Questions tagged [list]

is for the list object in Lisp programming. A list represents a sequence of zero or more elements. Emacs Lisp relies extensively on the list data structure; it is a fundamental building block. Emacs provides many facilities for building, modifying, extending, and efficiently handling list data structures.

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5
votes
0answers
179 views

When to use quote for lists? Modifying quoted lists in Elisp

The Common Lisp Hyper Spec says: The consequences are undefined if literal objects (including quoted objects) are destructively modified. This is further motivated at the Constant Modification ...
3
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1answer
77 views

Does `mapc` place a symbol on the active element of the sequence?

I understand that (eq '(3 . d) '(3 . d)) returns nil, and (eq 3 3) returns t. But I do not understand why delq is deleting one (3 . d) in the second example each loop when y is (3 . d). Is mapc ...
0
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1answer
39 views

The difference between (setq shell t) and (shell . t)

Upon configuring babel, encounter such syntax (require 'ob-ipython) (org-babel-do-load-languages 'org-babel-load-languages '((ipython . t) (python . t) (shell . t) ;; other languages.. )...
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2answers
43 views

Orgmode automatically increment an unordered list

I use org-mode for planning projects and tasks, etc. Say I am reading a book and I want to track my progress chapter by chapter. I want to create a list of repetitive elements with an incremented ...
2
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1answer
51 views

trying to make a self-modifying function [duplicate]

I'm trying to make a function that returns a list of perfect numbers: A perfect number is a positive integer that is equal to the sum of its proper positive divisors For instance, 28 is perfect ...
6
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1answer
126 views

Removing the last element of a list

Is there a simpler way to remove the last element of a list than this? (setq list (reverse (cdr (reverse list))))
6
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1answer
132 views

Shortening trees list with (setcdr (nthcdr 2 trees) nil)

I am starting to learn elisp and working through this tutorial https://www.gnu.org/software/emacs/manual/html_node/eintr/kill_002dnew-function.html and I do not understand this basic example: (setq ...
1
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2answers
393 views

How to continue giving list number after insert a block of code

GNU Emacs 24.5.1 (i686-pc-mingw32) Org-mode version 8.2.10 (release_8.2.10 @ e:/emacs/share/emacs/24.5/lisp/org/) In my org file, 1. one thing #+begin_src sh ls -la #+end_src 2. second ...
1
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1answer
35 views

midnight-mode add-to-list Format specifier doesn't match argument type

I've been trying to get midnight-mode to add to the following list. I have a feeling it has to do with an elisp error in my config I'm not seeing. It works fine with setq, but with add-to-list I get a ...
8
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6answers
5k views

How to remove / delete nth element of a list

Q:  How to remove / delete nth element of a list. CAVEAT:  Do not remove all occurrences / members matching nth element -- e.g., eq or equal. EXAMPLE:  Remove the 17th element of: '(a b c d e f g h ...
2
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1answer
64 views

How to write a list literal with conditional items? [duplicate]

Given a list literal '(1 2 3) is it possible to conditionally include parts of the list? eg: '(1 2 3 (when thing-is-true '(10 11 12))) 4 5 6) Which would result in '(1 2 3 4 5 6) or '(1 2 3 ...
2
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1answer
57 views

Org Mode. Set separation length between elements of a list

I have noticed there is a big gap between the elements of a list when exporting to PDF. Is there a way to modify it?
0
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1answer
42 views

List variable that is set to one list or another depending on condition

I am trying to create a list variable that can be set to one list or another depending on a condition. What I have so far is as follows. (let ((l (if local list1 list2))) ; Append items to the list ...
0
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1answer
44 views

How can i add same value to every item in list, turning it into alist?

I tried to use this code, but it returns (k k k k k) (mapcar (lambda (x) 'cons x '(k)) '(a b c d e)) What am i doing wrong here? Why doesn't cons work?
4
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4answers
253 views

Map function onto nested list?

Q: how can I map a function onto elements of nested lists? For flat lists, we can use mapcar to apply a function to each element of the list: (setq flat '("kittens" "puppies" "otters" "bunnies")) (...
2
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2answers
93 views

Evaluating symbol in function arguments affected by destructive operations?

