KeyPath_Sort.swift

prefix func ~<A, B>(_ keyPath: KeyPath<A, B>) -> (A, A) -> Bool where B: Comparable {
    return { $0[keyPath: keyPath] < $1[keyPath: keyPath] }
}

// sort in situ, by name
var p2 = people
p2.sort(by: ~\.name)

// people sorted by name
people.sorted(by: ~\.name)

// people sorted by name in reverse order
people.sorted(by: ~\.name).reversed()

// people sorted by their address city
people.sorted(by: ~\.address.city)

// the names of the people sorted by name
people.sorted(by: ~\.name).map(~\.name)
// => ["Alice", "Bob", "Charles", "Dick", "Harry", "Tom"]