almostgotcaught 3 days ago

> it shouldn't break fundamental rules of the language

it doesn't? you simply don't understand what a match statement is.

https://doc.rust-lang.org/book/ch19-03-pattern-syntax.html

    let num = Some(4);

    match num {
        Some(x) if x % 2 == 0 => println!("The number {x} is even"),
        Some(x) => println!("The number {x} is odd"),
        None => (),
    }
notice that x is bound to 4.
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  • tialaramex 3 days ago

    Which x? There are two in your code, one for each time you introduce a pattern Some(x) and each x has scope which of course ends when that pattern is done with

    Notice that the Python doesn't work this way, we didn't make a new variable but instead changed the existing one.

    Also, the intent in the Python was a constant, in Rust we'd give this constant an uppercase name by convention, but regardless it's a constant and so of course matching against a constant does what you expect, it can't re-bind a constant, 404 is a constant and so is `const NOT_FOUND: u16 = 404;`

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    • almostgotcaught 3 days ago

      > Which x? There are two in your code, one for each time you introduce a pattern Some(x) and each x has scope which of course ends when that pattern is done with

      if each x's scope ends at the end of each case doesn't that mean there's only one x?

      > we didn't make a new variable but instead changed the existing one.

      so because python doesn't have scopes except for function scopes it shouldn't ever have any new features that intersect with scope?

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      • Spivak 3 days ago

        Also this is pretty much in line for the rest of Python leaving variables around.

            for x in [1]:
      pass
    print(x) # => 1
        The match statement presented is equivalent to an assignment, you do have to know that, but then it's just regular Python.
        Reply View 5 replies
  • pansa2 3 days ago

    > you simply don't understand what a match statement is

    It's "a DSL contrived to look like Python, and to be used inside of Python, but with very different semantics":

    https://discuss.python.org/t/gauging-sentiment-on-pattern-ma...

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    • almostgotcaught 3 days ago

      you linked to a random detractors rant. i don't see what that has to do with whether a match statement binds a match?

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