FilterFunc

In the types.go file, we see its definition:

FilterFunc func(string) bool

Looking back at the line in main.go, we see that we use the ByMake filter function:

PrintCars("ByMake - Honda", cars.Filter(ByMake("Honda")))

The ByMake function is defined in the cars.go file:

func ByMake(make string) FilterFunc {
       return func(car string) bool {
              return s.Contains(car, make)
       }
}

The ByMake function is a HOF because it returns a function. Recall that Filter is a HOF because it accepts a function. In this case, ByMake is that function, fn, as we will see in the next section.