Re: Converting varchar to bool

On Wed, Jun 15, 2005 at 14:14:46 +0200,
KÖPFERL Robert <robert(dot)koepferl(at)sonorys(dot)at> wrote:
> Hi,
>
>
> I have currently trouble working with boolean values and variables in
> functions.
>
> As one would expect, a
> select '1'::bool, 't'::bool, 'true'::unknown::boolean
>
> works.
>
> As a select '1' tells us this seems as a conversion unknown->bool
> or ??maybe?? a boolean literal??

No it is not a conversion, '1', 't' and 'true' are all valid boolean
strings representing TRUE. The input is not being converted from text
to boolean.

>
> what-o-ever, at least my function gets not accepted:
>
>
> CREATE OR REPLACE FUNCTION testbool(varchar)
> RETURNS boolean AS
> $BODY$
> SELECT $1::boolean
> $BODY$
> LANGUAGE 'sql' STABLE STRICT SECURITY DEFINER;
>
> Postgres complains that it can't convert varchar to boolean.
> Actually neither $1::unknown::bool works.
> It turns out that there exists no conversion varchar/text/unknown ->
> boolean.
> Actually there's not any conversion -> boolean.
>
> How should this be treaten?
> *being confused*
>
>
> sorry for duplicating (I'm sure) this topic, at least I tried to find it in
> the listarcive.

It has been discussed in the last week.

test.sql:
CREATE OR REPLACE FUNCTION testbool(varchar)
RETURNS boolean AS
$BODY$
SELECT boolin(textout($1));
$BODY$
LANGUAGE 'sql' STABLE STRICT SECURITY DEFINER;

SELECT testbool('true');

bruno=> \i test.sql
CREATE FUNCTION
testbool
----------
t
(1 row)