HP15C: A Corrected Floor Function by Werner
A Corrected Floor Function
On November 25, 2023, I posted floor and ceiling functions for the HP 15C, DM42, and HP 27S calculators. I also posted the code on the Museum of HP Calculators (MoHPC).
Werner informed me that the floor code was inaccurate for x=-0.5. In fact, the code is inaccurate for all x values from -1 to 0.
The corrected code that Werner presented, by permission, on the MoHPC forum is:
Key Code : Key
__, 43, 44 : INT
42, _4, 25: x<> I
__, 43, 36: LST x
__, 42, 44: FRAC
43, 30, _2: TEST (x<0?)
42, _5, 25: DSE I (decreases I, always skips)
__, __, 16: CHS (nop)
__, __, 33: R↓
42, _4, 25: x<>I
This code works for all real values.
For the ceiling function, use the identity: ceil(x) = -floor(-x).
MoHPC thread:
https://www.hpmuseum.org/forum/thread-20766-post-182065.html#pid182065
Eddie
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