Can't convert numeric to_char() in catenate function

Hi there.

Im trying to do the usual row catenation function, but for a "numeric" type column.  I have this:

CREATE OR REPLACE FUNCTION "verticat" (text, numeric) RETURNS text AS '
SELECT CASE WHEN $2 IS NULL THEN $1           WHEN $1 IS NULL OR $1 = ''''     THEN to_char($2,'999999999D99')
ELSE $1 || '', '' || to_char($2,'99999999D99')      END
 
' LANGUAGE 'sql';

This works without problem with "float" or other type with direct casting to text (after replacing the "to_char(...)"
with$2::text), but this one gives me an "ERROR:  parser: parse error at or near "999999999""... wath is wrong with
it??

It would also be nice to trim the spaces placed by to_char, with something like "ltrim(' ',
to_char($2,'999999999D99'))",but that yields yet anoter error:  "ERROR:  parser: parse error at or near "'"".
 

Any help 'preciated.  Thanks!