• Ora
    3·
    3 years ago

    Hey I’m a rust noob. What’s the difference between a const and the default immutable variable?

    • joojmachine
      2·
      3 years ago

      Also noob here (so anyone that knows better can correct me), they have an entire section in The Book dedicated to explaining the differences, but basically those differences are:

      • contants are completely immutable, unlike variables, which are only immutable by default and can be changed using mut;
      • unlike variables, contants can be used in any scope of your code, so if you need some data that needs to be read by many parts of your code, and not just on your main function, it’s way better to use it;
      • since they are constant, as the name suggests, they can only hold expressions or values that can be computed durinig compilation, so for example, it can take an expression like 2.0 * 3.1415 / 4.0 but can’t use variables or other stuff that is processed during runtime, like, x + 14 / y or add(4, 3) (just an example of a function, in this case).