How to write a generic function for floating point values in swift
I want to call floating point methods on floating point types in swift.
func example<T : FloatingPoint>(_ x:T) -> T {
return cos(cbrt(x + 1))
}
Is there a better way to do this than this?
protocol SupportsFloatingPoint : FloatingPoint {
var cubeRoot:Self { get }
var cosine:Self { get }
}
extension Double : SupportsFloatingPoint {
var cubeRoot:Double { return Darwin.cbrt(self) }
var cosine:Double { return Darwin.cos(self) }
}
extension Float : SupportsFloatingPoint {
var cubeRoot:Float { return Darwin.cbrt(self) }
var cosine:Float { return Darwin.cos(self) }
}
func cbrt<T : SupportsFloatingPoint>(_ x:T) -> T {
return x.cubeRoot
}
func cos<T : SupportsFloatingPoint>(_ x:T) -> T {
return x.cosine
}
func example<T : SupportsFloatingPoint>(_ x:T) -> T {
return cos(cbrt(x - 1))
}
Note that the addition operator is lost here. You can use -
, *
and /
, but not +
for SupportsFloatingPoint types.
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You don't need a new protocol. You can extend the existing protocol FloatingPoint
for supported types:
// Just for fun :)
prefix operator √
prefix operator ∛
extension FloatingPoint where Self == Double {
var squareRoot: Self { return sqrt(self) }
var cubeRoot: Self { return cbrt(self) }
var sine: Self { return sin(self) }
var cosine: Self { return cos(self) }
static prefix func √(_ x: Self) -> Self { return x.squareRoot }
static prefix func ∛(_ x: Self) -> Self { return x.cubeRoot }
}
extension FloatingPoint where Self == Float {
var squareRoot: Self { return sqrt(self) }
var cubeRoot: Self { return cbrt(self) }
var sine: Self { return sin(self) }
var cosine: Self { return cos(self) }
static prefix func √(_ x: Self) -> Self { return x.squareRoot }
static prefix func ∛(_ x: Self) -> Self { return x.cubeRoot }
}
print(Double.pi.cosine)
print(√25.0)
print(∛8.0)
Admittedly, there are a lot of code duplicates that I am currently looking into how to minimize. On the bright side, at least this is all static, inline code that will produce very fast machine code.
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