What is the connection between an empty interface and a regular interface in programming?

In Go, the empty interface interface{} is an interface that contains no methods. It can hold a value of any type because all types implement the empty interface by default. A regular interface, on the other hand, defines a set of methods that a type must implement to satisfy the interface.

Thus, the relationship between the empty and regular interfaces in Go is that the empty interface is a universal container for values of any type, while a regular interface specifies a contract that specific types must fulfill. The empty interface is often used for storing and passing data without a specific type, and regular interfaces are used to define object behavior.

Example:

var any interface{} = 42 // empty interface can hold any value

// Regular interface
type Reader interface {
    Read(p []byte) (n int, err error)
}

// Type implementing Reader
type File struct {}
func (f File) Read(p []byte) (int, error) {
    // implementation
    return 0, nil
}

var r Reader = File{} // File implements Reader