[texhax] TeX Queries (1)

[Paul Stanley]

 > 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!

Paul S : yes, I shall hang my head in shame for the next 30 years. :)

 > 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.)

Paul S: so let me get this right, `^^{ ... }' is not for inserting 
margin notes?  The TeXBook says it ``stand for a silent index 
entry''.  What does the single up arrow construct (`^{...}') do?  TBH 
I'm getting a bit confused now.

 > 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 <elipsis>

Paul S : Could you elaborate on this please? Is there a reference 
table for these values and their respective chars?

 > 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
 > improvement 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.

Paul S : beautifully explained. Thank you.

Cheers,
Paul