Questions tagged [elisp]
*ONLY* for questions about Emacs Lisp as a language, compared to other languages, in particular, compared to other Lisp dialects. That is, it is for questions *about the language* itself. *DO NOT USE IT* for questions about *using* Emacs Lisp, because most questions here are about using Elisp, and adding this tag to them is redundant. Emacs Lisp is the scripting and programming language that the Emacs editor is built on.
415
questions
0
votes
1
answer
45
views
How are markers implemented?
Here is a quote from the Elisp documentation about markers:
A “marker” is a Lisp object used to specify a position in a buffer
relative to the surrounding text. A marker changes its offset from the
...
- 671
0
votes
1
answer
118
views
How to print and read a list to(from) a file?
I'd like to save a (extremely minimal) database made of a lisp list and then read it back.
The list will look like something as follows:
(:foo "bar" :baz "foobar" :foobaz "baz&...
- 103
9
votes
3
answers
479
views
Lambda in `defun` Captures the Lexical Environment, But in `let` It Doesn't
My example is simplified:
(defvar wtf 10)
(defun f (wtf)
(lambda ()
(cl-incf wtf)))
(setq f (f 20))
(setq g (let ((wtf 30))
(lambda ()
(cl-incf wtf))))
(list (funcall f)
...
- 5,578
4
votes
1
answer
659
views
Is it faster to add an element at the beginning of a list with add-to-list than at the end?
I've noticed that some people use a t at the end of this code:
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
that t makes it append at the end of ...
- 451
1
vote
2
answers
235
views
the term “constant” in Elisp
The definition of the term “constant” is clarified in the GNU Emacs Lisp Reference Manual, section 6.2:
For purposes of evaluation, the array is a constant—i.e., it evaluates to itself.
In the ...
- 5,578
7
votes
1
answer
137
views
“(equal a b)⇒t” whereas “(equal b a)⇒error”
GNU Emacs Lisp Reference Manual, 2.8 Equality Predicates:
Comparing circular lists may therefore cause deep recursion that leads to an error, and this may result in counterintuitive behavior such as (...
- 5,578
4
votes
3
answers
298
views
the Term “Hash Notation“ in the Elisp Manual
I'm reading GNU Emacs Lisp Reference Manual, and I see the phrase "hash notation".
Two places in the document seem to have different interpretations, so I have 2 questions.
2.1 Printed ...
- 5,578
4
votes
2
answers
657
views
Is there any function that allows me to execute code on the run?
I'm a Vim user who is trying to migrate to emacs. On Vim, I've been using the following vimscript function to execute code:
function! ExecuteOnTerminal(type) range
if (&ft=='bash' || &ft=='...
- 237
1
vote
0
answers
37
views
Insert output of slow external process in current buffer, character-by-character
Imagine in the current buffer I have the text:
Hello
Bye
I want to call an external program and add the output of it at the end of the buffer. The tricky thing is that the external program provides ...
- 1,786
4
votes
4
answers
5k
views
How can I create block (multiline) comments in Lisp code?
How can I do multiline / block comments in Lisp code - e.g. in the init.el.
In Python I would do it like this
"""Block
comment
"""
In C/C++ like this
/*
Block
comment
*/
...
- 739
1
vote
1
answer
258
views
Validating Arguments to a Function
I would like to validate the argument to a function before its action is executed. The main concern is the passing of a void variable. How can I trap this?
(defun is-it-bound(item)
(if (boundp 'item)...
- 354
1
vote
1
answer
245
views
Does elisp have a way to jump to (goto) labels in the code, ala common lisp's go?
Does elisp have a way to jump to (goto) labels in the code, ala common lisp's go?
(tagbody
(setq val 2)
(go lp)
(incf val 3)
lp (incf val 4)) => NIL
val => 6
PS: This is a ...
- 860
1
vote
1
answer
128
views
Access hash table by value, not key?
Q: how can I access a hash table by its value, not its key?
Association lists can be accessed via either their key or their value:
(setq alist '((a .1) (b . 2) (c . 3)))
(assoc 'a alist) ...
Dan♦
- 33.2k
7
votes
2
answers
1k
views
Underscore in if-let
I often find myself wanting to do something like this:
(if-let* ((foo (get-foo))
(_ (conditionp foo))
(bar (get-bar-from-foo foo)))
...)
As an alternative to:
(let ((foo (get-...
- 492
2
votes
4
answers
1k
views
Equivalent of `continue' in `cl-loop'?
Does the cl-loop macro implement an equivalent to the continue keyword of other languages?
The behavior of break can be achieved by using until or while clauses by placing them in the middle of cl-...
- 1,571