[texhax] TeX Queries (1)

[Paul Isambert]

Le 09/07/2012 17:19, Paul Stanley a écrit :
> Hi folks
> A few Tex queries from the TeXBook. I'm looking at the TeX source, 
> however, you can download the PDF version at 
> http://net.ytu.edu.cn/share/%D7%CA%C1%CF/texbook.pdf :

Bad, bad Paul!

> chapter 1, page 1, paragraph 1:
> English words like `technology' stem from a Greek root <elipsis> which 
> is an uppercase form of $\tau\epsilon\chi$.^^{TeX (actually \TeX), 
> meaning of} ^^|\tau|^^|\epsilon|^^|\chi|
>
> Does `^^{ ... }' signify a margin note?  I'm calling it a margine note 
> because it appears separate from the main text on the right edge of 
> the page.

The whole situation with `^{...}' deals with the index; it is explained 
lines 23907 and following of the sources. (That the expressions are in 
the margin is only for proofreading.)

> chapter 2, page 3, paragraph 2:
> In the first place, there are two kinds of <elipsis> that shows up as 
> something like {\tt\char'22}, and an apostrophe or right-quote that 
> looks like {\tt\char'15} or {\tt\char'23}.
>
> `\char' according to some web sources maps numeric values to their 
> corresponding unicode characters.  in the above extract the macro is 
> separated from the numeric value by an apostrophe. I've seen both a 
> grave accent (`) and a double quote mark (") used in examples on the 
> web. Do the symbols declare different things about the number that 
> follows them?

The syntax is: \char<number>; and a number can be octal (prefixed with a 
single quote) or hexadecimal (double quote), and of course decimal 
(unprefixed). For the grave I can't see any usage but denoting a number 
via a character, i.e. `\a (meaning 97, with the backslash optional in 
this case).

By the way, \char<number> simply typesets the character at position 
<number> in the font and has nothing to do with Unicode (especially as 
legacy TeX knows nothing of Unicode).

> finally, what's the difference between `\eject' and `\vfil\eject'?  I 
> understand `\ject' forces a page break.  A `\vfil' prefix I hear 
> improves/mitigates the visual effect of `\ject' in certain circs.  
> Unfortunately, the text doesn't explain exactly what form the 
> improvmenet takes.  Any clues would be appreciated.

The \vfil means the page will be flushed upwards, unless equivalent or 
stronger \vfil's are used elswhere. For instance:

     paragraph1

     paragraph2

     \eject

will create a page with paragraph1 at the top and paragraph2 at the 
bottom because the only adjustment possible to fill the page is to 
stretch the interparagraph glue; \vfil avoids that.

Best,
Paul