Re: [OT] Twenty Questions for DEK

[Hans Hagen <pragma@wxs.nl>]

On 5/21/2014 8:16 AM, Philipp Gesang wrote:
> http://www.informit.com/articles/article.aspx?p=2213858&WT.mc_id=Author_Knuth_20Questions
>
> Quote:
>
>     “The people at MSP wrote special software that converts my TeX
>      source text into suitable input to other software that
>      creates pdf files.”
>
> I wonder why using a TeX engine capable of producing PDF output
> directly wasn’t an option.

Ok, I think this is what sums it:

quote: "My principal goal was to make the books easily searchable—and 
that's a much more challenging problem than it seems, if you want to do 
it right. Secondarily, I wanted to let readers easily click on the 
number of any exercise or equation or illustration or table or 
algorithm, etc., and to jump to that exercise; also to jump readily 
between an exercise and its answer."

(1) The interactive bit is rather trivial: cross references, tocs and 
indices, linking answers and questions, are already generated so there 
one only needs to add some hyperlinking code (maybe some additional 
housekeeping if backlinks or in the case of indices linked backlinks are 
supported but it is probably kept simple in order not to spoil the look 
and feel.)

(2) The searching might be more complex as traditional 8 bit fonts are 
used in plain tex, so there is some tounicode magic needed (not too hard 
either, mostly housekeeping and careful checking) ... math can be 
somewhat complex there as not all is copyable, given that it's needed, 
but on the other hand, searching is also non trivial: does a reader 
search for "unicode symbol math italic i" or for just an "i"? Copying 
math demands a proper tounicode, but I bet no viewer can search for both 
kind of tagging at the same time (math alphabet stuff). Searching 
regular text of course is no issue.

(3) The question is: has more been added than just basic access as in 
books? Crosslinking books and so?

So, no rocket science, mostly careful keeping the original (not 
interfering with breaks and so) so that is probably where most of the 
work went into. If pdftex was used, one thing to keep in mind is that 
adding whatsits can interfere sometimes. This can be avoided by luatex 
but then one has to accept the fact that the output can differ (no lig 
recomposition), although that can be checked by diffing pdf's and making 
local exceptions. A nice challenge: kind of making an electronic 
facsimile i.e. don't touch (spoil) the original.

Hans

ps. An interesting audience, those asking the questions.

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