This lesson is applicable to lots of languages, not just Go. For example, lookin...

This lesson is applicable to lots of languages, not just Go. For example, looking at Swift (where the equivalent of an interface is a protocol), we find many protocols in the standard library that either have one function requirement, or add one function requirement to a parent protocol:

- Equatable requires ==

- Comparable extends Equatable, requires <

- Hashable extends Equatable, requires hash(into:)

- Identifiable requires id

- Encodable requires encode(to:)

- Decodable requires init(from:)

- CustomStringConvertible requires description

- LosslessStringConvertible extends CustomStringConvertible, requires init?(_:)

- CustomDebugStringConvertible requires debugDescription

- CaseIterable requires allCases

- Sequence requires makeIterator()

- IteratorProtocol requires next()

- TextOutputStream requires write(_:)

- TextOutputStreamable requires write(to:)

- CustomReflectable requires customMirror

- CustomPlaygroundDisplayConvertible requires playgroundDescription

- AsyncSequence requires makeAsyncIterator()

- AsyncIteratorProtocol requires next()

And Apple’s Swift-only frameworks also have major single-function protocols:

- SwiftUI.View requires body

- SwiftUI.Animatable requires animatableData

- SwiftUI.TimelineSchedule requires entries(from:mode:)

- SwiftUI.EnvironmentKey requires defaultValue

- Combine.Publisher requires receive(subscriber:)

- Combine.Cancellable requires cancel()

- Combine.Subscription requires request(_:)