Conver bool to text

Is there a way to convert a boolean value to text and/or vice versa?

You can
select 'true'::boolean,
which *seems* to convert a text string to boolean, but
select 'true'::text::boolean
earns the message
ERROR: cannot cast type text to boolean

You can't go the other way either
SELECT true::text
ERROR: cannot cast type boolean to text

and to_char() doesn't know about booleans.

It's not that difficult to write a fuction to convert boolean to text,
but I'm wondering if there's already something that does this?

--
Edmund Bacon <ebacon(at)onesystem(dot)com>