// Create an optional with an initial value
opt, _ := optional.Of(5)

// An optional created with a nil value returns an error
_, err := optional.Of(nil)

// Create an empty optional
opt := optional.OfEmpty()

var nilPointer *int
_, err := Of(nilPointer) // err is not nil

nilArray := [3]int{}
_, err := Of(nilArray) // err is not nil

var nilSlice []int
_, err := Of(nilSlice) // err is not nil

var nilMap map[int]int
_, err := Of(nilMap) // err is not nil

var nilFunction func()
_, err := Of(nilFunction) // err is not nil

type Point struct {
	x, y int
}
var emptyPoint Point
_, err = Of(emptyPoint) // err is nil

// Get its value and an eventual error if the optional is empty
v, err := opt.Get()

// Get the optional value regardless of its emptiness
v := opt.GetValue()

// Test if the optional is not empty
opt.IsPresent()

// Execute a function if the optional is not empty
opt.IfPresent(f)

// Execute a function if the optional is empty
opt.IfNotPresent(f)

// Returns an error if the optional is not empty (otherwise returns a nil value)
err := opt.IfPresentError(errors.New("present")

// Returns an error if the optional is empty (otherwise returns a nil value)
err := opt.IfNotPresentError(errors.New("not present")

// Panic if the optional is not empty
opt.IfPresentPanic("present")

// Panic if the optional is empty
opt.IfNotPresentPanic("not present")