TL;DR: This behaviour has existed since Python 2.1 PEP 227: Nested Scopes, and was known back then. If a name is assigned to within a class body (like y), then it is assumed to be a local/global variable; if it is not assigned to (x), then it also can potentially point to a closure cell. … Read more
Jeff is right. Note that this is not actually a good test of static scoping (which JS does have). A better one would be: myVar=0; function runMe(){ var myVar = 10; callMe(); } function callMe(){ addMe = myVar+10; } runMe(); alert(addMe); alert(myVar); In a statically scoped language (like JS), that alerts 10, and 0. The … Read more
msg in the except clause is in the same scope as msg on the first line. But in Python 3 we have this new behavior too: When an exception has been assigned using as target, it is cleared at the end of the except clause. This is as if except E as N: foo was … Read more
The short answer is that my marks a variable as private in a lexical scope, and local marks a variable as private in a dynamic scope. It’s easier to understand my, since that creates a local variable in the usual sense. There is a new variable created and it’s accessible only within the enclosing lexical … Read more
I realize there may be beginners looking to organize their code. This is 2022, and if you’re considering a modular JS app, you should get started with npm and Webpack right now. Here are a few simple steps to get started: In your project root, run npm init -y to initialize an npm project Download … Read more
Function hoisting means that functions are moved to the top of their scope. That is, function b() { a = 10; return; function a() {} } will be rewritten by the interpeter to this function b() { function a() {} a = 10; return; } Weird, eh? Also, in this instance, function a() {} behaved … Read more
<<- is most useful in conjunction with closures to maintain state. Here’s a section from a recent paper of mine: A closure is a function written by another function. Closures are so-called because they enclose the environment of the parent function, and can access all variables and parameters in that function. This is useful because … Read more
I understand them through examples. 🙂 First, lexical scope (also called static scope), in C-like syntax: void fun() { int x = 5; void fun2() { printf(“%d”, x); } } Every inner level can access its outer levels. There is another way, called dynamic scope used by the first implementation of Lisp, again in a … Read more