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\ifcase 突然抱怨“额外 \或”

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\ifcase 突然抱怨“额外 \或”

由于某些奇怪的原因，我有一个\ifcase开始抱怨“额外 \or”但因为\ifcase可以有许多\ors，它怎么会有一个“额外”的呢？

它是一个大包的一部分，相关部分已经工作多年，如下所示。它不再像第二个了\or：

  \ifcase\value{uniquename}%
    \ifuseprefix
      {\usebibmacro{name:family}{#1}{#3}{#5}{}}
      {\usebibmacro{name:family}{#1}{#3}{}{}}%
  \or
     \ifuseprefix
       {\usebibmacro{name:given-family}{#1}{#4}{#5}{}}
       {\usebibmacro{name:given-family}{#1}{#4}{}{}}%
  \or
     \ifuseprefix
       {\usebibmacro{name:given-family}{#1}{#3}{#5}{}}
       {\usebibmacro{name:given-family}{#1}{#3}{}{}}%
  \fi

如果我将第二个更改\or为\else，则会收到“Extra \else”错误。

答案1

问题在于：

\ifdefvoid #1->\ifundef {#1} {\@firstoftwo } {\ifdefmacro {#1} {\ifdefparam {#1} {\@secondoftwo } {\etb@ifdefempty {#1}}} {\@secondoftwo }}
#1<-

\ifundef #1->\ifdefined #1\ifx #1\relax \expandafter \expandafter \expandafter \@firstoftwo \else \expandafter \expandafter \expandafter \@secondoftwo \fi \else \expandafter \@firstoftwo \fi 
#1<-
{\ifdefined: (level 3) entered on line 13}
{true}
{\relax}
{\expandafter}
{\expandafter}
{\else: \ifdefined (level 3) entered on line 13}
{\fi: \ifdefined (level 3) entered on line 13}
{\expandafter}
{\else: \ifcase (level 2) entered on line 13}
{\fi: \ifcase (level 2) entered on line 13}

当\ifdefvoid被调用时，它会被传递一个空参数，因此下一条指令变成

\ifdefined \ifx\relax \expandafter \expandafter \expandafter \@firstoftwo \else \expandafter \expandafter \expandafter \@secondoftwo \fi \else \expandafter \@firstoftwo \fi

并\ifdefined看着\ifx，是已定义，但它也从输入流中移除，因此\fi原本要匹配它的 匹配了外部的\ifcase，如

{\else: \ifcase (level 2) entered on line 13}
{\fi: \ifcase (level 2) entered on line 13}

下一个\or放错了位置。

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