Can someone please explain me what is the dot notation in lists:
(first . second)(first second)Whats with the dot notation?
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Re: Whats with the dot notation?
See http://www.gigamonkeys.com/book/they-ca ... ssing.html
It's a Common Lisp book, not an Emacs Lisp book, but I think the concepts more or less apply. Basically (a . b) is called a cons cell -- a is the "car" and b is the "cdr". The cdr tends to be a pointer to another cons cell, making a list. That is, if b is a pointer to (c . d) and d is a pointer to (e . nil), you get (a . (c . (e . nil))), which can be displayed in list form as (a c e). The simple graphics in the link above really help for visualizing what's going on.
It's a Common Lisp book, not an Emacs Lisp book, but I think the concepts more or less apply. Basically (a . b) is called a cons cell -- a is the "car" and b is the "cdr". The cdr tends to be a pointer to another cons cell, making a list. That is, if b is a pointer to (c . d) and d is a pointer to (e . nil), you get (a . (c . (e . nil))), which can be displayed in list form as (a c e). The simple graphics in the link above really help for visualizing what's going on.
Re: Whats with the dot notation?
(cons 'first 'second) ==> (first . second)
(cons 'first (list second)) ==> (first second)Need an online wiki database? My Lisp startup http://www.formlis.com combines a wiki with forms and reports.