I ran across a strange warning when trying to use the math command \choose inside the amsmath package's \align* environment:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
{n \choose k}
\end{align*}
\end{document}
Package amsmath Warning: Foreign command \atopwidthdelims; \frac or \genfrac should be used instead
The document still compiles and produces perfectly fine output. But what is causing this warning? And is there a way to get rid of it?
\chooseis short for\atopwithdelims(), and\atopwithdelimsis a TeX primitive. So in that light the word ‘foreign‘ seems quite strange; after all, amsmath, like any other TeX macro package, is built on TeX primitives. – morbusg Mar 23 '12 at 6:33\choosethat doesn't fit with the standard syntax of LaTeX commands. – egreg Mar 23 '12 at 9:23\atopwithdelims…”. – morbusg Mar 23 '12 at 13:15\choosethat triggers the warning, but only\atopwithdelims. All the part dealing with this warning should be rewritten if it wanted to cope with a variety of foreign commands. – egreg Mar 23 '12 at 13:32:-Deven though you just said it in perfect form in the previous comment: “doesn't fit with the standard syntax of LaTeX commands”. – morbusg Mar 23 '12 at 16:01