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[Android] Correct LaTeX code generates "LaTeX syntax error"

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Duong Nguyen

Hi Richard Zach, do you mind sending us the snippet of LaTex that you used and doesn't work on Android?

Richard Zach

Duong Nguyen:

Suppose you wanted to come up with axioms for set theory. Your language only has one 2-place predicate symbol, $$\in$$: $$x \in y$$ says that $$x$$ is an element of $$y$$.

The first three axioms of ZFC are:

1. Sets are extensional.

$$\forall x \forall y~(\forall z~(z\in x \leftrightarrow z\in y) \leftrightarrow x=y)$$

2. An empty set exists.

$$\exist x \forall y \lnot y\in x$$

3. Whenever $$x$$ and $$y$$ are sets, the set $$\{x,y\}$$ exists.

$$\forall x \forall y \exist z ((x\in z)\land (y\in z)\land\forall m(m\in z\rightarrow m= x \lor m = y))$$

4. Whenever $$x$$ and $$y$$ are sets, $$x \cup y$$ exists.

$$\forall x\forall y\exists z\forall c(c\in z\leftrightarrow (c \in x \lor c\in y ))$$

5. What about "Whenever $$x$$ exists, so does $$\bigcup x$$ (you might have to look up what $$\bigcup x$$ means.)

$$\forall x \exist y \forall z (z \in y \leftrightarrow \exist v (z \in v \wedge v \in x))$$

6. The power set axiom says that the power set of any set exists. (This is in the book, but let's find a single sentence in the language with just $$\in$$ that says this.)

7. Another axiom of ZF is the axiom of infinity. Let's define the successor of a set $$x$$ to be $$x \cup \{x\}$$. The axiom of infinity says that there is a set that contains the empty set, and whenever it contains $$x$$ it also contains its successor. How can we write that in the language of set theory.

Duong Nguyen

Merged in a post:

Math display issues on mobile

Sean Fitzpatrick

Some LaTeX that is understood by MathJax works fine on the web, but not on mobile (at least, not on the android app).

Here is a question here I answered with some vectors.

On web it works fine, but on mobile, the columns turn into rows. (I have other examples where the column just gets cut off.)

In the very next post, my answer that works fine on the web throws multiple LaTeX syntax errors on mobile.

Duong Nguyen

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Duong Nguyen

Hi Sean Fitzpatrick, thank you for reporting this bug. We'll add this fix to our upcoming app release.

Sean Fitzpatrick

Duong Nguyen: thank you! I just noticed another one last night: both LaTeX and MathJax allow the

*

character (e.g. T^*

notation for a dual map). This works on web but on the app it disappears and I get weird formatting bugs. I have to use \ast

as a replacement on mobile. (Maybe this is part of the same issue though.)Sean Fitzpatrick

(I also just learned that I can't type a

*

in regular text without wrapping it in code delimiters, or it disappears. So maybe it's a special character for Campuswire.)Duong Nguyen

Sean Fitzpatrick: Hi Sean, do you mind posting the snippet of LaText that you used?

Sean Fitzpatrick

Duong Nguyen: these would be using syntax like

\begin{bmatrix}a\\b\\c\end{bmatrix}

for column vectors.