Passing regular expression backreference to SQL function

Question

Does anyone know if it is possible to pass a regular expression backreference to an SQL function?
When I try this:
SELECT REGEXP_REPLACE('/abc/23468/xyz1/10/', '(/)([[:digit:]]+)', '\1'||LENGTH('\2')) FROM dual;
I am getting this back:
/abc/2/xyz1/2/
Here LENGTH function takes backreference '\2' literally as a string and does not replace it with the actual value.
Hence, it always returns length of 2 instead of the correct value.
However, if do this
SELECT REGEXP_REPLACE('/abc/23468/xyz1/10/', '(/)([[:digit:]]+)', '\1'||SUBSTR('\2',0)) FROM dual;
I get the right result back
/abc/23468/xyz1/10/
So, SUBSTR works correctly.
Why do LENGTH and SUBSTR handle backreference diffrently?
I am using Oracle 10.2.
Appreciate any help on this.

Answer 1

How about this?
CREATE OR REPLACE FUNCTION fmt_string(
  p_Source IN VARCHAR2,
  P_Delim  IN VARCHAR2 DEFAULT '/'
) RETURN VARCHAR2
IS
  v_Start  PLS_INTEGER;
  v_Pos    PLS_INTEGER;
  v_Len    PLS_INTEGER;
  v_String VARCHAR2(4000);
  v_Result VARCHAR2(4000);
BEGIN
  v_Len   := LENGTH(p_Source);
  v_Start := 1;
  WHILE v_Start <= LENGTH(p_Source)
  LOOP
    v_Pos := INSTR(p_Source, p_Delim, v_Start);
    IF v_Pos = 0 THEN
       v_Pos := v_Len;
    END IF;
    v_String := SUBSTR(p_Source, v_Start, v_Pos - v_Start);
    IF REGEXP_LIKE(v_String, '^[0-9]+$') THEN
       v_String := TO_CHAR(TO_NUMBER(v_String), 'fm0000000000');
    END IF;
    v_Result := v_Result || v_string || p_Delim;
    v_Start  := v_Pos + 1;
  END LOOP;
  RETURN v_Result;
END fmt_string;
/using it this way:
SELECT fmt_string('/abc/23468/xyz1/10/')
  FROM dual;You could put that function also into a PACKAGE.
C.