From e0c6872cf40896c7be36b11dcc744620f10adf1d Mon Sep 17 00:00:00 2001 From: Norbert Preining Date: Mon, 2 Sep 2019 13:46:59 +0900 Subject: Initial commit --- info/challenges/aro-bend/answer.014 | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 info/challenges/aro-bend/answer.014 (limited to 'info/challenges/aro-bend/answer.014') diff --git a/info/challenges/aro-bend/answer.014 b/info/challenges/aro-bend/answer.014 new file mode 100644 index 0000000000..9892558c7a --- /dev/null +++ b/info/challenges/aro-bend/answer.014 @@ -0,0 +1,27 @@ +[This was included as a self-decoding answer in the posting of Exercise +#14; see exercise.014] + +Answer to Around the Bend #14: + + Catcode Char Codes Catcode Char Codes + ------- ---------- ------- ---------- + 1 0--255 10 1--255 + 2 0--255 + 3 0--255 11 0--255 + 4 0--255 12 0--255 + 13 0--255 + 6 0--255 + 7 0--255 + 8 0--255 + +Category 10 is the exceptional case. Catcode-10 characters with character +code <> 32 can only be produced by \uppercase/\lowercase tricks (TeXbook, +Appendix D). So the pair character 0, catcode 10 is not possible: \uppercase +and \lowercase cannot produce a character 0 from a non-0 character. + +Active characters will test true for category 10 with \ifcat if they are +\let equal to a space token. But if the ~ character (say) has been so +defined, it will not match a space in the delimiter text of a macro with +delimited arguments. And according to \tracingcommands the meaning of an +active tilde that has been \let equal to a space is "blank space ", +whereas the meaning of a category-10 tilde is "blank space ~". -- cgit v1.2.3