Convert a value from one number range into another one. e.g.: 50.remap(from: (min: 0.0, max: 100.0), to: (min: 0.0, max: 1.0)) => 0.5

NumericRemap.swift

protocol Numeric: SignedNumberType
{
    func * (lhs: Self, rhs: Self) -> Self
    func + (lhs: Self, rhs: Self) -> Self
    func - (lhs: Self, rhs: Self) -> Self
    func / (lhs: Self, rhs: Self) -> Self
}

extension Numeric
{
    func remap(from from: (min: Self, max: Self), to: (min: Self, max: Self)) -> Self?
    {
        return remapValue(self, from: (min: from.min, max: from.max), to: (min: to.min, max: to.max))
    }
}

func remapValue <T: Numeric> (input: T, from: (min: T, max: T), to: (min: T, max: T)) -> T?
{
    let div = from.max - from.min
    
    guard div > 0 else
    {
        return nil
    }
    
    return (input - from.min) / div * (to.max - to.min) + to.min
}

extension CGFloat: Numeric {}
extension Float: Numeric {}
extension Double: Numeric {}

// example usage
let a = 0.123.remap(from: (min: 0.0, max: 1.0), to: (min: 100.0, max: 200.0)) // a = 112.3
let b = remapValue(12.0, from: (0.0, 100.0), to: (0.0, 1.0))                  // b = 0.12