I believe the confusion is because you’re conflating names with storage. fn main() { let x = 5; // x_0 println!(“The value of x is {}”, x); let x = 6; // x_1 println!(“The value of x is {}”, x); } In this example, there is one name (x), and two storage locations (x_0 and … Read more
Don’t worry — Go will let you shoot yourself in the foot if you really want to 🙂 Go is not like Erlang, which might be what you are getting at with the question. x := 1 x = 2 allocates one variable, x, with a value of 1, then reassigns it to 2 — … Read more
Instead of creating a brand new type, you can use Ref::map (since Rust 1.8). This has the same result as Levans’ existing answer: use std::cell::Ref; impl Foo { pub fn get_items(&self) -> Ref<‘_, Vec<i32>> { Ref::map(self.interior.borrow(), |mi| &mi.vec) } } You can also use new features like impl Trait to hide the Ref from the … Read more
There are at least two reasons why this is disallowed: You would need to have two concurrent mutable references to map — one held by the iterator used in the for loop and one in the variable map to call map.remove. You have references to the key and the value within the map when trying … Read more
Rand v0.6.0 The Rng::shuffle method is now deprecated; rand::seq::SliceRandom trait should be used. It provides the shuffle() method on all slices, which accepts an Rng instance: // Rust edition 2018 no longer needs extern crate use rand::thread_rng; use rand::seq::SliceRandom; fn main() { let mut vec: Vec<u32> = (0..10).collect(); vec.shuffle(&mut thread_rng()); println!(“{:?}”, vec); } See it … Read more
First a pointed to the string “Dog”. Then you changed the variable a to point at a new string “Dog eats treats”. You didn’t actually mutate the string “Dog”. Strings are immutable, variables can point at whatever they want.
There’s a Moment.js plugin on NPM called frozen-moment – You could use moment().freeze() in place of Object.freeze(moment()). Otherwise, vanilla Moment.js has a clone method that should help you avoid mutability problems, so you could do something like this: var a = moment(), b = a.clone(); // or moment(a) UPDATE: It has been two years since … Read more
As stated in other answers, as of Swift 3 placing var before a variable has been deprecated. Though not stated in other answers is the ability to declare an inout parameter. Think: passing in a pointer. func reduceToZero(_ x: inout Int) { while (x != 0) { x = x-1 } } var a = … Read more