Swift integer protocols should include typealias for signedness counterpart
| Originator: | brent | ||
| Number: | rdar://18173851 | Date Originated: | 29-Aug-2014 03:34 AM |
| Status: | Open | Resolved: | |
| Product: | Developer Tools | Product Version: | Xcode6-Beta6 (6A280e) |
| Classification: | Enhancement | Reproducible: | Always |
Summary:
Swift.SignedIntegerType should include an Unsigned typealias, and Swift.UnsignedInteger should include a Signed typealias. This typealias would lead to that type’s same-sized counterpart.
Steps to Reproduce:
1. Write a generic function that takes, say, SignedIntegerType:
func doSomeBitTwiddling <SignedInteger: SignedIntegerType> (x: SignedInteger)
2. Try to make it return a matching unsigned integer:
-> SignedInteger.Unsigned
Expected Results:
You can.
Actual Results:
You can’t. The typealias doesn’t exist.
Notes:
In my case, I’m trying to avoid sign extension during resizing by converting to unsigned before doing certain bit-twiddling operations. This is impossible to do generically.
To that end, SignedIntegerType and UnsignedIntegerType should also include init(bitPattern: Self.Unsigned) or init(bitPattern: Self.Signed).
Comments
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