ex2

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Exercise 2

Question

Write two functions. The UpdateSlice function takes in a []string and a string. It sets the last position in the passed-in slice to the passed-in string. Print the slice after making the change. The GrowSlice function also takes in a []string and a string. It appends the string onto the slice. Print the slice after making the change. Call these functions from main. Print out the slice before each function is called and after each function is called.

Solution

The logic to update the last element of a slice to a new value isn't difficult, but unlike Python, there's no shortcut built into the language.

func UpdateSlice(s []string, val string) {
	s[len(s)-1] = val
	fmt.Println("in UpdateSlice:", s)
}

func GrowSlice(s []string, val string) {
	s = append(s, val)
	fmt.Println("in GrowSlice:", s)
}

func main() {
	s := []string{"a", "b", "c"}
	UpdateSlice(s, "d")
	fmt.Println("in main after UpdateSlice:", s)
	GrowSlice(s, "e")
	fmt.Println("in main, after GrowSlice:", s)
}

Running this code produces:

$ go build
$ ./ex2 
in UpdateSlice: [a b d]
in main after UpdateSlice: [a b d]
in GrowSlice: [a b d e]
in main, after GrowSlice: [a b d]

You can see how changes to a slice's contents are visible after it is passed to a function, but changes that extend past its length are not.