3 dots in 4 places
Can you name four places where three dots (...) are used in Go?
Variadic function parameters
If the last parameter of a function has type ...T, it can be called with any number of trailing arguments of type T.
The actual type of ...T inside the function is []T.
This example function can be called with, for instance, Sum(1, 2, 3) or Sum().
func Sum(nums ...int) int {
res := 0
for _, n := range nums {
res += n
}
return res
}Arguments to variadic functions
You can pass a slice s directly to a variadic function if you unpack it with the s... notation.
In this case no new slice is created.
In this example, we pass a slice to the Sum function.
primes := []int{2, 3, 5, 7}
fmt.Println(Sum(primes...)) // 17
Array literals
In an array literal, the ... notation specifies
a length equal to the number of elements in the literal.
stooges := [...]string{"Moe", "Larry", "Curly"} // len(stooges) == 3The go command
Three dots are used by the go command as a wildcard when describing package lists.
This command tests all packages in the current directory and its subdirectories.
$ go test ./...Share this page:
