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Can’t pass a range to a lambda using Let and Makearray functions

The construct of INDEX() >>:<<INDEX() will work when applied to ranges. Not to arrays AFAIK. It will lead to these errors. Maybe try something like: =LET(range,A1:D2,MAKEARRAY(ROWS(range),COLUMNS(range),LAMBDA(r,c,SUM(INDEX(range,r,SEQUENCE(c)))))) This would resemble the construct of your inital formula. However, in the linked question you have mentioned that you’d like to use SCAN() in combination with BYROW(). You have … Read more

Haskell: Where vs. Let

1: The problem in the example f :: State s a f = State $ \x -> y where y = … x … is the parameter x. Things in the where clause can refer only to the parameters of the function f (there are none) and things in outer scopes. 2: To use a … Read more

Variable scope + eval in Clojure

1.: The reason this doesn’t work is (more or less) given on the page you linked: It is an error if there is no global var named by the symbol […] And: […] A lookup is done in the current namespace to see if there is a mapping from the symbol to a var. If … Read more

Chrome console already declared variables throw undefined reference errors for let

This happens when you introduce the temporal dead zone to the global scope. As you might know, let declarations are hoisted but left uninitialised. Due to control flow, it can happen that a variable is never initialised: function …() { if (false) example; // would throw a ReferenceError if it was evaluated … // do … Read more

In Haskell, when do we use in with let?

Short answer: Use let without in in the body of a do-block, and in the part after the | in a list comprehension. Anywhere else, use let … in …. The keyword let is used in three ways in Haskell. The first form is a let-expression. let variable = expression in expression This can be … Read more

What causes the different behaviors between “var” and “let” when assign them a returned value of a function which throws an error

Declarations of var variables get hoisted – the variable name initialization gets hoisted to the top of the containing function (or, if no function, to the top of the outer block). So var withVar = (function() {throw ‘error!’})() is parsed by the interpreter as var withVar; withVar = (function() {throw ‘error!’})() The same is not … Read more

Confused by the difference between let and let* in Scheme

Let is parallel, (kind of; see below) let* is sequential. Let translates as ((lambda(a b c) … body …) a-value b-value c-value) but let* as ((lambda(a) ((lambda(b) ((lambda(c) … body …) c-value)) b-value)) a-value) and is thus creating nested scope blocks where b-value expression can refer to a, and c-value expression can refer to both … Read more

v8 JavaScript performance implications of const, let, and var?

TL;DR In theory, an unoptimized version of this loop: for (let i = 0; i < 500; ++i) { doSomethingWith(i); } might be slower than an unoptimized version of the same loop with var: for (var i = 0; i < 500; ++i) { doSomethingWith(i); } because a different i variable is created for each … Read more

What is the difference between “let” and “var”?

Scoping rules The main difference is scoping rules. Variables declared by var keyword are scoped to the immediate function body (hence the function scope) while let variables are scoped to the immediate enclosing block denoted by { } (hence the block scope). function run() { var foo = “Foo”; let bar = “Bar”; console.log(foo, bar); … Read more

Why let and var bindings behave differently using setTimeout function? [duplicate]

With var you have a function scope, and only one shared binding for all of your loop iterations – i.e. the i in every setTimeout callback means the same variable that finally is equal to 6 after the loop iteration ends. With let you have a block scope and when used in the for loop … Read more