I used a * in a bsmallmatrix and found a curious effect. If I write \\* the * is not printed whereas with \\ * it is. Do you guys know why this happens?
My tiny example and screenshot follow below:
\documentclass[12pt]{article}%, border=2pt]{standalone}
\usepackage{mathtools}
\begin{document}
[
\begin{bsmallmatrix}a&a\&\end{bsmallmatrix}
]
[
\begin{bsmallmatrix}a&a\ &\end{bsmallmatrix}
]
\end{document}
AMS matrices use a modified form of lookahead that does not skip white space looking for * and [ this is so that you can have
\begin{matrix}
a & b \\
[x] & y
\end{matrix}
with the [ taken as text to be printed not (as it would in a standard array environment} be equivalent to \\[x] and give an error that x isn't a valid length.
* is similar to [ as the array \\ command has a * form \\* even though it is equivalent to \\ as there is no page breaking. (\\* generally is a line break that does not allow a page break at that point).
\\*almost worked "for free" in longtable. – David Carlisle Aug 14 '20 at 08:11\begin{array}{cc}instead of\begin{matrix}and you'll get the error. – campa Aug 14 '20 at 13:43\documentclass{article}\begin{document}$\begin{array}{cc}a & b \\ [x] & y\end{array}$\end{document}does give an error. – David Carlisle Aug 14 '20 at 13:43mathrools/ the AMS matrices avoids this problem -- sorry about that! – jessexknight Aug 14 '20 at 14:31\\ [xxx], and the obvious fact that math expressions are often wrapped in square brackets. – barbara beeton Aug 14 '20 at 21:04\\to which you refer is really just double-backslash, not double-backslash-space, and you are just working around MathJax escaping, right? – LSpice Aug 14 '20 at 21:47\\and the[– David Carlisle Aug 14 '20 at 21:52\\command", thethere isn't part of the command name, right? (I know you are also referring to the issue of whitespace following that command.) – LSpice Aug 14 '20 at 22:09