Oracle Inversion inversion function

Oracle provides a inverted inverted function reverse, but this function cannot be grouped upside down, this article provides a function that can be grouped upside down, as follows:

CREATE OR REPLACE FUNCTION reverse_f (p_str VARCHAR2, P_delimiter varchar2:= ")  RETURN VARCHAR2 is  V_return VARCHAR2 (4000);  VP_STR   VARCHAR2 (4000): = P_STR;  V_IDX number    ;  Vp_len number   : = Length (P_delimiter); BEGIN  if (P_delimiter is null) then    Select Reverse (p_str) to V_return from dual;  else    loop      v_idx: = InStr (Vp_str, p_delimiter);      if (v_idx = 0) Then        v_return: = Vp_str | | v_return;        Exit;      elsif (v_idx = 1) then        v_return: = substr (Vp_str, 1, vp_len) | | V_return;        Vp_str   : = substr (Vp_str, Vp_len + 1);      else        V_return: = substr (Vp_str, 1, v_idx-1) | | V_return;        Vp_str   : = substr (Vp_str, v_idx);      End If;    End Loop;  End If;  RETURN V_return; END Reverse_f;

Oracle Inversion inversion function