result-struct.swift

public struct Result<Value>
{
  private let state: State<Value>
  
  init(_ value: Value) {
    state = .value(value)
  }

  init(_ error: Error) {
    state = .error(error)
  }

  init(_ f: () throws -> Value) {
    do {
      let value = try f()
      state = .value(value)
    }
    catch {
      state = .error(error)
    }
  }

  public func get() throws -> Value {
    switch state {
    case .value(let value): return value
    case .error(let error): throw error
    }
  }
}

private enum State<Value>
{
  case value(Value)
  case error(Error)
}