嵌套对齐环境的替代方案

Question

我有兴趣产生类似于以下嵌套对齐环境产生的效果。

\documentclass{article}

\usepackage{amsmath}

\begin{document}
\begin{align*}
  A = ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 +10 + 11 + 12 \\
          &
            \begin{aligned}
              {} + 2 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 \\
                      &
                        \begin{aligned}
                          {} + 3 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 \\
                                  & + 1 + 2 + 3 + 4))
                        \end{aligned}
            \end{aligned} \\
          &
            \begin{aligned}
              {} + 2 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8\\
                      & + 1 + 2 + 3 + 4 + 3 + 5 + 6 ))
            \end{aligned}
\end{align*}
\end{document}

有没有一种语法不太复杂的方法来产生这种效果？

Answer 1

使用可变制表位时，嵌套aligned是不可避免的。但您可以减少{}输入并使其更清晰。

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{align*}
  A = ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 \\
          & + 2 ( \begin{aligned}[t]
                  1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 \\
                    & + 3 ( \begin{aligned}[t]
                            1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 \\
                              & + 1 + 2 + 3 + 4))
                            \end{aligned}
                  \end{aligned} \\
          & + 2 ( \begin{aligned}[t]
                  1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8\\
                    & + 1 + 2 + 3 + 4 + 3 + 5 + 6 ))
                  \end{aligned}
\end{align*}

\end{document}

Answer 2

在我看来，嵌套aligned更优雅，但这是使用array构造的另一种选择。数组自然更紧密，因此可以添加\renewcommand{\arraystretch}{1.2}以使行稍微间隔开。

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\noindent First with nested \verb|aligned|:
\begin{align*}
  A = ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 +10 + 11 + 12 \\
          &
            \begin{aligned}
              {} + 2 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 \\
                      &
                        \begin{aligned}
                          {} + 3 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8 \\
                                  & + 1 + 2 + 3 + 4))
                        \end{aligned}
            \end{aligned} \\
          &
            \begin{aligned}
              {} + 2 ( 1 & + 2 + 3 + 4 + 5 + 6 + 7 + 8\\
                      & + 1 + 2 + 3 + 4 + 3 + 5 + 6 ))
            \end{aligned}
\end{align*}
%
And with \verb|array|:
%
\setlength{\arraycolsep}{0pt}
\begin{equation*}
\begin{array}{rlll}
  A = ( 1 & \multicolumn{3}{l}{{}+ 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 +10 + 11 + 12} \\
          & {} + 2 ( 1 & \multicolumn{2}{l}{{}+ 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10}\\
          &            & {} + 3 ( 1 & {}+ 2 + 3 + 4 + 5 + 6 + 7 + 8 \\
          &            &            & {}+ 1 + 2 + 3 + 4))\\
          & {} + 2 ( 1 & \multicolumn{2}{l}{{}+ 2 + 3 + 4 + 5 + 6 + 7 + 8}\\
          &            & \multicolumn{2}{l}{{}+ 1 + 2 + 3 + 4 + 3 + 5 + 6 ))}\\
\end{array}
\end{equation*}

\end{document}