collection by contract

collection.go

type List(type T) []T

func (l *List(T)) Filter(func(T) bool) *List(T)

func (l *List(T)) Map(func(T) T) *List(T)

func main(){
    var l List{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

    l.Filter(func(i int) bool {
	    return i % 2 == 0
    }).Map(func(i int) string{
	    return fmt.Sprintf("No. %d", i)
    })
}