Found within interface IGround.

FIFTH  FOURTHFIFTH

FIRSTFIFTH  FIRSTFOURTHFIFTH

SECONDFIFTH  SECONDFOURTHFIFTH

FIRSTSECONDFIFTH  FIRSTSECONDFOURTHFIFTH

THIRDFIFTH  THIRDFOURTHFIFTH

FIRSTTHIRDFIFTH  FIRSTTHIRDFOURTHFIFTH

SECONDTHIRDFIFTH  SECONDTHIRDFOURTHFIFTH

FIRSTSECONDTHIRDFIFTH   FIRSTSECONDTHIRDFOURTHFIFTH

All of these grounds define a bit vector which describes a ground argument by 1 and a variable by 0. Instead of these names an appropriate bit vector can be used. The vector is read from right to left; its last bit describes the first argument.