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pgfkeys - .is 系列处理程序

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pgfkeys - .is 系列处理程序

这似乎是一个微不足道的问题，但对于想要理解的人来说鍵盤很好。在以下来自 pgfkeys 包的定义中，为什么不能用\edef替换\def？我之前问过 pgfkeys 大师这个问题，但显然他没有正确理解这个问题，因为我把它与其他问题混在一起了。

\pgfkeys{%
    /handlers/.is family/.code=
    \pgfkeys{\pgfkeyscurrentpath/.ecode=
      \edef\noexpand\pgfkeysdefaultpath{\pgfkeyscurrentpath/}
    }
}

\edef即使将 替换为 ，以下内容仍会给出相同的结果\def。我说得对吗？

\pgfkeys{%
    /handlers/.is family/.code=
    \pgfkeys{\pgfkeyscurrentpath/.ecode=
      \def\noexpand\pgfkeysdefaultpath{\pgfkeyscurrentpath/}
    }
}

\def\firstlayerfam{/fam/subfam}
\def\secondlayerfam{\firstlayerfam}
\def\family{\secondlayerfam}

\pgfkeys{
  \family/.is family,
  \family % This changes the path even without '.cd'. OK!
}

编辑

我看到的原因如下

\long\def\pgfkeys@unpack#1=#2=#3\pgfkeys@stop{%
  \pgfkeys@spdef\pgfkeyscurrentkey{#1}%
   % The following \edef is crucial. In fact, it should come before the last line
   % (ie, before calling the Carlisle despacer \pgfkeys@spdef). Because if #1 is
   % a macro, the content may be the one that carries spurious leading and 
   % trailing spaces. Without expansion, \pgfkeys@add@path@as@needed may even add 
   % default path when it isn't needed. See below.
   \edef\pgfkeyscurrentkey{\pgfkeyscurrentkey}%
   \ifx\pgfkeyscurrentkey\pgfkeys@empty%
    % Skip
  \else
    \pgfkeys@add@path@as@needed
    \pgfkeys@spdef\pgfkeyscurrentvalue{#2}%
    \ifx\pgfkeyscurrentvalue\pgfkeysnovalue@text% Hmm... no value
      \pgfkeysifdefined{\pgfkeyscurrentkey/.@def}%
      {\pgfkeysgetvalue{\pgfkeyscurrentkey/.@def}{\pgfkeyscurrentvalue}}%
      {}% no default, so leave it
    \fi%
    \ifx\pgfkeyscurrentvalue\pgfkeysvaluerequired%
      \pgfkeysvalueof{/errors/value required/.@cmd}%
       \pgfkeyscurrentkey\pgfkeyscurrentvalue\pgfeov%
    \else%
      \pgfkeys@case@one%
    \fi%
  \fi
}

跟踪日志：

{changing \pgfkeyscurrentkey=macro:->\family /.is family}
{into \pgfkeyscurrentkey=macro:->//fam/subfam/.is family}

答案1

很明显（无需使用 pgfkeys）在这种情况下edef和def几乎肯定是相同的。

如果

  \edef\noexpand\pgfkeysdefaultpath{\pgfkeyscurrentpath/}

那么大概没有define \noexpand，而是\noexpand阻止了 的扩展\pgfkeysdefaultpath。这说明整行正在经过扩展上下文（几乎肯定是 edef），如果是 edef，则宏的定义已经扩展前定义，所以\edef和\def会给出相同的结果。

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