Timeline for UnsameQ exhibits different behavior than !SameQ
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 24, 2019 at 14:13 | comment | added | Michael E2 | Much of this is discussed under the "Background and Context" section of the doc pages for SameQ, UnsameQ, Equal and Unequal. For instance, "Unequal[Subscript[expr, 1],Subscript[expr, 2]] returns True if Subscript[expr, 1] and Subscript[expr, 2] are numerically unequal, False if they are equal and unevaluated if equality cannot be established." I suppose {} and 3 are not numerically unequal, since {} is not numerical. | |
| Jan 24, 2019 at 13:23 | comment | added | Aharon Naiman | @Michael E2, thank you for your reply. Yes, I also played with !SameQ[]. I see that !Equal[] and UnsameQ[] are different, my questions are: why? and why should I have known that? Also, I would appreciate a pointer to some documentation, explaining why {}!=3 does not return False. Thank you. | |
| Jan 23, 2019 at 22:13 | history | edited | m_goldberg | CC BY-SA 4.0 | deleted 14 characters in body; edited title |
| Jan 23, 2019 at 21:01 | comment | added | Michael E2 | Perhaps you want Replace[list, x_ /; x =!= 3 -> w, 1] or Replace[list, x_ /; x =!= 3 -> w, Infinity] | |
| Jan 23, 2019 at 21:00 | comment | added | Michael E2 | ! SameQ[] would be {-7, 3, 2} /. x_ /; ! (x === 3) -> w, which returns the same as UnsameQ[]. But ! Equal[] is different than UnsameQ[], as your 2nd and 4th examples show. | |
| Jan 23, 2019 at 20:53 | answer | added | MikeY | timeline score: 3 | |
| Jan 23, 2019 at 18:05 | answer | added | GenericAccountName | timeline score: 6 | |
| Jan 23, 2019 at 15:26 | comment | added | Aharon Naiman | @Kuba, thank you for your reply. However, I do not fully understand. Apparently in the UnsameQ[] case, the entire {-7,3,2} is becoming x (/after/ the first level?) and not the same as 3. Why does that not continue with Unequal[]? (For that matter, I am a tad stymied why {}!=3 does not return False.) | |
| Jan 23, 2019 at 14:37 | comment | added | Kuba | {a} /. _ -> "who said it works only at the first level?" and {} != 3 vs {} =!= 3. | |
| Jan 23, 2019 at 14:26 | history | asked | Aharon Naiman | CC BY-SA 4.0 |