While evaluating a function call, the arguments is from left to right. For example, (let ((x '(1 2 3))) (list (nreverse x) x)) ;; => ((3 2 1) (1)) The first argument (nreverse x) evaluates to (...
2
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2answers
100 views

Does `car` on an non-lazy function generated list evals the whole list?

I want to get in a huge directory the first file which satisfies some condition, something like (require 'seq) (require 'f) (defun lazy-filter-file (pred path) (car (seq-filter pred (f--files path ...
3
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2answers
108 views

How to delete all list elements matching a regexp?

Given a list: (setq mylist '("a1" "a2" "b1" "b2")) How to delete all elements that match ^a? What I want is "a1" and "a2" deleted, only left "b1" and "b2" in the list.
2
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2answers
38 views

Arbitrary length lists as argument for interactive function

Say I have a defun with a dolist inside that I want to be able to pass a string that is then converted to a list with a length equal to the number of words in said string via the minibuffer, so ...
0
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1answer
26 views

Comparing `system-configuration-options` to a user-specified list

In this example, the system-configuration-options is a string: "--prefix=/Users/HOME/.0.data/.0.emacs/.0.x11 --with-x --with-ns=no --enable-checking=yes,glyphs --enable-check-lisp-object-type --...
0
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1answer
73 views

Updating `dired-directory` after renaming a file

Q:   I have a list of strings: '("apple" "pear" "peach" "nectarine" "watermelon"). How can I replace "peach" with "plum" and maintain the same order of fruits?  [CAVEAT: The list may be very long ...
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0answers
80 views

Directed Acyclic Graphs in Emacs Lisp

Emacs Lisp has support for lists (naturally), association lists, and property lists, vectors, and hash tables. Does it have support for directed acyclic graphs (DAGs)? I have not found a DAG API in ...
1
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1answer
110 views

Replacing autoref command format specification in auctex's font-latex-match-reference-keywords-local

With some help I have redefined the autoref command to take an optional argument, see https://tex.stackexchange.com/questions/428229/autoref-with-optional-argument-text-in-generated-link Now I am ...
6
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2answers
992 views

add-to-list vs add-hook?

What is the difference between add-to-list vs add-hook? For example I see in progmodes/make-mode.el: (add-hook 'completion-at-point-functions #'makefile-completions-at-point nil t) ...
3
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4answers
247 views

How to mapcar uneven lists?

I am aware I can use mapcar to join 2 lists into pairs, however all the map functions seem to quit at the shortest list. This for example (cl-mapcar #'concat '("1" "2" "3" "4") '("a" "b" "c")) ...
2
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2answers
251 views

Sort list by decreasing length of the strings

I have this list: (setq MYLIST '("J. Phys." "New. J. Phys." "J. Phys. Soc. Jap." "Phys. Plasmas")) How can I get a new list ordered by the decreasing ...
2
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2answers
347 views

Adding many items to a list

What is the proper way to add many items to a list? I assume just using many add-to-lists is not the normal way?
0
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1answer
35 views

cons a symbol with a variable and return as a symbol

How can I make fun2 return as the same as fun1? (defun fun1 () '((hello . "test"))) ; <= returns ((hello . "test")) (defun fun2 (str) '((hello . str))) ; <= this is wrong! should return ((...
3
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2answers
52 views

How to define a bundle of variable-and-function pairs?

I want to define a bundle of variable-and-function pairs, e.g.: vl/path-doc points to my often used path, and vl/open-path-doc is used for open it in dired-mode. I tried this piece of code: (setq ...
0
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2answers
250 views

How do I rotate list elements?

Q: how do I rotate the elements of a list such that last becomes first? Given a list of arbitrary length, how do I rotate the list non-destructively such that the last element becomes the first ...
1
vote
1answer
166 views

How to pop an arbitrary element from a list?

Q: how do I pop an arbitrary element from a list? Given the list '(a b c d e), pop returns a and destructively modifies the list to '(b c d e). How can I generalize this function so I could pop an ...
1
vote
1answer
54 views

Doubly-linked list package

Are there any good packages for Emacs that implement doubly-linked lists? I know I could make them myself, but I'd rather not re-invent the wheel.
2
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1answer
308 views

How to sort an association list (alist)?

Is there a way to sort an association list? In my case I would like to sort the alist elements by the values in each list element (represented by the integers in the example below). Example: (setq ...
1
vote
3answers
76 views

How can I convert a list of integers to a string?

