How to demonstrate LaTeX tags and code

[jtbell]

Does this work for illustrating itex and tex tags?

[noparse]$E=mc^2$[/noparse]

 

[jtbell]

Nope.

Is there any way to illustrate the use of tags without rendering them, besides inserting extra spaces?

[ itex ]E=mc^2[ /itex ]

 

[Borek]

[ plain] is a new [noparse]. But as the MathJax system knows nothing about UBBC tags and ignores them completely, there is currently no good way of showing these things. You can try the cyryllic trick (replacing standard ASCII e with "е") but on some computers it doesn't render correctly.

[tеx]E=mc^2[/tеx]

 

[jtbell]

That's a nice trick! The two e's look identical on my setup (Firefox, Mac OS).

 

[jtbell]

Testing another method suggested by mfb in a report thread:

##E=mc^2##

[tex]E=mc^2[/tex]

Yay! The trick is to wrap each tag in color tags, and make them black. If I use red instead:

[tex]E=mc^2[/tex]

Interestingly, the color tags don't show up when you edit or quote the post.

Oh wait, they do show up if you switch to the BBCode editor. Wow, where did all those duplicate color tags come from? oo)

Let's see if I can use the "Text Color" icon in the palette:

[tex]E=mc^2[/tex]

Yep, that works, too. You don't actually have to type out the color tags.

 

[Mark44]

Even changing the text color of one letter to black will work.
Here I have changed the 'x' in tex to black.
[tex]E = mc^2[/tex]

Next, I change the 2nd $ of the first pair to black.
$$E = mc^2$$

This might not work if you have subsequent LaTeX stuff, so might need to also change one $ in the end pair.

 

[mfb]

Yes, outside code tags that works fine. Inside it does not.

Color code does not get parsed:

[ite[color=black]x[/color]]a^2[/itex]

Same with plain (it is simply treated as regular text):

[plain][itex]a^2[/itex][/plain]

But itex does get parsed:

[itex]a^2[/itex]

 

[jtbell]

Indeed, the color-tag trick does not work inside code tags. However, it does work inside font tags, so you can put an entire code example in e.g. Courier New instead of the default Ariel:

[tex]E=mc^2[/tex]

Now I wonder what happens if I put the entire example in color tags, which is simpler than doing it for the individual tex tags...

$$E=mc^2$$

Nope, you have to do the tags individually.

 

[Greg Bernhardt]

Code this work?

\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)

##\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)##

[tex]\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)##[/tex]

 

[jtbell]

I suppose we could call that the Technicolor method.

 

[Borek]

Is this some plugin, or just XenForo?

 

[Greg Bernhardt]

Is this some plugin, or just XenForo?

https://www.physicsforums.com/threads/how-to-geshi-syntax-highlighter.773407/

 

[jtbell]

Here's something weird. Consider this code:

[tex]
u(x) =
\begin{cases}
\exp{x} & \text{if } x \geq 0 \\
1 & \text{if } x < 0
\end{cases}
[/tex]

which produces this:
$$u(x) = \begin{cases} \exp{x} & \text{if } x \geq 0 \\ 1 & \text{if } x < 0 \end{cases}$$
If you "colorize" only the [tex] tag, you get this:

[tex]
u(x) =
\begin{cases}
\exp{x} & \text{if } x \geq 0 \\
1 & \text{if } x < 0
\end{cases}
[/tex]

To make all the code display as code, you also have to colorize the LaTeX \begin{cases} command that creates the cases environment. You don't have to colorize the closing \end{cases} command. This applies to other environments as well (array, matrix, ...).

You also don't have to colorize the closing [/tex] tag, just the opening [tex]. I only realized this just now.

 

[mfb]

\begin{cases}
\exp{x} & \text{if } x \geq 0 \\
1 & \text{if } x < 0
\end{cases}

Things with begin and end get parsed without any tex tags (for whatever reason). Therefore, you have to mask them separately to prevent parsing.