PL/pgsql

I am new to Postgresql and am having problems getting functions working.

I have been following an example in the book "PostgreSQL" by Douglas &
Douglas Published by Developers Library.
I put the  code in as a function (see end of email)


When I execute it from psql I get the following:
dev=# select my_factorial(1);
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.

Can any one help me find the problem.  point me in the right direction?

Thanks
Gene Tuttle




-- Function: public.my_factorial(int4)

-- DROP FUNCTION public.my_factorial(int4);

CREATE OR REPLACE FUNCTION public.my_factorial(int4)
  RETURNS int4 AS
'
  DECLARE
    arg INTEGER;
  BEGIN

    arg := $1;

    IF arg IS NULL or arg < 0 THEN
        RAISE NOTICE \'Invalid Number\';
        RETURN NULL;
    ELSE
        IF arg = 1 THEN
            RETURN 1;
        ELSE
            DECLARE
                next_value INTEGER;
            BEGIN


                next_value := my_factorial(arg - 1) * arg;
                RETURN next_value;
            END;
        END IF;
    END IF;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;