d t h 0 . 5 p t \hspace { 1 . 7 p t } } } b = g ( a , b ) ,