CREATE TYPE with array

Hi folks,

I tried to create a new type with an array in it.  So I took an example
from (the german translation of) "PostgreSQL: Introduction and Concepts"
by Bruce Momjian.

This example says:

create type int4array (
       input=array_in,output=array_out,
       internallength=variable,element=int4
);


Now, psql complains:

ERROR:  TypeCreate: function array_out(int4array) does not exist

I'm using PostgreSQL 7.3.2 (came with SuSE Linux 8.1).
Have things changed, or did I overlook something?

If I ask psql

\df array

array_out (among others) appears in the list of functions.
Myfirst guess is that array_{in,out} is somehow predefined, so that I
have not to define functions by hand - or is this wrong?

Thanks!
    Wolfgang