TeX - ! Extra alignment tab has been changed to \cr

[David Carlisle]

On Sat, 6 Jul 2019 at 13:23, Carlos <linguafalsa at gmail.com> wrote:
>
> Hello list
>
> David a few  months ago I brought  up an issue with the infamous `Extra alignment tab has been changed to \cr` error attached to it, and you said , quote
>
>> and the error is not detected until  the & which is trying to put the
>> Yes box into a third column of the table which only has two columns.
>>
>> there is no sensible way TeX could recover from this and guess your
>> original intention.
>
>
> http://tug.org/mail-archives/texhax/2019-January/023495.html
>
> And we certainly have been over this before, - even prior to the above - but I just want to confirm one more time, and based mostly on your past-past and past comments, who's to be blamed for....
>
> I thought at one time that this issue, namely the error with the misleading title of `Extra alignment tab has been changed to \cr` , was in your end of the LaTeX stick, but you threw the hands in the air and said that No no no, this is TeX fault.
>
> My question is this:
>
> Who's responsible to take care of this?

Take care of what? Sorry I do not understand your message at all (or
why you specifically sent it to me as well as the list?

> The error is misleading either by wording or whatever other term you'd like to classify it under,

Why is the error misleading?

It has two parts both of which seem clear.

.It is issued when an unexpected & is encountered
 "Extra alignment tab"

and tex's recovery action is to change the & to \cr

"has been changed to \cr"



> Would  it be Knuth himself the person to take care of fixing it?

Yes but I would be staggered if he accepted that there was any bug to fix here.


\documentclass{article}
\def\test#1#2{\hbox to 2cm{#1}}

\begin{document}

\begin{tabular}{cc}
\hbox to 2cm{working} \expandafter \cr &  \hbox to 2cm {No}
\expandafter \cr \hbox to 2cm {not working}{} &
 \test{Yes}{} \\
\end{tabular}

\end{document}

this document is a weird mix of latex and tex primitive constructs
it's not at all clear what you intend it to do, but it seems unrelated
to your question about the alignment tab error as it runs without
error?

David