如何将新值传递给键而不覆盖其他值

Question

动机

我正在编写一个自定义\Paragraph命令，旨在用于align-type 环境中。

代码

这就是它。它目前的表现符合预期，但看看问题以下。

\documentclass{article}
\usepackage{xparse,amsmath}

\NewDocumentCommand{\Aligned}{O{t} m}{
    \begin{aligned}[#1]#2\end{aligned}
}

\ExplSyntaxOn

% define keys
\keys_define:nn { Paragraph }{
    beforeparagraph  .tl_set:N = \l__Paragraph_beforeparagraph_tl,
    beforehead  .tl_set:N = \l__Paragraph_beforehead_tl,
    width .tl_set:N = \l__Paragraph_width_tl,
    afterhead .tl_set:N = \l__Paragraph_afterhead_tl,
    beforebody .tl_set:N = \l__Paragraph_beforebody_tl,
    bodyindent .tl_set:N = \l__Paragraph_bodyindent_tl,
    afterparagraph .tl_set:N = \l__Paragraph_afterparagraph_tl,
}

\cs_new_protected:Nn \Paragraph_beforeparagraph:n{#1}
\cs_new_protected:Nn \Paragraph_beforehead:n{#1}
\cs_new_protected:Nn \Paragraph_width:n{#1}
\cs_new_protected:Nn \Paragraph_afterhead:n{#1}
\cs_new_protected:Nn \Paragraph_beforebody:n{#1}
\cs_new_protected:Nn \Paragraph_bodyindent:n{#1}
\cs_new_protected:Nn \Paragraph_afterparagraph:n{#1}
\cs_generate_variant:Nn \__Paragraph_build:nnnnnnnnn {VVVnVVVnV}

% auxiliary function to avoid expansion problems and do some of the formatting
\cs_new_protected:Nn \__Paragraph_build:nnnnnnnnn {
    \Paragraph_beforeparagraph:n { #1 }
    \Aligned{
        \tl_if_empty:nF { #4 }{
            \Paragraph_beforehead:n { #2 }
            \tl_if_empty:nTF { #3 }{\text{#3}}{\parbox{#3}{#4}}
            \Paragraph_afterhead:n { #5 }
        }
        \tl_if_empty:nF { #8 }{
            \Paragraph_beforebody:n { #6 }
            \Paragraph_bodyindent:n { \hspace{#7} }
            { \Aligned{#8} }
        }
    }
    \Paragraph_afterparagraph:n { #9 }
}

% formatting
\NewDocumentCommand{\Paragraph}{
    O{
        beforeparagraph={&},
        beforehead={&},
        width=10cm, 
        afterhead={\\},
        beforebody={&},
        bodyindent=1em,
        afterparagraph={\\}
    } m m
    }{
    \keys_set:nn { Paragraph } { #1 } % populate keys
    % format paragraph
    \__Paragraph_build:VVVnVVVnV
        \l__Paragraph_beforeparagraph_tl
        \l__Paragraph_beforehead_tl
        \l__Paragraph_width_tl
        { #2 }
        \l__Paragraph_afterhead_tl
        \l__Paragraph_beforebody_tl
        \l__Paragraph_bodyindent_tl
        { #3 }
        \l__Paragraph_afterparagraph_tl
}

\ExplSyntaxOff

问题

如何才能改变其中一个值而不改变所有值？

\begin{document}
    \begin{align*}
        \Paragraph{the quick brown fox jumps over the lazy dog the quick brown fox jumps over the lazy dog}{
             2^2 + 3^2
             & = 4 + 9 \\
             & = 13
        } % example with default options
        \Paragraph[width=8cm]{the quick brown fox jumps over the lazy dog the quick brown fox jumps over the lazy dog}{1+1=2} % should overwrite only width; actually overwrites all optional parameters
    \end{align*}
\end{document}

Answer 1

由于不能在的主体周围使用\group_begin:和，因此该方法是在执行时明确给出所需的初始值。\group_end:\Paragraph\keys_set:nn

\documentclass{article}
\usepackage{xparse,amsmath}

\ExplSyntaxOn

\NewDocumentCommand{\Aligned}{O{t} m}
  {
    \begin{aligned}[#1]#2\end{aligned}
  }


% define keys
\keys_define:nn { Paragraph }
  {
    beforeparagraph .tl_set:N  = \l__Paragraph_beforeparagraph_tl,
    beforehead      .tl_set:N  = \l__Paragraph_beforehead_tl,
    width           .tl_set:N  = \l__Paragraph_width_tl,
    afterhead       .tl_set:N  = \l__Paragraph_afterhead_tl,
    beforebody      .tl_set:N  = \l__Paragraph_beforebody_tl,
    bodyindent      .tl_set:N  = \l__Paragraph_bodyindent_tl,
    afterparagraph  .tl_set:N  = \l__Paragraph_afterparagraph_tl,
  }

\cs_new_protected:Nn \Paragraph_beforeparagraph:n{#1}
\cs_new_protected:Nn \Paragraph_beforehead:n{#1}
\cs_new_protected:Nn \Paragraph_width:n{#1}
\cs_new_protected:Nn \Paragraph_afterhead:n{#1}
\cs_new_protected:Nn \Paragraph_beforebody:n{#1}
\cs_new_protected:Nn \Paragraph_bodyindent:n{#1}
\cs_new_protected:Nn \Paragraph_afterparagraph:n{#1}
\cs_generate_variant:Nn \__Paragraph_build:nnnnnnnnn {VVVnVVVnV}

% auxiliary function to avoid expansion problems and do some of the formatting
\cs_new_protected:Nn \__Paragraph_build:nnnnnnnnn
  {
    \Paragraph_beforeparagraph:n { #1 }
    \Aligned
      {
        \tl_if_empty:nF { #4 }
          {
            \Paragraph_beforehead:n { #2 }
            \tl_if_empty:nTF { #3 }{\text{#3}}{\parbox{#3}{#4}}
            \Paragraph_afterhead:n { #5 }
          }
        \tl_if_empty:nF { #8 }
          {
            \Paragraph_beforebody:n { #6 }
            \Paragraph_bodyindent:n { \hspace{#7} }
            { \Aligned{#8} }
          }
      }
    \Paragraph_afterparagraph:n { #9 }
  }

% formatting
\NewDocumentCommand{\Paragraph}{ O{} m m }
  {
    \keys_set:nn { Paragraph }
     {
       beforeparagraph = {&},
       beforehead      = {&},
       width           = 10cm, 
       afterhead       = {\\},
       beforebody      = {&},
       bodyindent      = 1em,
       afterparagraph  = {\\},
       #1
     } % populate keys
    % format paragraph
    \__Paragraph_build:VVVnVVVnV
        \l__Paragraph_beforeparagraph_tl
        \l__Paragraph_beforehead_tl
        \l__Paragraph_width_tl
        { #2 }
        \l__Paragraph_afterhead_tl
        \l__Paragraph_beforebody_tl
        \l__Paragraph_bodyindent_tl
        { #3 }
        \l__Paragraph_afterparagraph_tl
  }

\ExplSyntaxOff

\begin{document}

\begin{align*}
\Paragraph{
  the quick brown fox jumps over the lazy dog the quick 
  brown fox jumps over the lazy dog}{
  2^2 + 3^2
  & = 4 + 9 \\
  & = 13
}
\Paragraph[width=8cm]{
  the quick brown fox jumps over the lazy dog 
  the quick brown fox jumps over the lazy dog}{1+1=2} 
\end{align*}

\end{document}