[swift-evolution] [pitch] Comparison Reform
clattner at nondot.org
Mon Apr 17 23:40:25 CDT 2017
> On Apr 17, 2017, at 9:07 AM, Joe Groff via swift-evolution <swift-evolution at swift.org> wrote:
>> On Apr 15, 2017, at 9:49 PM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
>> For example, I expect `XCTAssertEqual<T : FloatingPoint>(_:_:)` to be vended as part of XCTest, in order to make sure that `XCTAssertEqual(resultOfComputation, Double.nan)` always fails.
> Unit tests strike me as an example of where you really *don't* want level 1 comparison semantics. If I'm testing the output of an FP operation, I want to be able to test that it produces nan when I expect it to, or that it produces the right zero.
I find it very concerning that == will have different results based on concrete vs generic type parameters. This can only lead to significant confusion down the road. I’m highly concerned about situations where taking a concrete algorithm and generalizing it (with generics) will change its behavior.
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