result.ts

'use strict'

export type Result<T, E> = Succ<T> | Fail<E>

export class Succ<T> {
  readonly cont: T
  readonly ok: true = true
  constructor(cont: T) { this.cont = cont }
}

export class Fail<E> {
  readonly err: E
  readonly ok: false = false
  constructor(err: E) { this.err = err }
}

export function isResultSucc<T, E>(result: Result<T, E>): boolean {
  return (result instanceof Succ)
}

export function failResult<T, E>(err: E): Result<T, E> {
  return new Fail(err)
}

export function succResult<T, E>(cont: T): Result<T, E> {
  return new Succ(cont)
}

export function getErr<T, E>(result: Result<T, E>): E {
  if (result instanceof Fail) {
    return result.err
  }
  else {
    throw new Error('不能对一个对的结果使用getErr')
  }
}

export function getCont<T, E>(result: Result<T, E>): T {
  if (result instanceof Succ) {
    return result.cont
  }
  else {
    throw new Error('不能对一个错误的结果使用getCont')
  }
}