# NewCommand Variables

Forums:

I don't know if this is just remnants of the server going FUBAR, but are certain characters "reserved" (i.e., off limits) for \newcommand{\__} assignment?
It appears that \a \b \c \d \i \j \k \l \o \r \t \u \v \H \L \O \P \S are all invalid, as well as anything with numbers except for single place (i.e., "\0" - "\9"): "Rendering failed. LaTeX errors:" "line ##: Emergency stop."
And some get assigned alright but crash when accessed (e.g., $\APg$).
Can one create "\newcommand" packages (would that be a type of "\usepackage"?)? If so, is there a page that explains it?
For that matter, is there a page for newbies that explains this WHOLE "package"? I'm on Wikipedia, so I know TeX to the extent that they use it. P=)

~Kaimbridge~

### Re: NewCommand Variables

I don't know, I've just been using this open entry

http://planetmath.org/?op=edit&from=objects&id=2022

for experimenting (only "previewing", not actually posting).
I was first trying to define this:

\newcommand{\oe}{o\!\varepsilon}

then started digging around and found out "\o" (amongst others) wasn't acceptable! P=(

~Kaimbridge~

### Re: NewCommand Variables

Try \renewcommand.

I just tried it for that entry and it built fine.

It is good practice to use this declaration when there is even a remote chance the command might have already been defined by another library.

I did, however, notice that jsMath mode is not working for previewing. We are going to work on fixing that now. In the mean time, you can switch your rendering mode to page images or HTML and images in your settings/preferences.
apk

### Re: NewCommand Variables

Okay, that seems to fix that aspect.
But now try \newcommand{\APe}{\widetilde{\Alpha}} and
execute $\APe$: It will define alright but will crash
when executing...but defining with \alpha DOES work!?!
And, if I attempt to define with \renewcommand it crashes
at definition.

~Kaimbridge~

### Re: NewCommand Variables

It seems the problem is with \Alpha, itself: Try $\Alpha$ in
any article!

~Kaimbridge~

### Re: NewCommand Variables

\Alpha doesn't exist in LaTeX... only \alpha works.

### Re: NewCommand Variables

I'll point James to this thread.

Are the errors showing up in all rendering modes?

apk