Bug: HP Prime can't do Log's

[Fortin]

(12-15-2015 07:43 AM)davimle Wrote:  OK, I was fascinated and curious about the numerical methods pathological cases posed in the paper linked by @Fortin. Now that my daughter is home with her Prime, I figured it was time for a calculator smack-down!

What I find interesting is the behavior and selection of the 1e-13 for the TI. I believe it was intentionally chosen because it is 'available' to use, but just not displayed. A digit in that place will cause rounding of the last shown decimal place (1e-12), for example.

Because the Prime doesn't play "have and hide" of this decimal place, 1e-12 may be a more appropriate test -- for it.

On the TI-85 (for example):
.1234567890123 displays as .123456789012
but
.1234567890125 displays as .123456789013

Also on the TI-85, entering: .1234567890123
And then repeatedly pressing enter to the following: Ans+1e-13
Will accumulate in the hidden decimal place until it rounds up the last shown place.

I'd rather see a complete approximate result than be wondering what it's not showing me... In other words, is that "4" really a "4" or does it just look like one? This behavior would lead to issues where '4' as a variable would not equal 4 as a number. >:-|

However, on the newer TIs, this place is dropped under certain conditions so that the displayed '4' is more likely a '4'... even if it isn't.

So, getting back to the original issue... on the TI-85, ln(81)/ln(3) returns "4". If one then evaluates: Ans==4, it returns 0 (false).