# [texhax] Re:\noalign{\nobreak} seems not work!

Ian Collier imc at comlab.ox.ac.uk
Wed Aug 13 18:39:30 CEST 2003

romeomedina at libero.it writes:
>My copy is the fourteenth printing, 1988, and on page 193 it says:

>	In fact, you can /force/ a page break after a particular line if you insert
>	\noalign{\break}' after the \cr for that line; and you can /prohibit/
>	such a break if you insert \noalign{\nobreak}'. You can prohibit /all/
>	breaks in an \eqalignno if you enclose the whole works in a \vbox:
>	etc...

That seems to confirm my suspicion that it got changed in an earlier
version of plain.tex.

I suppose if you want to prevent a line-break only at some places in
your alignment then you could hack it with something like:

\def\disallowbreak{\global\interdisplaylinepenalty=10000 }
\def\allowbreak{\global\interdisplaylinepenalty=100 }

then you can allow or disallow breaks at will.

I was going to suggest writing a macro that combines these with \cr to
make a no-break version of \cr but so far the TeX processor defeats me
(it doesn't count my new macro as the end of a cell in the alignment
and thence gets into a mess).
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