# [texhax] Ref. Man. Bausum [was tabbing]

Uwe Lück uwe.lueck at web.de
Mon Sep 18 21:09:45 CEST 2006

At 23:57 15.09.06, Karl Berry wrote:

>     In my example I asked for a macro for which
>     \accent is a "hard-wired shorthand" in the previous sense.
>
>I guess it might be possible to to program the most important part of
>\accent in macros, but I don't propose to do it for the mere sake of the
>exercise :).  Here is the description of the make_accent procedure from
>tex.web:

Thanks a lot, Karl. The heart of my original problem indeed was
what font parameters \accent uses and whether a macro could

Considerable parts of the documentation in
the web source of TeX may be
what I really would like to see (and understand).
My original question was whether Bausum's manual
comes near to such an extract of the web source of TeX.
(I wanted a good reason for urging someone here
to buy it for a library.)
Anyway, if you (Karl) proceed transcribing the web source
of TeX this way, you may become the author of the Manual
that I am really waiting for ... ;-))

Possibly all my questions on what TeX really does are
answered in the web source, and I should just look at
it next time (if I'm allowed to).
Till now I had thought that I never would be
able to learn anything from the web source. (As told
somewhere else: I haven't studied computer science,
neither attended any course on programming. I only have
played a little with BASIC, Assembler, Pascal; and I am

that my accent problem has lost importance for my
jobs here since it bothered me (and that I still know
too little about implicit kerns to understand all that).

Cheers,

Uwe.

>I guess it might be possible to to program the most important part of
>\accent in macros, but I don't propose to do it for the mere sake of the
>exercise :).  Here is the description of the make_accent procedure from
>tex.web:
>
>-------------------------------------------------------------------------------
>@ The positioning of accents is straightforward but tedious. Given an accent
>of width |a|, designed for characters of height |x| and slant |s|;
>and given a character of width |w|, height |h|, and slant |t|: We will shift
>the accent down by |x-h|, and we will insert kern nodes that have the
>effect of
>centering the accent over the character and shifting the accent to the
>right by $\delta={1\over2}(w-a)+h\cdot t-x\cdot s$.  If either character is
>absent from the font, we will simply use the other, without shifting.
>-------------------------------------------------------------------------------
>
>The slant is one of the \fontdimen parameters, and the char dimensions
>could (I guess) be found by typesetting them in an \hbox, and then
>laboriously doing all the calculations ...
>
>There would be some TeXnical differences, as later on tex.web says:
>
>-------------------------------------------------------------------------------
>@ The kern nodes appended here must be distinguished from other kerns, lest
>they be wiped away by the hyphenation algorithm or by a previous line break.
>
>The two kerns are computed with (machine-dependent) |real| arithmetic, but
>their sum is machine-independent; the net effect is machine-independent,
>because the user cannot remove these nodes nor access them via \.{\\lastkern}.
>-------------------------------------------------------------------------------
>
>As far as I know, there's no way to insert such implicit kerns at the
>.tex source level.
>
>
>Cheers,
>k