Set a variable to the < ("less than") operator as a function in Swift?

Question

There's a neat guide here about overloading operators in Swift, but it doesn't say anything about treating operators as functions that I can pass around as variables like any other function. I want to do something like var comparator = (<) to set a variable to the < function, but every syntax I've tried hasn't worked, and the Swift Programming Guide doesn't mention anything relevant. I know how to achieve a similar effect with a lambda expression, but that's messy. How can I set a variable to the < function?

Answer 1

If you give comparator an explicit type, then it will work.

var comparator: (Int, Int) -> Bool = (<)

or

var comparator: (Double, Double) -> Bool = (<)

Less than < isn't a single function, but a whole collection of them for different types. By identifying the type you are interested in comparing, you allow the compiler to select the correct less than function.