(32S) Floor Function
06-03-2017, 07:47 AM (This post was last modified: 06-15-2017 01:25 PM by Gene.)
Post: #1
 Gerald H Senior Member Posts: 1,457 Joined: May 2014
(32S) Floor Function
For real input the programme returns Floor of input without disturbing the stack.

Improvements most welcome.

Code:
 0.    LBL “F” 1.    X>=0? 2.    GTO O 3.    STO F 4.    FP 5.    STO G 6.    ABS 7.    X≠0? 8.    RCL/ G 9.    RCL+ F 10.    LBL O 11.    IP 12.    RTN
06-29-2017, 04:02 PM
Post: #2
 c785 Junior Member Posts: 33 Joined: Apr 2017
RE: (32S) Floor Function
I'm not familiar with the 32S, but on the 42S I just solved this myself using the code in the picture (it's labeled "80" because I made it part of a KEYG/MENU structure). It did take me a while though, I'm only just getting used to RPN and its quirks.

06-30-2017, 07:05 AM
Post: #3
 Werner Senior Member Posts: 608 Joined: Dec 2013
RE: (32S) Floor Function
Doesn't work for -0.999999999999 (-1 + 1e-12), or in general for
-9.9999999999x Eyyy, x=5..9, yyy>=-1
(both the 32S and 42S versions, BTW)

The easiest way without stack preservation is

Code:
>LBL "FLOOR"   RCL ST X  (or ENTER X<>Y)   1   MOD   -   END

I don't have a 32S so I don't know what commands are available there.
For the 41/42S, one version with stack preservation is as follows:

Code:
>LBL"FLOOR"  IP  X<>Y  X<> ST L  X<Y?  DSE ST Y        always skips >LBL 00  X<> ST L  X<>Y  END

Cheers, Werner
06-30-2017, 07:23 AM
Post: #4
 c785 Junior Member Posts: 33 Joined: Apr 2017
RE: (32S) Floor Function
(06-30-2017 07:05 AM)Werner Wrote:  Doesn't work for -0.999999999999 (-1 + 1e-12), or in general for
Are you sure? I just tried, the 42S code works fine on Free42 and on the DM42.
06-30-2017, 08:51 AM
Post: #5
 Werner Senior Member Posts: 608 Joined: Dec 2013
RE: (32S) Floor Function
I'm sure ;-)
Free42 and DM42 work with 34 digits, so there, take (-1 + 1e-34)

Werner
06-30-2017, 11:31 AM (This post was last modified: 06-30-2017 11:31 AM by c785.)
Post: #6
 c785 Junior Member Posts: 33 Joined: Apr 2017
RE: (32S) Floor Function
OK, you're right. "IP" after "+" isn't a good idea, so replace the sequence
Code:
+ IP
with
Code:
X<>Y IP +
and everything should be OK. Now even -1+10^-34 gives the right result on the DM42.
06-30-2017, 02:58 PM
Post: #7
 c785 Junior Member Posts: 33 Joined: Apr 2017
RE: (32S) Floor Function

Code:
> LBL "FLOOR"   IP   RCL- ST L   X>0?   DSE ST L   CLX   X<> ST L   RTN
07-01-2017, 10:16 AM
Post: #8
 Werner Senior Member Posts: 608 Joined: Dec 2013
RE: (32S) Floor Function
LastX is not correct ;-) In my version above, it is.
Werner
07-02-2017, 09:29 AM
Post: #9
 c785 Junior Member Posts: 33 Joined: Apr 2017
RE: (32S) Floor Function
You're right once again. The only thing I'd do differently is the "nop" command -- a label there is quite misleading and can lead to trouble when the code is part of a larger program, so I prefer "X<>X" in its place.

In any case, RPN is great. What I could have done with RPL in about five minutes now took me several days to grasp. But I did learn a thing or two.
07-02-2017, 10:18 AM
Post: #10
 Werner Senior Member Posts: 608 Joined: Dec 2013
RE: (32S) Floor Function
X<> ST X is two bytes, and I have a label there for the CEIL function to jump to ;-)

Code:
 { 38-Byte Prgm } >LBL"CEIL"  INT  X<>Y  X<> L  X>Y?  ISG Y        always skips  X<=Y?        nop  GTO 00 >LBL"FLOOR"  INT  X<>Y  X<> L  X<Y?  DSE Y        always skips >LBL 00        not a nop  X<> L  X<>Y  END

Cheers, Werner
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