Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

>Are you saying that Rust will refuse to compile code that does not explicitly

Depends what you mean by explicit.

Look at it like this:

    pub fn main() { 
      let mut vec : Vec<i32> = vec![];
      let x = vec.pop();
      println!("{:?}",x); // prints: None
    }
In this case you see the value is missing.

    vec.pop().expect("I want a value")
will panic with "I want a value" because value is empty. And most rigorous way to deal with it is:

    if let Some(x) = vec.pop() {
       println!("{:?}",x); 
    } else {
       println!("EMPTY"); // prints: Empty
    }
will either print value or EMPTY depending on what the vector contains.

Types like Result will issue warning that you didn't handle the cases.



for some reason I can not answer your subsequent reply so I do it here:

I looked at your example and played a bit with it and yes I agree with you - compiler does help in this case.

My old text:

So instead of checking if vector is not empty you check that the return result is not empty. I do not see much difference. If Rust compiler would choke when "else" clause in your example is not present I would understand your point about compiler preventing improper access.


`x`, the value of the Vector access, only exists within the context of the first block. It does not exist in any other scope. This makes it impossible to access when the result is not valid.

> If Rust compiler would choke when "else" clause in your example is not present

The compiler won't choke, but it will stop you from accessing the value.

It doesn't matter if you omit the `else` clause or not, the type system ensures that you can't access invalid values.

Here's a bit of an example based off of @Ygg2's code: https://play.rust-lang.org/?version=stable&mode=debug&editio...


> for some reason I can not answer your subsequent reply so I do it here

Hacker News will try and discourage really quick back and forth comments. To do so, the reply button is hidden. However, if you click on the timestamp, to go to the comment's own page, you can reply there.


Thanks for the tip. Did not know it




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: