Questions tagged [lexical-scoping]
48 questions
32
votes
3 answers
Why is `let' faster with lexical scope?
While reading through the source code for the dolist macro, I ran into the following comment.
;; This is not a reliable test, but it does not matter because both semantics are acceptable, tho one is slightly faster with dynamic scoping and the…
Malabarba
- 22,878
- 6
- 78
- 163
18
votes
2 answers
Why do setq and set quote act differently on let-bound variables with lexical scope?
I had a bug in one of my extensions that eventually turned out to be caused by set not working as I expected:
;; -*- lexical-binding: t -*-
(let ((a nil))
(setq a t)
(print a))
(let ((a nil))
(set 'a t)
(print a))
when run with emacs -Q…
dshepherd
- 1,281
- 6
- 18
18
votes
1 answer
Dealing with "Warning: assignment to free variable" when certain libraries can be missing by design
Byte compilation of my mode:
(defun dict-setup-expansions ()
"Add `dict-mode' specific expansions."
(set (make-local-variable 'er/try-expand-list) (list #'dict-mark-article)))
gives warning:
Warning: assignment to free variable…
gavenkoa
- 3,352
- 19
- 36
16
votes
3 answers
Defun inside let with lexical binding gives byte-compile warning "the function is not known to be defined"
I want to get the effect of a static variable by using defun inside of let with lexical binding to create a closure. However, when byte-compiling the file, I get a warning. Am I doing something wrong, or if not, is there a way to suppress this…
Rose Kunkel
- 273
- 1
- 7
13
votes
1 answer
What are the potential pitfalls of enabling lexical-binding for a buffer?
This was inspired by the discussion of lexical-binding vs lexical-let in this question. As lexical-binding gives you the ability to have useful closures people may be used to in other languages like JavaScript why wouldn't you enabled it all the…
stsquad
- 4,626
- 28
- 45
11
votes
1 answer
How is the variable scoping for macros determined?
Take the following example macro, defined in macro.el.
(defmacro some-macro (&rest body)
`(let ((some-variable 1))
,@body))
And take the following function, defined in a different file, function.el.
(defun some-function ()
(some-macro…
Malabarba
- 22,878
- 6
- 78
- 163
10
votes
3 answers
Why does defvar scoping work differently without an initvalue?
Suppose I have a file named elisp-defvar-test.el containing:
;;; elisp-defvar-test.el --- -*- lexical-binding: t -*-
(defvar my-dynamic-var)
(defun f1 (x)
"Should return X."
(let ((my-dynamic-var x))
(f2)))
(defun f2 ()
"Returns the…
Ryan C. Thompson
- 435
- 2
- 10
8
votes
2 answers
'Symbol's value as variable is void' in callback from url-retrieve
When executing the following I get an error:
(defun caller (func)
(url-retrieve "http://m0smith.freeshell.org/"
(lambda (status) (funcall func))))
(caller (lambda() (message "called")))
Result:
error in process filter: Symbol's value as…
M Smith
- 279
- 1
- 7
6
votes
2 answers
Why doesn't "complement" work as a function?
I'm trying to implement the complement function from Common Lisp (CL) in Emacs Lisp, but I'm confused by why defining it as a function (as opposed to a macro) does not work.
The macro definition is straightforward:
(defmacro complement (function)
…
Tianxiang Xiong
- 3,848
- 16
- 27
6
votes
1 answer
Scope in lambda
In my .emacs conf file, I've got this function that adds a hook to set the compile-command based on the mode. It looks something like,
(defun set-compile-cmd (mode-hook cmd)
(add-hook mode-hook (lambda ()
(set (make-local-variable…
user1943733
- 63
- 3
5
votes
2 answers
defun in defun is not local?
I am reading SICP to learn Lisp, the book uses Scheme dialect. I want accommodate it to emacs lisp, I find something weird in 3.1.1 and cannot figure it out, say I have a test.el file:
(defun make-account ()
(defun withdraw (amount)
(print "in…
Alaneuler
- 277
- 1
- 8
5
votes
1 answer
About closure creation
After reading this article about readable closures, I check that:
Since closures are byte-code function objects, they print readably.
You can capture an environment in a closure, serialize it, read it
back in, and evaluate it. That’s pretty…
anquegi
- 739
- 5
- 21
5
votes
1 answer
void-function lexical-let
I'm using this code on Xubuntu (emacs 24.5.1) but it throw error on windows (emacs 25.0.50.1 64bit)
(defun ignore-error-wrapper (fn)
"Funtion return new function that ignore errors.
The function wraps a function with `ignore-errors' macro."
…
jcubic
- 691
- 1
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- 16
4
votes
1 answer
why is a let binding is ignored in compiled function?
I have this function which works perfectly in an uncompiled function. It should let-bind the variable bibtex-completion-bibliography to the result of (org-ref-find-bibliography).
(defun org-ref-valid-keys ()
"Return a list of valid bibtex…
John Kitchin
- 11,555
- 1
- 19
- 41
4
votes
3 answers
idiomatic way to lexically scope variables in a cl-loop body
Here is some asynchronous code in a cl-loop:
;;; foo.el --- -*- lexical-binding: t; -*-
(let ((my-list '(a b c)))
(cl-loop for index below (length my-list)
for value = (seq-elt my-list index)
do…
Damien Cassou
- 877
- 4
- 14