Extending COALESCE() - Mailing list pgsql-general

Is it possible to extend the COALESCE() function?  I would like to support for coalescing an int into a Boolean, but I get syntax errors if I don’t wrap coalesce in quotes.

CREATE OR REPLACE FUNCTION coalesce(boolean,int) RETURNS boolean AS $$

                SELECT CASE WHEN $1 IS NOT NULL THEN $1 WHEN $2 = 1 THEN true ELSE false END

$$ LANGUAGE sql IMMUTABLE;

Thanks,

Dave