Re: boolean states

Kevin Grittner wrote:
> Jack Douglas  wrote:
>
> > There are two kinds of people on this earth, those who understand
> > boolean arithmatic and those who don't. I'm not one of them.
>
> Hmmm...  From that, I don't know if you do.  Which do I record in the
> understands_boolean column of the database record for you?  Dang, I
> knew I should have had *two* flags: known_to_understand_boolean and
> known_to_not_understand_boolean.  That would have been much simpler
> than allowing NULL for UNKNOWN....

Attached patch applied to HEAD and 9.0.X.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
new file mode 100644
index 657835c..c1a34fb
*** a/doc/src/sgml/func.sgml
--- b/doc/src/sgml/func.sgml
***************
*** 82,89 ****
       <member><literal>NOT</></member>
      </simplelist>

!     <acronym>SQL</acronym> uses a three-valued Boolean logic where the null value represents
!     <quote>unknown</quote>.  Observe the following truth tables:

      <informaltable>
       <tgroup cols="4">
--- 82,90 ----
       <member><literal>NOT</></member>
      </simplelist>

!     <acronym>SQL</acronym> uses a three-valued logic system with true,
!     false, and <literal>null</>, which represents <quote>unknown</quote>.
!     Observe the following truth tables:

      <informaltable>
       <tgroup cols="4">