Timeline for Suggestions for good notation
Current License: CC BY-SA 2.5
24 events
| when toggle format | what | by | license | comment | |
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| Aug 6, 2022 at 5:19 | comment | added | teika kazura | )Ouch.( - Graham, Knuth and Patashnik, p 63. In fact it's a joke about the failed attempt to use $]x[$ to mean $\lceil x \rceil$. | |
| Dec 17, 2021 at 5:23 | comment | added | LSpice |
Of course the best notation for intervals is \open a b and \closed a b, or whatever name makes sense to you, and then you can \newcommand\open[2]{(#1, #2)} or whatever you please and leave the journal to change it if they insist. 😁 (If you like the French style, then \newcommand\open[2]{\mathopen]#1, #2\mathclose[} will space properly, like $\mathopen]x, y\mathclose[ \cup \mathopen]a, b\mathclose[$, and you can forget about \mathopen and \mathclose having once made the definition.)
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| Sep 1, 2015 at 23:43 | comment | added | Akiva Weinberger |
@WillieWong The easiest fix is ${[x,y[}\cup{]a,b[}$ — note how the curly braces separate the intervals. To compare, the original is $[x,y[\cup]a,b[$, the braced-version is ${[x,y[}\cup{]a,b[}$.
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| May 18, 2015 at 19:21 | comment | added | LSpice | @RossChurchley, another nice advantage of that notation is how easily it generalises: $x \ltimes y$ lives in a semi-direct product, $x \otimes y$ lives in a tensor product, $x \wedge y$ lives in a wedge product, …. | |
| Dec 26, 2013 at 6:18 | comment | added | Włodzimierz Holsztyński | @Qfwfq: perhaps this could be an option, perhaps a tricky option when things get complicated. My notation above is a part of my system. | |
| Dec 25, 2013 at 0:52 | comment | added | Qfwfq | @Wlodzimierz: isn't it better to use the less bombastic $f^{\circ n}$ for composition powers? (and $f^{\circ (-1)}$ for the composition inverse, to nitpick) | |
| May 3, 2013 at 18:04 | comment | added | Włodzimierz Holsztyński | Actually the power notation can be used for any 2-argument operation. For instance: $$n\cdot a\ \ :=\ \ \sum^n a$$ and $$a^n\ \ :=\ \ \prod^n a$$ Etc. | |
| May 3, 2013 at 18:01 | comment | added | Włodzimierz Holsztyński | I've always used semicolon for intervals: $$(a;b)\qquad [a;b)\qquad (a;b]\qquad [a;b]$$ Also, for composition of functions, to avoid a confusion with multiplication, I use $\bigcirc^n f$ for powers, and in particular $\bigcirc^{-1}f$ for the inverse. | |
| Dec 18, 2010 at 12:52 | comment | added | Marcel Bischoff | I also learned it like $]a,b[$ in school (Germany) but since I am reading research articles I got used to $(a,b)$. | |
| Oct 26, 2010 at 18:00 | comment | added | Beren Sanders | I could be wrong, but I was kind of under the impression that this notation ]a,b[ is more common than (a,b) in France. | |
| Oct 22, 2010 at 19:38 | comment | added | Zsbán Ambrus | I prefer Knuth's notation, which uses $ (a.\,.b) $ for the open interval and $ [a.\,.b] $ for the closed one. | |
| Oct 22, 2010 at 5:26 | comment | added | timur | It was used also in the former Soviet block. | |
| Oct 22, 2010 at 0:58 | comment | added | Hsien-Chih Chang 張顯之 | \ullcorner and \ulrcorner are nice, I've thought about it! | |
| Oct 21, 2010 at 17:22 | comment | added | Willie Wong |
@Ryan Reich: Quadrescence's example is only annoying when improperly typeset. Look at the difference in LaTeX between $[x,y[\cup]a,b[$ [x,y[\cup]a,b[ versus $\left[x,y\right[\cup\left]a,b\right[$ \left[x,y\right[\cup\left]a,b\right[.
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| Oct 21, 2010 at 16:18 | comment | added | Ryan Reich |
This won't render, I bet, but how about \ullcorner and \ulrcorner from MnSymbol? Or \lwavy/\rwavy from the same package (see symbols-a4.pdf, page 55). They both have a suitable "open" feel, and I especially like the first since they are, literally, brackets which are open.
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| Oct 21, 2010 at 13:12 | history | made wiki | Post Made Community Wiki by Ben Webster♦ | ||
| Oct 21, 2010 at 12:28 | comment | added | Hsien-Chih Chang 張顯之 | It seems that we need a new notation which is better than both $(a,b)$ and $]a,b[$... any idea? | |
| Oct 21, 2010 at 7:51 | comment | added | Suvrit | The notation $]a, b[$ is ok, except that it makes some text editors (while doing paren-matching) balk. | |
| Oct 21, 2010 at 6:48 | comment | added | Denis Serre | The point is that $]a,b[$ is the French way to write the open interval (this explains Harry's comment). It is still taught in high school, and students never learn about $(a,b)$, even at university. Only researchers adapt to this notation once they write in English. I agree that $]a,b[$ is clearer. | |
| Oct 21, 2010 at 6:30 | comment | added | Ryan Reich | I was a fan of this notation until I read Quadrescence's comment. | |
| Oct 21, 2010 at 4:55 | comment | added | Harry Gindi | Bourbaki does this, and I'm a fan. | |
| Oct 21, 2010 at 4:36 | comment | added | Quadrescence | I have to -1 this one. Nothing annoys me more than seeing $[x,y[ \cup ]a,b[$ and such. | |
| Oct 21, 2010 at 3:51 | comment | added | Ross Churchley | For a similar reason, Munkres uses $a\times b$ instead of $(a,b)$ for an element of $A\times B$. | |
| Oct 21, 2010 at 2:18 | history | answered | Hsien-Chih Chang 張顯之 | CC BY-SA 2.5 |