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+--- Thread: (12C) Signum Function (/thread-12529.html)
Pages: 1 2
RE: (12C) Signum Function - Dieter - 03-04-2019 10:49 AM
(03-03-2019 06:52 PM)Gerson W. Barbosa Wrote: That’s what I get on my TI 57, but on my 12c Prestige (and on the latest Platinums, I presume), arguments on the display cannot be reused after an operator.
But it seems to have worked on early 12CPs, as Robert noted.
(03-03-2019 06:52 PM)Gerson W. Barbosa Wrote: IMHO, this is a feature, not a bug. Although the old behavior is apparently more convenient in some situations, I prefer this new one
I prefer the other way as it can shorten and simplify quite a lot of calculations. For instance the sum formula (n²+n)/2, that's simply + x² / 2. Add an "=" before the division, if required.
On some (many, most, all?) TIs, e.g. the 58/59, there even was a way to re-enter the displayed value during a calculation by means of the CE key, as in
5 x ( CE + 1 ) / 2 =
I really appreciated this as it helped overcome the limitations of AOS (a bit).
But then...
(03-03-2019 06:52 PM)Gerson W. Barbosa Wrote: (or at least I would if I chose ALG, which I never will).
That's what I really love about RPN: it's direct, straightforward and unambiguos. It simply does what you tell it to do and intermediate results can be freely stored on the stack.
Dieter
RE: (12C) Signum Function - Dieter - 03-04-2019 10:57 AM
(03-02-2019 03:00 AM)Gerson W. Barbosa Wrote:Code:
01 ENTER
02 CHS
03 x<=y
04 CHS
05 x=0
06 n!
07 /
That's a nice one. I probably would have used e^x to convert 0 into 1, but n! does it either, and maybe it's a tiiiiiiiiiny bit faster.
This also makes a nice ABS code:
Code:
01 ENTER
02 CHS
03 x<=y
04 CHSThis leaves the original input in Y and its absolute value in X.
And again it does not have the problems of the x² √x method: it neither underflows for very small values not does it cause inaccuracies for about one out of five arguments (cf. Thomas' post).
Dieter
RE: (12C) Signum Function - Gerson W. Barbosa - 03-04-2019 08:11 PM
(03-04-2019 10:57 AM)Dieter Wrote: This also makes a nice ABS code:
Code:
01 ENTER
02 CHS
03 x<=y
04 CHS
This leaves the original input in Y and its absolute value in X.
In order to use that as a function I’d rather get rid of the original input, but I cannot do it in less than five steps on the HP-12C:
Code:
01 0
02 x<=y
03 x<>y
04 -
05 CHSOn the HP-25 it can be done with four steps:
Code:
01 0
02 x>y
03 x<>y
04 -It won’t beat the usual method, though:
Code:
01 x^2
02 sqrt|-3.43142| = 3.431420001 might not be much of problem for most applications, I think.
Gerson.