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author | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
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committer | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
commit | e0c6872cf40896c7be36b11dcc744620f10adf1d (patch) | |
tree | 60335e10d2f4354b0674ec22d7b53f0f8abee672 /info/challenges/aro-bend/answer.003 |
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diff --git a/info/challenges/aro-bend/answer.003 b/info/challenges/aro-bend/answer.003 new file mode 100644 index 0000000000..05df61fac6 --- /dev/null +++ b/info/challenges/aro-bend/answer.003 @@ -0,0 +1,55 @@ +[Posted to info-tex on 25 Oct 91; see answer.001] +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +"*** Exercise 3 (fast): +"What's the most important difference between \- and +"\discretionary{-}{}{}? + +The most important difference between \- and \discretionary{-}{}{} is +that the latter always puts in the character from font position 45 +("2D, '55) of the current font when a word must be broken at the end of +a line; \- puts in the character from font position \hyphenchar of the +current font, which is NOT NECESSARILY position 45. It would be rather +unusual for \hyphenchar to be something other than 45; in certain +special applications, however (possibly in some foreign languages as +well?) a variant value of \hyphenchar can be useful. I have an idea for +using this in a future exercise . . . + +Credit to Donald Arseneau for a correct answer. Thanks to Peter +Schmitt for providing the perfect opening for another point +I wanted to make: + +> The TeXbook states explicitly: +> \- is equivalent to \discretionary{-}{}{} +> and both are internal. +> I do not see where to the question aims: +> - control symbol : control sequence +> - no paramaters : three parameters +> - two characters : 21 characters to type +> ??? + +Schmitt is quoting from the last page of Chapter 25; the point is, +that in newer versions of the TeXbook that sentence has been revised. +I'm not sure what the latest printing says, since I don't have a copy, +but I think it simply refers the reader to Appendix H, where the +significance of \hyphenchar is explained. \hyphenchar is a feature that +was added late in the development of TeX82 (TeX82.bug reveals that is +was not added until May 25, 1983). Even if the source files for the +TeXbook were immediately updated by Knuth at that time, the changes did +not appear in the published version being sold to the general public +until some time later when the first revised edition was published, +which was no earlier than October 1984, the date of the TeXbook copy +that I have on hand, and probably later. + +The statement of purpose in `Around the bend' #1 said something +about finding the `best solution', but conspicuously failed to define +what `best' should mean in this context. It was my intention to address +this question in future exercises; for now, let me just say that I +don't intend to arbitrarily rule out of consideration answers such as +Schmitt's `two characters : 21 characters to type', since depending on +how you look at it, it could be argued that this is much more +significant than dumb old \hyphenchar minutiae. I promised that these +exercises would be challenging; that means, among other things, that +they won't always be well-defined, well-bounded, or well-behaved, and +part of the job of finding the `best solution' will be to decide what +parts of the problem need to be specified further, and to examine the +ramifications of alternatives. |