[swift-evolution] proposal to add "in range" operator

[Preston Sumner]

You can do this:

let testValue = 0.3

// Using instance method.
if (0.0..<1.0).contains(testValue) {
    print("Hello, world.")
}

// Using pattern matching operator.
if 0.0..<1.0 ~= testValue {
    print("Hello, world.")
}

Preston

> On Feb 2, 2016, at 4:53 AM, Gmail 2 via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Hello everyone, 
> I have a proposal to add an "in range” operator in swift.
> 
> ##Current situation
> 
> Checking whether a value is or not within a certain range now depends on the control flow you use. for switch-statement, it is intuitive; but it is not  for if-statement.
> 
> Example:
> 
> let testValue = 0.3
> 
> switch testValue {
> case 0.0..<1.0: do something...
> default: break
> }
> 
> to write the same logic in if-statement, you have to write like this:
> 
> if testValue >= 0.0 && testValue < 1.0 {
>     do something...
> }
> 
> The disadvantage here:
> 1. It’s wordy;
> 2. It’s risky to write the same variable name twice, typo can occur and be ignored;
> 3. It’s inconsistent with switch-statement.
> 
> ##Proposed solution
> 
> Introduce a new operator to check a variable against a range.
> Here is a drafted operator: ~ (infix operator)
> With ~, the above if-statement can be rewritten like:
> 
> if testValue ~ 0.0..<1.0 {
>     do something...
> }
> 
> looks much better.
> 
> What’s more, if combined with the draft proposal Generalized range operators in `for-in`loops and other purposes <https://github.com/apple/swift-evolution/pull/129>, this new operator would more powerful.
> 
> Thanks for reading
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

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