Lexical closures are functions, often anonymous, that capture, or close over, their lexical environment. Lexical closures are used extensively in functional programming techniques that involve higher-order functions.
Questions tagged [lexical-closures]
53 questions
3
votes
1 answer
Relationship between the LexicalEnviroment object and [[Enviroment]]
It is told that every block of code has a hidden object called LexicalEnviroment. That object contains a reference to the outer scope and an EnviromentRecord, which contains information about the current scope.
On the other hand, it is said that…
user6898463
3
votes
6 answers
How is this pair of JavaScript functions different?
I’m having a hard time discerning how exactly JavaScript closures work. Please take a look at these two functions and tell how they are different that they produce entirely different results when called multiple times:
Function 1
var add =…
pedroyanky
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- 2
- 10
3
votes
1 answer
Creating a closure around a private function in elisp
In elisp I have the following
(setq lexical-binding t)
(fset 'boom (cl-flet*
((tickle ()
(message "hi"))
(pickle ()
(tickle)))
(lambda ()
…
jacob
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3
votes
3 answers
Differences between Common Lisp and Scheme lexical closures
In Common Lisp I can evaluate the following snippet of code (in SBCL) without being signalled any syntax error:
(let ((x 0))
(defun my-incf (y)
(setf x (+ x y)))
(defun my-decf (y)
(setf x (- x y))))
MY-DECF
CL-USER> (my-incf…
Paulo Tomé
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2
votes
2 answers
JavaScript Closure changing variable value from the outer scope
I don't understand why my returned function didn't change the value of the variable from the outer function.
Hi, I wrote js function:
function num() {
let number = 0;
console.log(number)
return function() {
return number++
…
Sopo1805
- 21
- 2
2
votes
1 answer
Error running timer: (void-variable message) in Emacs init.el
Why do I get Error running timer: (void-variable message)
in the function below in my `init.el - Emacs?
(defun cypher/cowsayx-sclock (in-minutes message)
(interactive "nSet the time from now - min.: \nsWhat: ")
(run-at-time (* in-minutes 60)
…
Achylles
- 31
- 4
2
votes
3 answers
What is in a Python closure and what are the caveats for people used to OCaml?
This is a sort of a follow-up on an old answer to a question about the necessity of functools.partial : while that answer very clearly explains the phenomenon and the basic reason for it, there are still some unclear points to me.
To recap, the…
ysalmon
- 142
- 8
2
votes
4 answers
temporarily overwrite a globally defined function in Scheme let block?
suppose I have the following functions:
(define (g x) (f x))
(define (f x) (+ 1 x))
I would like to temporarily call g with a different f. For example, something like this:
(let ((f (lambda (x) (+ 2 x))))
(g 5))
I would like the code above to…
xdavidliu
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2
votes
3 answers
Identify how the function has been called in closure javascript
Recently i faced one problem in hackerrank which has to calculate multiplication operation and has to return the answer. For example
function multiply(a,b) {
return a*b;
}
Now here is the problem the function might call in different ways such…
Kannan T
- 1,639
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- 29
2
votes
1 answer
OCaml lexical vs dynamic scoping
I have doubts about some topics. In short I have to write an interpreter in Ocaml both static and dynamic scope.
For now I implemented a version with static scoping through the use of an environment (IDE * value) lists, and a eval (evn * exp),…
Jilz
- 31
- 5
2
votes
2 answers
Nested Functions, Closures and Scope
I've been trying to wrap my head around scope, specially closures.
I know that there are many posts about the topic, and I've been reading a lot. But most places refer to the topic as advanced, and use terminology that is relatively difficult to…
Scb
- 339
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2
votes
2 answers
Racket using lexical closures
I read in Let over Lambda about lexical clojures and this code sample was given for Common Lisp:
(let ((counter 0))
(lambda () (incf counter)))
I tried writing this in Racket as:
(let ((counter 0))
(lambda() (+ counter 1)))
When I call it in…
Theodor Berza
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2
votes
1 answer
The nuances of closing over in Javascript
I've been trying to understand the functional composition techniques of Javascript and I came up with his working code of a toy quasi-MVC to demonstrate my question:
var modelFactory = function() {
var _state = false;
var _listener =…
AveryIsDasein
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- 3
2
votes
0 answers
PHP closure functions: why does a closure have to be an anonymous function?
A lambda or anonymous function is just a function without a name.
e.g.
$lambda = function($a, $b) { echo $a + $b; };
A closure is a function which has access to variables not specified
in its parameter list. In PHP 5.3+ these variables are…
John Sonderson
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2
votes
3 answers
Is this scoping possible in javascript?
I am working on a javascript framework. I have several independent scripts that look like this:
core.modules.example_module = function(sandbox){
console.log('wot from constructor ==', wot);
return{
init : function(){
…
kevzettler
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