> On Apr 14, 2016, at 4:55 PM, Stephen Canon via swift-evolution
> <[email protected]> wrote:
>
> /// `true` iff the signbit of `self` is set. Implements the IEEE 754
> /// `signbit` operation.
> ///
> /// Note that this is not the same as `self < 0`. In particular, this
> /// property is true for `-0` and some NaNs, both of which compare not
> /// less than zero.
> // TODO: strictly speaking a bit and a bool are slightly different
> // concepts. Is another name more appropriate for this property?
> // `isNegative` is incorrect because of -0 and NaN. `isSignMinus` might
> // be acceptable, but isn't great. `signBit` is the IEEE 754 name.
> var signBit: Bool { get }
>
> init(signBit: Bool, exponent: Int, significand: Self)
These do feel a bit awkward. Perhaps something over-engineered to handle the
typical cases more readably?
public protocol FloatingPoint: SignedArithmetic, Comparable {
enum Sign {
case Plus
case Minus
init(bit: Bool) { return bit ? .Minus : .Plus }
var bit: Bool { get { return self == Minus } }
}
var sign: Sign { get }
var signBit: Bool { get }
init(sign: Sign, exponent: Int, significand: Self)
init(signBit: Bool, exponent: Int, significand: Self)
…
}
…and perhaps each sign/signBit pair would provides one as a default
implementation that calls the other.
Then we can often write something more readable than signBit:
let x = Float(sign: .Plus, exponent: 2, signficand: 2)
if x.sign == .Plus { … }
Alternatively or additionally, perhaps signBit ought to be an Int because the
people writing code using signBit would probably prefer to use literal 1 and 0
instead of true and false. (Hasn't the distinction between Bit and Bool come up
before?)
--
Greg Parker [email protected] Runtime Wrangler
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
