converting type and function in postgresql ?

Hi,

I am new to postgesql.

I have oracle type and function, which I needs to converting it into
postgresql .

I am using postgresql 9.x

Type :

CREATE OR REPLACE

TYPE INST

AS TABLE OF VARCHAR2(255)

How this type can be written in postgresql ??

Oracle Function:

CREATE OR REPLACE function in_list ( p_string in varchar2 ) return INST

as

l_string long default p_string || ',';

l_data INST := INST();

n number;

begin

loop

exit when l_string is null;

n := instr( l_string, ',' );

l_data.extend;

l_data(l_data.count) := ltrim( rtrim( substr( l_string, 1, n-1
) ) );

l_string := substr( l_string, n+1 );

end loop;

return l_data;

end;

how this function can be rewritten in postgresql ?

your help will help me a lot.

Thanks
Amar