Cons
does not have a special meaning in Rust. It is only the name that the author of the tutorial chose to call that variant of the enum. The same List
could have been defined as:
enum List {
Pair(u32, Box<List>),
Nil
}
The name cons
comes from the Lisp family of programming languages where pairs (nodes of linked lists) are used as the fundamental building blocks of data structures. Here is one way to create the 1,2,3 list in Common Lisp:
(cons 1 (cons 2 (cons 3 nil)))
cons
is a shorthand of construct
by which Lisp programmers mean to allocate memory. Programs that allocate lots of memory are said to be cons
ing too much.