An alternative introduction to Rust

Post by pjmlp » Sat, Feb 28, 2015, 6:37 AM UTC

pcwalton wrote: post #35

comex wrote: post #24

Earlier quoted context omitted.

This seems like an unfortunate pathological case caused by the abstraction level Rust sits at. The kinds of tree- and graph-like data structures that garbage collected languages can represent in safe code (at the cost of performance) don't work as well in Rust; you can still implement them with various mechanisms (std::swap is very important for trees; Rc and Weak; replacing pointers with indices into a global Vec; e…

This isn't unique to Rust, in fact, as modern C++ presents the same dilemma. Here [1] is a Stack Overflow question where someone asks how to make a doubly-linked list out of smart pointers, and all the answers either involve shared_ptr or C pointers. Same pedagogical issue: you want to deemphasize the less-safe pointers (in Rust, the ones behind an "unsafe" gate; in C++, the raw C pointers) in favor of the safer abst…

Post by MichaelGG » Sat, Feb 28, 2015, 6:40 AM UTC

hackuser wrote: post #44

> Rust’s variable bindings are immutable by default, but can become mutable, allowing them to be re-bound to something else From someone reading about these details for the first time: Calling them variable bindings confuses the matter. You say, just moments earlier, that variables are called by that name because they can change over time, they’re mutable . But this variable is immutable? But only sometimes? ! I know…

Post by MichaelGG » Sat, Feb 28, 2015, 6:45 AM UTC

dbaupp wrote: post #29

Animats wrote: post #13

It's still too confusing. Try drawing actual pictures to illustrate the scope/lifetime issues. Talking about addresses on the stack is an implementation detail. Things to cover: Basic lifetime concepts in Rust: 1. Scopes are nested. 2. Variable lifetimes are tied to scopes. 3. Unlike other languages, variables can be created tied to a scope outer to the one where they are created. The user can control this by indicat…

3. Unlike other languages, variables can be created tied to a scope outer to the one where they are created. The user can control this by indicating that the lifetime of a variable is the same as that of some variable from an outer scope. This is Rust's big innovation. This isn't quite right (or I'm not understanding what you're trying to say). Given let x = 1; { let y = 1; } there's no way you can make `y` itself li…

Post by Animats » Sat, Feb 28, 2015, 7:13 AM UTC

MichaelGG wrote: post #56

dbaupp wrote: post #29

Earlier quoted context omitted.

3. Unlike other languages, variables can be created tied to a scope outer to the one where they are created. The user can control this by indicating that the lifetime of a variable is the same as that of some variable from an outer scope. This is Rust's big innovation. This isn't quite right (or I'm not understanding what you're trying to say). Given let x = 1; { let y = 1; } there's no way you can make `y` itself li…

Regarding the first point, about scope, I'd guess he's referring to lifetimes and how you can explicitly annotate that something can live as long as another thing, like a parameter. Not scope exactly.

Post by progman » Sat, Feb 28, 2015, 8:20 AM UTC

BuckRogers wrote: post #9

I'm a Python user, and always dipping my toes in other tech, working through books on Go, wrote some Node servers and so forth. I rarely find something that has enough advantages to warrant augmenting or replace Python or bring it into 'my stack'. The time involved to really master these things isn't worth it, in my opinion. Something with no GC for hard real-time systems would fit the bill, also something that I cou…