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Date:         Tue, 21 Nov 1995 21:37:23 -0500
Reply-To: Jorge Llambias <jorge@PHYAST.PITT.EDU>
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From: Jorge Llambias <jorge@PHYAST.PITT.EDU>
Subject:      Re: Colourless green ideas
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To: John Cowan <cowan@LOCKE.CCIL.ORG>
Status: OR
X-From-Space-Date: Tue Nov 21 21:46:45 1995
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la dilyn cusku di'e

> But I'm not sure I really understand And's argument.  I'd like to see some
> explicit examples of meaningless statements using PA.

Any statement involving {li pipaipi} for example.

> I'd also like to
> see a proposal for the substructure of PA, preferably one that doesn't
> rule out any current texts.

This is not a full proposal, but I posted this in March:

The parser accepts any string of PAs as a number, but not all
combinations are meaningful (at least to me). Here is an attempt
to describe which are the meaningful combinations, written in
bnf-ish notation. (I believe this mostly agrees with the grammar
paper, with the exception of my treatment of {ji'i}.)

(The parser also accepts letterals as parts of numbers. I've
ignored them here.)


<digit> = no|pa|re|ci|vo|mu|xa|ze|bi|so|dau|fei|gai|jau|rei|vai|ki'o

<natural> = <digit> ... | xo | no'o

<sign> = (su'o|su'e|me'i|za'u) & (ma'u|ni'u)

<real0> = <natural> & (pi [<natural>] & (ra'e <natural>)) | pai | te'o | ci'i

<real> = <sign> & <real0> & (ji'i <real0>)

<complex> = <real> & (ka'o <real>)

<fraction> = <complex> & (fi'u <complex>)

<quantifier0> = (su'o|su'e|me'i|za'u|da'a) &
                (ro|so'a|so'e|so'i|so'o|so'u|rau|mo'a|du'e|ci'i|<natural>)

<quantifier> = <quantifier0> ...

<fractionator> = pi <quantifier>

<percentage> = (<real> | <quantifier>) ce'i

<general> = <fraction>|<quantifier>|<fractionator>|<percentage>|tu'o

<number> = <general> & (pi'e [<general>]) ...


Notes:

1- {ki'o} is a special digit. There has to be a number of digits
   multiple of three between {ki'o}s or between {ki'o} and {pi}.
   If there aren't three explicit digits then 0s are assumed
   implicitly as the higher order digits.
   If ki'o is the first digit, a 1 is assumed in front.
   e.g.  ki'ore = 1002  ; piciki'o = 0.003

2- Either {fi'u} or {ka'o} has to have higher scope than the other,
   otherwise {1fi'u2ka'o3} would be ambiguous between .5+3i and
   1/(2+3i).
   I prefer to give fi'u higher scope, because that allows
   {fi'u <complex>} to be the inverse of <complex>. The other
   possibility would not allow an easy way to express inverses,
   and things like "2/3 + i4/5" are not really as important as
   inverses.

3- My interpretation of {ji'i} allows to say everything that you can
   say with the one proposed in the grammar paper, and more.
   With my interpretation <number>ji'i<number> means a number
   between those two, or approximately that. So 20ji'i30 would
   be a number between 20 and 30, but could eventually be 19 or 31,
   it is approximate, and the difference between the numbers gives
   an idea of the uncertainty.

   With the interpretation of the paper, 20ji'i30 would be a number
   between 2010 and 2099, or something like that. To say that with
   my interpretation, I would say 2050ji'i or ji'i2050. The
   uncertainty is given by the last significant (non-zero) digit.
   {ji'i} would only say that the total number is not exact, not
   a particular digit. (The ji'i+ and ji'i- convention for rounding
   still works.)


Comments about all this are most welcome and solicited.

Jorge