Lexical scoping (sometimes known as static scoping ) is a convention used with many programming languages that sets the scope (range of functionality) of a variable so that it may only be called (referenced) from within the block of code in which it is defined. The scope is determined when the code is compiled. A variable declared in this fashion is sometimes called a private variable.
Questions tagged [lexical-scope]
271 questions
3
votes
2 answers
Ruby Koans - Continuation of Lexical Scope vs Inheritance Hierarchy
I've had a chance to look around in StackOverflow and found this same question which I was trying to better understand from Ruby Koans (Ruby Koans: explicit scoping on a class definition part 2).
class MyAnimals
LEGS = 2
class Bird < Animal
…
wmock
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3
votes
2 answers
Racket: lexical scope inside for
In Haskell, inside a list comprehension, i can bind expressions to a variable every iteration:
[a | x <- xs, let a = x ^ 2, a >= 25]
How do i bind lexical variables in Racket's for comprehension?
Currently i have this code:
(define (euler4)
…
Mirzhan Irkegulov
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3
votes
1 answer
Ambiguous variation of default environment in `getClasses()` (standard function vs. formal S4 method)
I'm having some trouble figuring out what's exactly going on here with respect to "environment nesting"/lexical scoping:
The problem
The default value of argument where in function getClasses() seems to vary depending on whether getClasses() is…
Rappster
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2
votes
5 answers
Why are lexical scopes prefered by the compilers?
How does lexical scope help the compilers? Does it help in compilation or optimization?
unj2
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2
votes
3 answers
JS Scoping issue
Consider the following piece of code:
function processParagraph(paragraph) {
if (paragraph.charAt(0) === '%') {
for (var level = 0; paragraph.charAt(level) === '%'; level++) {}
return {
type: 'h' + level,
…
helpermethod
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2
votes
3 answers
In Ruby, how does one add to an object a method with access to variables in outer scope?
I'm new to Ruby. I'm at the stage where I'm unsuccessfully attempting to write things in Ruby as I would in some other language.
I'm trying to add a method to an object – a humble array, let's say. Not to all arrays, just to one specific one. This…
davidchambers
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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
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- 2
2
votes
2 answers
Rebinding a Subset of Lexical Variables
Given a set of lexical variables, is it feasible to rebind a subset of them depending on circumstances at runtime. My first idea was to use #'set something like:
(let (A B C D E)
(declare (ignorable A B C D E))
(mapc #'set '(b e) (list 1 2)) …
davypough
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2
votes
1 answer
Why does a Dart program behave differently depending on where variables are declared when using lexical scope?
I ran into what seemed like very strange behavior from Dart today. There must be something wrong with how I am understanding local variables and lexical scope. Let's get into some code. The context is a testing grade conversion from numbers to…
Paul Gestwicki
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2
votes
3 answers
Lexical vs Dynamic interpreter in Scheme language
I still do not understand how a dynamic interpreter differ from a lexical one.
I am working on scheme and i find it very difficult to know how a simple code like these one works dynamically and lexically.
(define mystery
(let ((x 2018))
…
Developper zaid
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2
votes
1 answer
Understanding scoping of nested functions
I'm attempting to refactor a script by splitting it into multiple functions, having a main function and "help functions". Here I stumbled upon a problem which can be reduced to the following example:
g <- function(a,b){ # help function
a^2…
maryam
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2
votes
2 answers
Is there a downside to using closures over prototypes?
I like the general style of using closures to create objects with private properties. What I'm unsure of is whether it's more efficient to create the prototype methods within a closure or on the actual prototype of the object. Consider the following…
Frank
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2
votes
1 answer
JS through2 Arrow function this.push()
I have a problem with lexical binding in JavaScript.
This is my code:
.pipe(through.obj((url, enc, done)=>{
if(!url) return done();
request.head(url, (err, response)=>{
this.push(url + ' is ' + (err ? 'down' : 'up') +…
백승훈
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2
votes
2 answers
Should code with trampoline and Y combinator work in lisp with dynamic scope?
I have lisp in javascript which is similar to scheme. It can be used with lexical and dynamic scopes. I was not sure how dynamic scope works and it's seems ok but this code don't work when scope is dynamic:
(define Y
(lambda (h)
((lambda…
jcubic
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2
votes
2 answers
SICP exercise 3.20 - understand the envrionmental diagram (missing binding in my diagram)
There was a question regarding this exercise in this forum, but it dose not answer my specific question. This exercise asks to draw the environmental diagrams for
(define x (cons 1 2))
(define z (cons x x))
(set-car! (cdr z) 17)
(car x)
where cons,…
englealuze
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