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

[Ian Collier]

>douglas.waud at umassmed.edu (doug waud) writes:
>So now the question became how did the breaks get rhough TeX's innards 
>but not the nobreaks.

>I think the answer may lie on page 314 in the answer to exercise 14.10.
>There it says that if you have two penalties in a row TeX takes the 
>lower one. Now, the log output indicated a penalty of about 100 without 
>the an inserted nobreak (I did not chase down where this came from; I 
>suspect it would be found in the definition of \noeqalignno) so adding 
>one of 10000 would do nothing.

This is true.  The definition of \eqalignno starts with the token \displ at y
which adds \jot to the inter-line spacing and sets up an \everycr to add
\interdisplaylinepenalty between adjacent lines.  The default value of
\interdisplaylinepenalty just happens to be 100.

>Now it would appear that the behaviour matches the Texbook except for 
>the original statement you reported on P 193. Is the Texbook is 
>self-contradictory.

I don't have the TeXbook with me at the moment so I don't know how it
explains the above - but looking up \interdisplaylinepenalty may help.
-- 
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