Variadic Functions

Variadic Functions

A variadic function accepts a variable number of arguments. You declare one by placing ... before the parameter type:

func sum(nums ...int) int {
    total := 0
    for _, n := range nums {
        total += n
    }
    return total
}

Inside the function, nums is a regular []int slice. You can call it with any number of arguments:

sum(1, 2, 3)    // 6
sum(10, 20)     // 30
sum()           // 0

Passing a Slice with ...

If you already have a slice, you can spread it into a variadic call using ...:

numbers := []int{1, 2, 3, 4}
total := sum(numbers...)

This is the same ... token, but used on the caller side. Without it, the compiler will reject the call --- you cannot pass a slice where individual arguments are expected.

Common Variadic Functions

You have already been using variadic functions. fmt.Println accepts ...any:

fmt.Println("hello", 42, true) // hello 42 true

The built-in append is also variadic --- it appends one or more elements to a slice:

s := []int{1, 2}
s = append(s, 3, 4, 5)

You can even append one slice to another:

a := []int{1, 2}
b := []int{3, 4}
a = append(a, b...)

Rules

• Only the last parameter can be variadic.
• A variadic function can be called with zero arguments for the variadic parameter.
• The variadic parameter is nil (not an empty slice) when no arguments are passed.

Your Task

Write a function joinWithSep that takes a string separator followed by a variadic ...string parameter. It should return a single string with all the strings joined by the separator.

For example: joinWithSep(", ", "a", "b", "c") returns "a, b, c".

If no strings are passed, return an empty string.