Multiple Returns

A Go function can return more than one value, and that single fact removes a whole category of design from the language. There are no out parameters, no "return -1 for not found and hope nobody stores it", and no exceptions - a function that might not have an answer returns the answer and a bool saying whether it means anything.

func Divide(a, b int) (int, bool) {
	if b == 0 {
		return 0, false
	}
	return a / b, true
}

q, ok := Divide(7, 2)

That shape is called comma-ok, and you will see it everywhere: map lookups, type assertions, channel receives, strings.Cut. When ok is false the other value is the zero value, never a half-answer.

Results can also be named, which declares them as ordinary variables, zeroed on entry:

func MinMax(nums []int) (lo, hi int, ok bool) {
	if len(nums) == 0 {
		return   // 0, 0, false
	}
	...
}

A bare return hands back whatever the named results currently hold. It is worth using for an early exit like that one; a bare return at the end of a long function, where the reader has to scroll to find what is being returned, is not.

Task

Fill in the five functions in main.go.

1. Divide(a, b int) (int, bool) returns a / b, or 0, false when b is zero.
2. MinMax(nums []int) (lo, hi int, ok bool) returns the smallest and largest values. An empty or nil slice is 0, 0, false. It must not reorder its argument.
3. MaxOnly(nums []int) int returns the largest value, or 0 when there is none, by calling MinMax and discarding the minimum.
4. SplitName(full string) (first, last string) splits at the first space: "Grace Brewster Hopper" is "Grace", "Brewster Hopper". A name with no space is all first name.
5. Stats(nums []int) (count, sum int, mean float64) counts, sums and averages. An empty slice returns three zeros and divides nothing.

Hints

• Guard before you divide. Divide and Stats both have to notice the empty case first, because Go panics on integer division by zero rather than giving you an infinity.
• mean is a float64 but sum and count are ints. sum / count is integer division, and converting afterwards - float64(sum / count) - has already thrown the fraction away. Convert both operands, then divide.
• MinMax starts lo and hi at nums[0], not at 0. Starting at zero reports 0 as the minimum of [3 1 4].
• Do not sort the slice to find the ends. sort.Ints would reorder the caller's data, and one test checks that you left it alone.
• _ is the blank identifier: it discards a result. MaxOnly wants _, hi, ok := MinMax(nums), because Go refuses to compile a normal variable that is never read.
• strings.Cut(s, sep) returns before, after, found. It is exactly SplitName, including the no-separator case: before is the whole string and after is empty.