To_number default format

Question

My question is actually related to my answer to Trigger for changing decimal symbol (comma to point)
What is the default format for to_number? The default format for to_char(number) is TM9, but I cannot figure out the default format for to_number.
Ok, here is my puzzle :
SQL> alter session set nls_numeric_characters=',.';
SQL> select STRING, to_number(string) from x;
STRING          TO_NUMBER(STRING)
-0,000000000001        -1,000E-12
999999999999999        1,0000E+15
1e+25                  1,0000E+25try to do this without alter session but with to_number(string,<fmt>,'nls_numeric_characters='',.''');
An ice-cream for the first to find out the right fmt :-)
Regards
Laurent

Answer 1

roll your own NLS-converter :
col value format 9.9999999999999EEEE
select string, to_number(translate(string  , ',.' , '.' )) value
  from (      select '-0,000000000001'    string from dual
        union select '999999999999999'    string from dual
        union select '1E+25'              string from dual
        union select '123.456.789,012345' string from dual
       ) A
STRING                               VALUE
-0,000000000001       -1.0000000000000E-12
123.456.789,012345     1.2345678901235E+08
1E+25                  1.0000000000000E+25
999999999999999        1.0000000000000E+15
  didn't find any other way out so far