Suggestion Personalized latex macros: hard or easy?

strangerep

When I'm typing latex math (with frequent bras and kets) in the quantum forum, I often put this first:

\def\<\rangle
\def\>\langle

because this is annoyingly ugly: ##<\psi | \phi>,~##
but this: ##\langle\psi | \phi\rangle##
is a pain to type and edit if there's a lot of it.

(There's a few other things, such as abbreviations for oft-used math characters in particular fonts).

So,... umm,... I was just wondering... is it be hard or easy to implement a (modest-sized) set of predefined macros on a per-user basis?

Fredrik

It might work to put macros in the signature*. But not all users have signatures. And a bigger problem is that if someone tries to quote something you did on an earlier page or in a different thread, the macros won't be included.

I would guess that the vBulletin developers would have to make a lot of changes to the code to make something like this work smoothly.

*) I tried to test this theory with this post, but I couldn't get any kind of signature to appear.


Note by the way that the | in your bra-ket is too short. Kets can get even uglier when we use other symbols. Example: ##|\uparrow\rangle##. This should probably be typed as \left|\uparrow\right\rangle. ##\left|\uparrow\right\rangle##. The best code I can think of for your bra-ket is this:
Result: $$\left\langle\psi\left|\,\phi\right. \right\rangle$$ But I don't even that is perfect, because the size of the | will now be determined only by the ##\phi##.

mfb

You need a signature first, before posts can be configured (!) to show this signature. If you do not have one, all new posts are created with the default setting "do not show signature".

This forum uses MathJax to show formulas, which has nothing to do with vBulletin - and the vBulletin for LaTeX code ignore the author. I doubt that default macros would work without significant coding effort.

Fredrik

Ah, you're right. The problem must have been that I created the post and started editing before I created the signature. I had no problem getting a signature to appear when I tried it a minute ago. I tried one with a LaTeX \newcommand. I put the new command in the post, but it wasn't understood by MathJax when I previewed.

OK, that makes sense.

CompuChip

I used to define a macro like

\newcommand\braket[2]{\ensuremath\left\langle #1\vphantom{#2} \mid #2\vphantom{#1} \right\rangle

especially for this. Problem is then you also need a one and three argument variant for [itex]\langle\phi\rangle[/itex] and [itex]\langle \phi \mid \hat A \mid \psi \rangle[/itex] of course.

Fredrik

I have made a mental note of that vphantom trick. I may have to use it in the future. Thanks.

Ben Niehoff

Suppose this were possible. I think you'd have a huge issue dealing with quoted posts.

For example, I have probably 100 macros I'd like to define. Things like

\newcommand{\cR}{\mathcal{R}}

for calligraphy letters, and

\DeclareMathOperator{\into}{\raisebox{0.2ex}{\reflectbox{\rotatebox[origin=c]{180}{$\neg$}}}}

for the interior product. I would show you, but it looks like MathJax can't interpret that one correctly.

Anyway, if I type up a post using a bunch of my macros, and then someone quotes it, what code should be displayed in their editing box? If macros are personalized, then they won't have access to my macros. So if my macros are used in their post, they won't work.

OK, but suppose we have the interpreter process my quoted text using my macros. Fine, but the person quoting me might remove my username. Or might try to use one of my macros himself (one way people learn Latex is by quoting one another on here).

OK, so maybe instead of showing him my code as written, it could be pre-processed to expand all macros before it is stored in the database. Then when someone quotes it, it just shows them standard Latex. They can see exactly how everything is done, the software doesn't have to remember who originally posted everything, and they can copy and paste things into their own post, and it will work fine.

Great, but now what if I need to edit one of my own posts? If all my macros get expanded before saving to the database, this will get very tedious. It looks like the only solution is to store 2 copies of every Latex-enabled post, and that is surely not a good solution, as I'm sure PF's storage requirements are already substantial (which is, in fact, why they switched to MathJax instead of their previous method).

mfb

That lead me to an interesting idea. Those macros could be used similar to Wikipedia .css changes: Every user can define his own, but other users can refer to that as well.

As an example, you create "benniehoff.tex" which is stored somewhere on the server (probably in a database and not as a file). Afterwards, it could be included like $$<benniehoff.tex> 1+2$$, where the board replaces <benniehoff.tex> by your macros. Quotes are no problem, and you don't have to re-invent the wheel every time.