[lojban] Re: A completely different RPN solution.

[Jim Carter <jimc@math.ucla.edu>]

On Sat, 7 Feb 2009, Robin Lee Powell wrote:

> Subject: Palm Writings + RPN
> From: Robin Lee Powell <rlpowell@digitalkingdom.org>
> To: rlpowell@digitalkingdom.org
> Date: Tue, 28 Oct 2008 18:17:34 -0700
> 
> @h1 A Completely Different RPN Solution
> 
> We could have explicit push and pop operators in KOhA.  Call them
> xa'a and xu'u, respectively.  Usage would be like so:
> 
> xa'a li pa sumji li re .i sumji li vo xu'u
> 
> The first bridi adds 1 and 2 and pushes the result onto the stack.
> The second adds 4 to the topmost stack element.
> 
> Given that, there could also be an RPN marker that would allow
> dropping the explicit push and pop, given text such as:
> 
> li pa li re te sumji .i li vo li mu te sumji .i te pilji

(etc.)

This brings back fond memories.  The mathematical expression syntax in Old 
Loglan was rather horrendous, and I was not satisfied with the grammar for 
simple dimensioned quantitites such as "I am 1.73 meters high".  When I 
worked on gua\spi I took the opportunity to define mathematical expressions 
as RPN.  This document section begins with math expressions (and continues 
with quantification, and sentence forms, which are not today's topic).
    http://www.math.ucla.edu/~jimc/guaspi/vocab2.html

In "real" RPN no explicit stack pushing and popping are needed because the 
operators have a predetermined number of arguments; they always pop all 
their arguments and then push the single result.  But if an operator had 
multiple results (e.g. quotient and remainder), or where you want to 
optimize a computation by computing a sub-expression once and then 
replicating the result, then explicit stack manipulation is needed.


James F. Carter          Voice 310 825 2897    FAX 310 206 6673
UCLA-Mathnet;  6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA 90095-1555
Email: jimc@math.ucla.edu  http://www.math.ucla.edu/~jimc (q.v. for PGP key)


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