wester@ghostwheel.unm.edu (Michael Wester) (12/13/90)
I have been trying to understand the \length macro defined on page 219 of the
TeXbook. All is well until I try to \write out a result. In particular, I
TeX the following:
% Define \length, even to the point of using the same unreadable spacing as
% found in the TeXbook, just to be sure there that are no subtle errors.
\def\length#1{{\count0=0 \getlength#1\end \number\count0}}
\def\getlength#1{\ifx#1\end \let\next=\relax
\else\advance\count0 by1 \let\next=\getlength\fi \next}
\def\qqq{\length{argument}} % try out an example
\qqq % this causes an 8 to be written in the DVI file
\immediate\write16\qqq % however, this causes an error
The error is
! Undefined control sequence.
\getlength ... etc.
Replacing \def by \edef causes the same problem. I presume the \write causes
the same sort of expansion as \edef. So, how does one view the result
interactively (if one is debugging on a non-graphics terminal and wishes to
avoid doing frequent octal dumps) and better, how can I make the \edef and/or
\write work? A simple answer would be nice but from my experience so far, I
don't really expect TeX programming to be simple!
--
Michael Wester --- wester@ghostwheel.UNM.Edu (Internet), wester@unmb (BITNET)
Department of Mathematics, University of New Mexico, Albuquerque, New Mexico eijkhout@s41.csrd.uiuc.edu (Victor Eijkhout) (12/14/90)
wester@ghostwheel.unm.edu (Michael Wester) writes: >\def\qqq{\length{argument}} % try out an example >\qqq % this causes an 8 to be written in the DVI file >\immediate\write16\qqq % however, this causes an error >[...] I presume the \write causes >the same sort of expansion as \edef. Correct. And to add to your problems: the length macro uses not only expansion, but also assignments, which are not expandable. You can view your results interactively but having the \write *inside* the macro you are testing. Of course this is not what you want. This may be a silly solution, but I think it works: \setbox0\hbox{\qqq} \tracingonline=1 \showbox0 This shows you what's in box0 (without the \tracingonline you get this only in your log file), in particular the characters that have been typeset in it. Victor.