Bug: HP Prime can't do Log's

[davimle]

@ndzied1 I'd be happy to do that, can you tell me which ones of were of interest? (There are so many settings on the Prime.) I can tell you that we used Number Format = Standard ("Full-precision display", according to user guide) if that is what you were asking.

@Werner & @Fortin thank you for the clarification. My misunderstanding here. I thought from the discussion that the Prime was carrying 15 digits, but only displaying 12. (Especially since 15 digits seemed to be common across other calculators.) Sounds like intermediate answers are always rounded to 12 digits? If so, then the "error term" should be changed to 1E-12 for the Prime. (I don't have the calculator with me again, but as I recall, I had tried 1E-12 and the Prime got the right answer.) I certainly appreciate WYSIWYG, so appreciate this decision with the Prime.

In a weird twist, I wonder if people find the TI calculators to be more precise with 15 digits than the HP Prime with 12 digits? (This must give marketing folks at HP fits.)

@Time Wessman thanks again. Looking forward to a firmware update (someday) where the fix to LOG(A,B) will be included.

Thanks again everyone, this has been a very enlightening discussion. I am now very curious what the iOS built-in calculator is doing! Maybe they just carry a ridiculously large number of (pure decimal) digits? I guess this may be possible on modern computers and phones where computational speed of hand calculators is not an issue. (The manual entry is definitely the limiting factor!) Thank you @Werner for explaining that CAS mode is using binary to represent floating point numbers. I guess this is the traditional problem of binary computers trying to do decimal math. (And explains why the precision gets further off than expected.) It seems like CAS in particular would want to stay in decimal for non-integers.

It is fun to imagine a "teaching" calculator that could do decimal calculations to arbitrary precision essentially "long-hand". Seems like for anything involving manual entry we are to the point where the machine can keep up. Or maybe just switching to IEEE 754 decimal128 would be "good enough".