Extending SQL with a C function

Hi,

how can I write a SQL extention in C, which works with "unusual" data
types?

I've managed to write a c function, which accepts int4 as input parameter
and has got int4 as output parameter.

My problem now is, that I want to use a char(10) as input parameter, since
the input for that function is a colum, which is a char(10) type.
How do I do this?

(In the manuals, it is said, one should create an own data type in C - I've
already done this, called it "char10", but of course, I cannot use this
data type in SQL...)

Thank you very much
  Christoph
-- 
** http://ourworld.compuserve.com/homepages/ChLorenz/ ** ChLorenz@csi.com **
 ** No Spam ! ** No Adverts ! ** No Junk-Mails ! ** No unwanted Mails ! **