Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!think.com!mintaka!ai-lab!rice-chex!bson
From: bson@rice-chex.ai.mit.edu (Jan Brittenson)
Newsgroups: comp.sys.handhelds
Subject: Re: DEC2FRAC-II for the HP48SX
Message-ID: <14476@life.ai.mit.edu>
Date: 30 Mar 91 21:48:22 GMT
References: <12222 <1991Mar30.191031.26274@en.ecn.purdue.edu>
Sender: news@ai.mit.edu
Organization: nil
Lines: 47

In a posting of [30 Mar 91 19:10:31 GMT]
   wscott@en.ecn.purdue.edu (Wayne H Scott) writes:

 > This program handles:
 >	real numbers
 >	complex numbers
 >	equations
 >	TAGGED objects
 >	lists
 >	and any combination of the above

So all we have to do now, is:

	1. Rewrite Wayne's and Joe's programs in system RPL.

	2. Write +, -, INV, SIN, etc, functions to
	   replace the keyboard equivalents. Basically, they
	   should check to see whether one of their arguments
	   is an algebraic - if not, just chain to the standard
	   function. Otherwise, we apply the standard operator,
	   EVAL, and DO->Q.

	3. Appropriate system flag -54, conveniently among
	   the "Display Format Flags" to mean "fractional
	   display." If the flag isn't set, just do the
	   standard old thing, regardless of arguments.

	4. Write a vectored ENTER function to automatically
	   DO->Q on all input, if flag -54 is set, otherwise
	   it should do nothing.

	5. Get the "maximum denominator" parameter from a
	   'FRACpar' variable instead of the stack.

	6. Add code to handle fractional units imposed by the
	   brain damage of the English unit system - Joe's
	   wish list seems like a good starting point.

	7. Package it all in a library.

   Voila' - we have an exceptionally useful fractional library.
Perhaps the most useful one ever put in a calculator? I think just
using a "display format" is the way to go, rather than trying to
implement fractions symbolically.

						-- Jan Brittenson
						   bson@ai.mit.edu