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ijabbott · (This post was last modified: 07-14-2018 12:59 PM by ijabbott.)

(07-14-2018 12:00 PM)Albert Chan Wrote:
Quote:Just the shown result. It's basically just a textual copy and paste operation.

Too bad. TI calculator sounded almost perfect.

Have you tried to prove it is really a textual copy ?

Yes, by doing 5/9 in "fixed 2" format, giving a displayed result of 0.56. The "ans" variable is full precision, so ans*9 gives 5.00. But copy and pasting the 0.56 result and multiplying by 9 gives 5.04.

You can copy and paste the expression that produced the result instead of copying the result, but if the expression is part of a chain using the "ans" variable, then it will use the current "ans" instead of the original "ans", so that might not work.

Quote:The "tape" might had the full-precision results memorized.

Only the last result in "ans" (and values in other variables) are full precision. The "tape" is just nicely marked up text.

Quote:On my iPad, I use sci:pro calc.
It also have a "paper tape" you can grab previous result.

Although the grabbed result look like a textual copy, it is actually in full precision:

Quote:Sci:Pro Calculator History

9 SIN COS TAN =
0.0174549999

0.0174549999 ARCTAN ARCCOS ARCSIN =
9

9 - 9 =
3.7358621062e-33

All intermediates were grabbed from the tape, then minus 9, for the calculator forensic test.

On the TI (and also Casio calculators), you'd just use the ans (or Ans) variable to do that.

The TI's result of the forensic test using "ans" isn't as precise as your Sci-Pro (which I guess uses 64-bit IEEE-754 format internally?). The displayed 10-digit result is 9.000001077 and the internal 13-digit result is 9.000001077372. That's a separate issue though.

For comparison, the fx-991EX does better on the forensic test with a displayed 10-digit answer of 9.000000012 and an internal 15-digit answer of 9.00000001178352. (I'm not sure the calculator really has an internal 15-digit precision answer, as simple calculations such as 1e-12+1-1 = 1e-12 versus 1e-13+1-1 = 0 suggests it only has 13 digits.)

On the TI, if you copy and paste the 10-digit displayed results from the history after each individual operation, the TI gives a final answer of 8.989942773, which is obviously less accurate than using the "ans" variable.