flip              105 src/Monotonic.cpp         result = unify(ra, flip(rb));
flip              121 src/Monotonic.cpp             result = flip(rb);
flip              123 src/Monotonic.cpp             result = flip(ra);
flip              141 src/Monotonic.cpp             result = flip(ra);
flip              192 src/Monotonic.cpp         result = unify(flip(ra), rb);
flip              229 src/Monotonic.cpp         result = flip(result);