[lojban-beginners] Re: "djuno najo cusku"

[David Gowers <00ai99@gmail.com>]

On Thu, Jun 18, 2009 at 12:28 PM, Minimiscience <minimiscience@gmail.com> wrote:
> .skamyxatra
>
> "{najo}" and "{jonai}" are essentially the same thing; "(NOT p) IFF q" is
> logically equivalent to "p IFF (NOT q)", which are both equivalent to "p XOR
> q."

so P najo Q == (NOT p) IFF q?

>
> > of course you could also do the excessively verbose
> > "djuno najo cusku .e cusku najo djuno" to express the idea.
>
> Two things:
>
> 1. The logical connectives for a given type of connection ({sumti}, {tanru},
>   etc.) all have the same precedence and are left-associative.  Thus, that
>   utterance corresponds to "((djuno XOR cusku) AND cusku) XOR djuno)", which
>   happens to simplify to "djuno OR cusku," i.e., "{djuno ja cusku}."  To get
>   around this, either attach "{bo}" to each "{najo}" (technically, only the
>   second one needs it, but attaching to both is better for symmetry), or put a
>   "{ke}" after the "{.e}."
>
> 2. You're mixing a {tanru} connective ("{najo}") with a {sumti} connective
>   ("{.e}") inside a {tanru}.  Either change the "{.e}" to "{je}" or otherwise
>   reword the utterance (e.g., something like "{lonu djuno najo cusku .e lonu
>   cusku najo djuno}").

Ah thanks, minimiscience. It looks like I just didn't understand IFF
correctly. The truth table in
http://en.wikipedia.org/wiki/If_and_only_if has helped there.
So, 'djuno najo cusku' means 'not-know IFF say' ie the truth value for
P is inverted so the truth table looks like

P(djuno) Q(cusku) [P iff Q]
F T T
F F F
T T F
T F T

Which is indeed XOR. Thanks!

David