• SelfProgrammed@lemmy.today
    link
    fedilink
    English
    arrow-up
    41
    arrow-down
    1
    ·
    11 days ago

    Here’s a secret I wish someone told me in high school: literally everything is pass by value, it’s just that sometimes the value is an address. It demystified pointers for me.

    • ddplf@szmer.info
      link
      fedilink
      arrow-up
      9
      arrow-down
      2
      ·
      edit-2
      11 days ago

      It’s the opposite, everything is passed by reference but primitives are also addresses and therefore passed by value

      You can’t pass objects or functions as value

      • Ephera@lemmy.ml
        link
        fedilink
        English
        arrow-up
        3
        ·
        11 days ago

        I mean, Rust has the additional thing that a reference is a pointer + a borrow, so it’s not quite as similar to a pass-by-value.

        And as for the dereference operator, occasionally you can use it to turn a reference into an owned value, often by making a copy of the value (but in that case, you can usually also use .to_owned()).

        A case where I don’t think there’s an alternative to the dereference operator, is if you’ve got a mutable reference and you want to replace the value that’s underneath: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=04621490e1d0fd6fe1af7f2e843547fb
        At the very least, if you remove the asterisk, the compiler will tell you very precisely that you need to add it back.

    • underisk@lemmy.ml
      link
      fedilink
      arrow-up
      5
      ·
      11 days ago

      They taught you about pointers in high school? The only course available to me that even touched on programming just covered how to use C to do conditionals, read keyboard input, and print text to a terminal. The bulk of the course was learning MS Office.