mathclap：未定义的控制序列

Question

在我的序言中，我加载了amsmath和geometry包，并且我读到的许多其他包在使用时很有用\mathclap。这是我的序言

\documentclass[a4paper,oneside,abstracton]{scrartcl}


\usepackage[utf8]{inputenc}
%\usepackage[latin1]{inputenc}               %Zeichencodierung Text
\usepackage[T1]{fontenc}                     %Schriftsatz Dokument


%%Language settings
\usepackage[english]{babel}                  %ngerman for German
\usepackage{csquotes}                        %[babel,quotes=english]
\usepackage{caption}
\addto\captionsenglish{\renewcommand{\contentsname}{Table of Contents}}
%\renewcommand{\contentsname}{Table of Contents}   % only works when not using babel


%%Math, astro, chemical packages and options
\usepackage{amsmath,amssymb,amsthm,amsfonts,amsbsy,latexsym}
\usepackage{wasysym}                        %astronomical symbols
%\usepackage[version=3]{mhchem}             %Chemie-Package
\providecommand{\e}[1]{\ensuremath{\times 10^{#1}}}

%\usepackage{dsfont}
%\usepackage{enumerate,url}


%%Paper adjustments
\usepackage{graphicx}
\usepackage{epstopdf}                        %if problems with importing .eps graphics
%\usepackage{a4wide}                         %obsolete and replaced by geometry
\usepackage[a4paper,bottom=3.1cm]{geometry}  %also with command \geometry{options}
\usepackage{changepage}
\usepackage{titling}
\usepackage{booktabs}
\usepackage{lscape}
\usepackage{multirow}
\usepackage{threeparttable}
%\usepackage{subfigure}                      %obsolete
\usepackage{subcaption}                      %cannot be used with subfigure
%\usepackage{subfig}
%\addto\captionsngerman{\renewcommand{\figurename}{Fig.}}
\usepackage{afterpage}
\usepackage{textcomp, gensymb}               %textcomp before gensymb gets rid of the warnings "not defining \micro and \perthousand
\usepackage{soul}                            %for customised working with the text 
\usepackage{array}
\setcounter{secnumdepth}{4}                  %sets the section number depth
\setcounter{tocdepth}{4}                     %sets the ToC depth
%\usepackage{verbatim}                       %for multiline comments using\begin or \end
\usepackage{xcolor}                          %colour e.g. parts of equations

%% Control the fonts and formatting used in the table of contents.
%\usepackage[titles]{tocloft}

%% Aesthetic spacing redefined
%\setlength{\cftbeforechapskip}{}
%\setlength{\cftbeforesecskip}{0.5ex}
\setlength{\parindent}{0pt}                  %kein Einrücken von neuen Abschnitten
\usepackage{afterpage}                       %to avoid space before landscape-environment

我仍然会收到错误

\begin{equation*}
\begin{aligned}
...&\stackrel{\mathclap}{\rightarrow}
\end{aligned}
\end{equation*}

首先，我只有“align”而不是“aligned”。那些未定义的控制序列消失了，但被未定义的控制序列所取代\mathclap（这已经是在无法识别的命令之前了……我想知道为什么）。不幸的是，我的文档有太多错误，无法显示最近必要的必要更改。

Answer 1

该宏\mathclap在包中定义mathtools：

\usepackage{mathtools}

该宏接受一个可选参数作为数学样式，以及一个强制参数作为数学内容，后者被放在一个零宽度框中并居中。因此，

\stackrel{\mathclap}{\rightarrow}

没有意义，因为\mathclap缺少强制参数。