如何在foreach循环中获取索引变量

Question

我有以下 MWE：

\documentclass{article}
\usepackage{pgf, tikz}
\setlength{\parskip}{0.5cm}

\begin{document}
\textbf{Comprehensive knowledge storage follows the evolutionary sequence given by}
\foreach \x in {letter, word, phrase, paragraph, page, book, library} {\x, }
\textbf{while the access to it follows the reverse order.}

\textbf{Keywords:}
\foreach \x in {letter, word, phrase, paragraph, page, book, library} {1.~\x. }

\end{document}

输出如下内容：

在最后一行，不应该出现每个变量的数字1，而应该是一个随着\foreach循环而迭代的索引，就像这样：

所以我的问题是如何获取迭代索引？

谢谢你！

Answer 1

使用count=\n：

\documentclass{article}
\usepackage{pgf, tikz}

\begin{document}
\textbf{Comprehensive knowledge storage follows the evolutionary sequence given by}
\foreach \x in {letter, word, phrase, paragraph, page, book, library} {\x, }% <-----
\textbf{while the access to it follows the reverse order.}

\bigskip

\textbf{Keywords:}
\foreach \x [count=\n] in {letter, word, phrase, paragraph, page, book, library} {\n.~\x. }

\end{document}

我没有尝试修复过满的顶行，但我删除了“library”后的双倍空格。

一个不同的解决方案expl3：第二个参数\uselist是一个模板，其中#1引用索引和#2当前项目。

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn

\NewDocumentCommand{\uselist}{mm}
 {
  \brasil_uselist:nn { #1 } { #2 }
 }

\seq_new:N \l__brasil_uselist_seq
\cs_new:Nn \__brasil_uselist_do:nn { } % initialize

\cs_new_protected:Nn \brasil_uselist:nn
 {
  \cs_set:Nn \__brasil_uselist_do:nn { #2 }
  \seq_set_from_clist:Nn \l__brasil_uselist_seq { #1 }
  \seq_indexed_map_function:NN \l__brasil_uselist_seq \__brasil_uselist_do:nn
 }

\ExplSyntaxOff

\begin{document}

\textbf{Comprehensive knowledge storage follows the evolutionary sequence given by}
\uselist{letter, word, phrase, paragraph, page, book, library}{#2, }%
\textbf{while the access to it follows the reverse order.}

\bigskip

\textbf{Keywords:}
\uselist{letter, word, phrase, paragraph, page, book, library}{#1.~#2. }

\end{document}