[swift-evolution] The bind thread

Paul Cantrell cantrell at pobox.com
Mon Feb 1 15:52:55 CST 2016

Pulling & updating my comments from the old thread:

> On Feb 1, 2016, at 1:18 PM, Erica Sadun via swift-evolution <swift-evolution at swift.org> wrote:
> The if let x = x {...} and guard let x = x else {...} constructs do something with let (and var) that's fundamentally different from let (and var) elsewhere in the language.

I don’t agree. Wherever they appear, let and var declare a new variable. And they always shadow variables from an outer scope in exactly the same way:

    let x = "hi"
    if 3 < 7 {
        let x = ["different", "scope", "different", "x"]

This consistency of meaning for let/var gives the correct implication: “if let” is just a normal variable declaration, even though it appears in the middle of an if condition.

> The same keywords are used to conditionally unwrap
> and bind an item, not just shadow that item's current value.

In my head, it’s “if”, not “let”, that conveys the conditionality. Really, “if” + “let” is exactly the right combination of concepts; the words just come in a grammatically confusing order.

To me, “bind” misleadingly implies that this is something other than a normal variable declaration: maybe an alias, or a reactive binding, or something like that.



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