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\catcode`| = 13
\def|{\item {--}}
\def\itemize#1{{\leftskip = 40 pt #1 \par}}

| First item
| Second item

The above example from Latex Wikibook and I do not know what functionality {--} in the itemize provides. Does it have a special meaning?

Also I am confused about the double caret (^^) notation used at the beginning of the Catcodes section such as ^^K for superscript.

In another example there is a nested macro which is added below. It is said that double macro parameters ##n expand to #n, is this always the case?

> %% Required package.

%% TeX function that generates the language commands.
  \ifthenelse{ \equal{\locale}{#1} }{
    \expandafter\def\csname#1\endcsname ##1{##1}
    \expandafter\def\csname#1\endcsname ##1{}

%% Selected language. Can be placed anywhere before the language commands.

%% Language commands.
%% ...

It is good that this page is comprehensive in the sense that a lot of topics are mentioned; however some subtle points are not explained lucidly. I think I should refer to some other source maybe TexBook to better understand the inner workings of TeX. Is there a introductory level short tutorial on TeX that I can use before consulting a more advanced source?

marked as duplicate by David Carlisle tex-core Sep 21 '17 at 22:49

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