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The title says it all. I'd like to know what \@car does. I came across it reading through the source of the hyperref package, but it doesn't seem it's defined as part of the package. I tried Google, but there is the sub-string "car" ...

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up vote 17 down vote accepted

In LISP, it returns the first element of a list or a pair. In LaTeX, its definition is \def\@car#1#2\@nil{#1} (defined right before \def\@cdr#1#2\@nil{#2}), and it is defined in LaTeX core (latex.ltx).

The origins of the word come from the architecture of some early IBM computers.

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