Let's say I have a list of integers, representing year, month, day for a date: (2017 8 21) and I want to format the list in one function call, as in (format "%04d-%02d-%02d" 2017 8 21) Is there an ...
1
vote
1answer
47 views

How to create and traverse a multidimensional list

I have code like this: (let* ((l1 '(1 2 3)) (l2 '(4 5 6)) (l3 '(7 8 9)) (ml '(l1 l2 l3))) (dolist (l ml) (message "%s" l) (dolist (e l) (message "%s" e)))) But ...
1
vote
1answer
100 views

How to get the value of :ID: property of a org-contacts-entry in an org-capture-template?

Problem I want to get the value of a property of a org-contacts-db entry: \* Example Contact :MYTAG: :PROPERTIES: :ID: foobar :END: With the function call (org-contacts-filter "Example ...
2
votes
2answers
184 views

Why is the . needed for adding suffixes to the 'auto-mode-alist?

In https://www.emacswiki.org/emacs/AutoModeAlist one needs to use this command in order to add .py for python-mode (add-to-list 'auto-mode-alist '("\\.py\\'" . python-mode)) Why do we need the . ...
0
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1answer
242 views

how to specify an infinite list in lisp?

How to specify a list, which's last element is referring to the first element? By specify I mean, for example, how to write a setq statement with this list. I have seen this in the documentation, ...
2
votes
1answer
1k views

How to enable type-check rules with flycheck-tslint

I want flycheck to use the tslint's --type-check flag to compile my typescript files. In order to see unused imports on the fly inside emacs. By tslint docs --type-check Enables the type ...
13
votes
2answers
6k views

How to concatenate two lists?

Sorry, but elisp is not my best. I need to combine two lists of strings in this way: ("a" "b" "c") + ("d" "e" "f") -> ("a" "b" "c" "d" "e" "f") Well, the order is not important, so I wrote this ...
0
votes
1answer
67 views

Custom function to map through nested lists sorting by time-stamp

In the following example, please assume that we are using time-to-seconds to convert each times-stamp into a decimal representation. I have already converted the time-stamps to seconds in this ...
5
votes
0answers
125 views

Structure-preserving copying of sequences

The form (cl-copy-tree TREE t) returns a deep-copy of a sequence TREE. The the Common Lisp Hyper Spec explains that copy-tree does not preserve circularities and sharing of substructures. I.e., even ...
5
votes
1answer
286 views

Add to a list that defcustom has not yet defined

We can avoid adding duplicate elements to a list variable by using add-to-list. When setting a customizable variable (i.e. one that is or will be defined by defcustom) from our init file, we're ...
6
votes
3answers
398 views

Report duplicates in a list?

Q: how do I get only the duplicate elements in a list? delete-dups (and cl-delete-duplicates) deletes all duplicate elements from a list: (delete-dups '(a b c c d d)) ; => '(a b c d) ...
2
votes
1answer
85 views

Compare all elements of 2 lists, not necessarily in same order

Q: How to test whether all elements of two lists are the same even though the order may be different? EXAMPLE: (test-fn '(answered cached unread) '(unread answered cached)) => t
1
vote
1answer
128 views

Building a list of strings with a regexp while loop

I'd like to perform a regexp search, capture part of a matched string, and save that part to a list. (Eventually the plan is to save this list to a file in a particular format, but for now a simple ...
2
votes
2answers
255 views

Sort list by checked/unchecked state

I was wondering if org-mode offers a function to sort a list by the item states? So that checked items appear on top and unchecked items at the bottom? For example with this list - [ ] Not yet done - ...
3
votes
0answers
229 views

Automatically create checkbox in new line

When creating a list in org-mode, one can press M-RET to create a new line which already has a list item of the same indentation as the line above it in it. How can one achieve the same thing but ...
3
votes
3answers
133 views

List manipulation — appending duplicate equal lists

START WITH: (let ((my-list '((12 1 2016) (12 2 2016) (12 3 2016) (12 1 2016) (12 4 2016) (12 5 2016) ...
0
votes
1answer
103 views

Problems with setting the default font

I'm trying to set the default font for my Emacs based on a variable (so I can use a different font on a different machine): (setq fontspec (concat ck-font-name "-" (number-to-string ck-font-size))) (...