On 16/04/2023 17:37, Jonathan Kew wrote:
First note: I see the same result with plain TeX. So not a XeTeX issue.
Agreed, but as I use only XeTeX this seemed the right place to ask. I
did test with PdfTeX (not having plain TeX in my TeXworks armoury) and
PdfTeX did much the same but put a real <tab> in the transcript as
opposed to ^^I.
Anyway, this is expected behavior. The ^^I isn't part of the offending
control sequence; it's just the preceding context on the line, which
is what normally appears in a TeX error message.
OK, so I should have realised that in the absence of a leading "\", ^^I~
could not possibly be a control sequence and therefore the "~" had to be
an active character. That fact had passed me by ...
Ignored characters are not "removed from the input" (despite anything
Eijkhout says); they're still present, just ignored.
Having consulted Eijkhout first, I did then search the TeXbook to see if
I could find a definitive statement concerning the treatment of ignored
characters but failed to do so — perhaps I should search the PDF version
rather than the printed ...
--
/Philip Taylor/
