如何解决在 Free monad 中使用任一
我正在尝试使用一个作为使用 Free monad 的代数的结果，如下面的代码
///// Command
sealed trait Command[A]
type Result[A] = Either[Exception,A]
object Command {
case class Tell(line: String) extends Command[Result[Unit]]
case class Ask(line: String) extends Command[Result[String]]
}
type App[A] = EitherK[Command,Log,A]
def program(implicit L: logops[App],C: CommandOps[App]): Free[App,Unit] =
for {
_ <- L.show("start <ask>")
name <- C.ask("What's your name?")
_ <- L.show("start <tell>")
_ <- C.tell(s"Hi <$name>,nice to meet you!")
_ <- L.show("done.")
} yield ()
...
L--- start <ask>
What's your name?
George
L--- start <tell>
Hi <Right(George)>,nice to meet you!
L--- done.
有什么想法吗？
谢谢
解决方法
在此链接中找到的解决方案
Scala Free Monads with Coproduct and monad transformer
我必须定义一个像下面这样的函数
{
"Placeholder" : {
"prefix": ","
}
}
并使用它代替 //function to require uncached
function requireUncached(module) {
delete require.cache[require.resolve(module)];
return require(module);
}
//message event callback with prefix
let prefixes = requireUncached('./prefix.json');
let prefix = prefixes['G'+message.guild.id].prefix;
//prefix is now the chosen prefix
//message event callback for new prefix:
//or guildCreate event could use default prefix
let newPre = message.content.split(/ +/)[1];
let prefixes = requireUncached('./prefixes.json');
prefixes['G'+message.guild.id].prefix = newPre
fs.writeFile('./prefixes.json',JSON.stringify(prefixes),err => {
if(err) throw err;
console.log(`Prefix saved as ${newPre}`)
})
//you can modify this for guildCreate event
//so that you won’t get error cannot
//set property prefix of undefined
像下面这样
def liftFE[F[_],T[_],A,B](f: T[Either[A,B]])(implicit I: InjectK[T,F]): EitherT[Free[F,*],B] = EitherT[Free[F,B](Free.liftF(I.inj(f)))
并更改“程序”结果类型
Free.inject版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。