Loop with switch

// Package binarysearch is a small library for finding an element in an ordered sequence
package binarysearch

// SearchInts searches for an element in an ordered sequence and returns its index or -1 if not found
func SearchInts(list []int, key int) int {
	for left, right := 0, len(list); left != right; {
		mid := (left + right) / 2

		switch {
		case list[mid] == key:
			return mid
		case key < list[mid]:
			right = mid
		case key > list[mid]:
			left = mid + 1
		}
	}
	return -1
}

This approach starts by initializing a for loop. The left is initialized to 0 and the right is initialized to the length of the slice of ints passed in. The loop keeps iterating while left does not equal right.

The middle value is set by left plus right divided by 2. For example, if left is 0 and right is 10, then the middle is calculated to 5. if left is 6 and right is 10, then the middle is calculated to 8.

A switch with no condition is used to check the value of the element whose index in the slice of ints is the middle value.

• If the element at the index of the middle value matches the value being searched for, then the middle value is returned.

• If the value being searched for is less than the element at the index of the middle value, then right is set to the middle value so that the next iteration will look at lower numbers.

• Otherwise, the value being searched is greater than the element at the index of the middle value, so left is set to the middle value plus one so that the next iteration will look for higher numbers.

If left and right are changed during the iterations so that they equal other, then the value being searched for is not in the slice of ints. The loop exits and -1 is returned from the function.