-- | extracts the predicate name from the predicate symbol
pred_symb_name :: PRED_SYMB -> PRED_NAME
pred_symb_name (Pred_name pn) = pn
pred_symb_name :: PRED_SYMB -> PRED_NAME
pred_symb_name (Pred_name pn) = pn
pred_symb_name (Pred_name pn) = pn