package allergies var index = map[string]int{ "eggs": 0x01, "peanuts": 0x02, "shellfish": 0x04, "strawberries": 0x08, "tomatoes": 0x10, "chocolate": 0x20, "pollen": 0x40, "cats": 0x80, } func Allergies(n int) []string { if n <= 0 { return nil } var s []string for k, v := range index { if n&v != 0 { s = append(s, k) } } return s } func AllergicTo(n int, s string) bool { return n > 0 && n&index[s] != 0 }