Re: Modulus and Non-Negative Finite Field

In article <op.uhyloqrvnn735j@xxxxxxx>,
"John H Meyers" <jhmeyers@xxxxxxxxxxxxxx> wrote:

On Mon, 22 Sep 2008 18:37:25 -0500:

| @ To recall the current MODULO value
| \<< PATH { HOME CASDIR MODULO } RCL SWAP EVAL \>>

{ HOME CASDIR MODULO } RCL is sufficient,
since it doesn't change the current path.

Right!

However, due to inheritance from the earliest HP49G,
when the variables in CASDIR were initially in HOME,
the calculator's internal functions
will use any "CAS variables" found instead in HOME,
if they are not also in CASDIR!
(move them all to HOME and see)

Purists who want to be absolutely compatible with the calculator
may therefore want to adjust for that, since
{ HOME CASDIR MODULO } RCL errors if 'MODULO' exists in HOME,
but doesn't exist in CASDIR!

\<< PATH HOME CASDIR 'MODULO' RCL SWAP EVAL \>> ???

The above accounts neither for the possible current non-existence
of CASDIR, nor for the possible current non-existence of MODULO,
even though CASDIR exists (as a directory?) --
this may serve as an indication of why programming of built-in ROM
(or of any generalized system
which hasn't control of everything in its environment)
can require more than just casual attention,
although for casual user programming purposes,
it may be suitable to just let { HOME CASDIR MODULO } RCL
error out if things aren't already exactly where most commonly found.


I had forgot that little quirk.

Thanks.
.