Series on Blogging with LaTeX

This is the 5th and last post in this series. Previous ones:

Now I’m closing this series with some extra examples and reporting some bugs.

## Extra examples

Here I show some examples with a discussion of peculiar issues. Some other also interesting remarks can be found in the About page of Terence Tao’s blog What’s New.

### Example 1

\langle q | f ( \hat{q} ) = f (q) \langle q |

$\langle q | f ( \hat{q} ) = f (q) \langle q |$

Notice that the \left and \right are not necessary in this case, however, if used it will work:

\left \langle q | f ( \hat{q} ) = f (q) \langle q |

$\left \langle q \right | f ( \hat{q} ) = f (q) \left \langle q \right |$

### Example 2

$latex \| \vec{u} + \vec{v} \| = \| \frac{u + v}{u-v} \| &fg=aa0000&s=1$

$\| \vec{u} + \vec{v} \| = \| \frac{u + v}{u-v} \|$

Again, \left and \right were not necessary. However, if used, they can adjust the sizes of the norm frames:

$latex \| \vec{u} + \vec{v} \| = \left \| \frac{u + v}{u-v} \right \| &fg=aa0000&s=1$

$\| \vec{u} + \vec{v} \| = \left \| \frac{u + v}{u-v} \right \|$

This can be better seen in the next example.

### Example 3

$latex (\frac {x^{a^m}}{y^{b^n}} ) \quad \left ( \frac {x^{a^m}}{y^{b^n}} \right ) &fg=aa0000&s=2$

$(\frac {x^{a^m}}{y^{b^n}} ) \quad \left ( \frac {x^{a^m}}{y^{b^n}} \right )$

## Bugs

My main intention with this series of postings was to do some tests with the LaTeX support of the WordPress edition environment. It is quite likely that one could try to use here previous works involving LaTeX expressions or done in other environments with LaTeX-like coding, so I decided to check issues on portability.

I took the the Wikipedia article Displaying a formula, which is actually about formulas in Math Markup, as the main source of expressions to test here, in this environment.

Sometimes I’ve gotten parsing errors that are overcame simply by saving and reloading the post again. The process didn’t appear to be deterministic, so I guessed it was due to issues related to the connection protocol employed (file transfers usually go under UDP, so probably something could be missing on the way, I guess).

In other two situations I found a curious behavior of the parser, given that it could not parse expressions that I expected should be parseable or the behavior was inconsistent. Following I’ll show some examples.

### Bug example 1

This construction works: $latex ( 0,1 ) \; [ a,b ] \; ( 0,1 ] \; [ 0,1 ) &fg=aa0000&s=1$

$( 0,1 ) \; [ a,b ] \; ( 0,1 ] \; [ 0,1 )$

This too: $latex ( a,b ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 ) &fg=aa0000&s=1$

$( a,b ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 )$

However, this doesn’t work: $latex [ a,b ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 ) &fg=aa0000&s=1$

$[ a,b ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 )$

Furthermore, this works: $latex \left [ a,b \right ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 ) &fg=aa0000&s=1$

$\left [ a,b \right ] \; [ a,b ] \; ( 0,1 ] \; [ 0,1 )$

### Bug example 2

This expression parses : $latex {\cal ABC} &fg=aa0000&s=1$ ${\cal ABC}$

However, this doesn’t : $latex {\frak ABC} &fg=aa0000&s=1$ ${\frak ABC}$

To change the font of all the letters one has to change the declaration to: $latex {\frak A} {\frak B} {\frak C} &fg=aa0000&s=1$ ${\frak A} {\frak B} {\frak C}$

Notice that only the first letter followed the \frak declaration, while with the other fonts declarations (\cal, \rm, \sf etc) all the letters inside the braces will have their font changed. So,this is not exactly a bug, but is inconsistent with all the other font declarations.