从 Double 列表返回 List[Double]、Map[String, Double]

Question

我正在尝试 return 列表和映射的元组。我已经得到了可以正确编译的列表，但是我不确定如何使用映射和列表来获取与我的列表中的内容匹配的键和值的映射。这是我目前所拥有的：

我已经能够 return列出列表。但是我需要 return (List[Double], Map[String, Double])

    def emulateSingleInstruction(stack: List[Double],
                             env: Map[String, Double],
                             ins: StackMachineInstruction): (List[Double], Map[String, Double]) = {
    ins match{
        case AddI => stack match{
            case i1 :: i2 :: tail => (i1 + i2 :: tail, env)
            case _ => throw new IllegalArgumentException()
        }
        //USE V1 and V2
        case SubI => stack match{
            case i1 :: i2 :: tail => (i1 - i2 :: tail, env)
            case _ => throw new IllegalArgumentException()

        }
        case MultI => stack match{
            case i1 :: i2 :: tail => (i1 * i2 :: tail, env)
            case _ => throw new IllegalArgumentException()
        }
        //USE V1 and V2
        case DivI => stack match{
            case i1 :: i2 :: tail => (i1 / i2 :: tail, env)
            case _ => throw new IllegalArgumentException()
        }
        case ExpI => stack match{
            case Nil => throw new IllegalArgumentException()
            case head :: tail => {
                (scala.math.exp(head) :: tail,env)
            }
        }
        case LogI => stack match{
            case Nil => throw new IllegalArgumentException()
            case head :: tail => {
                if (head > 0){(scala.math.log(head) :: tail,env)}
                else{ throw new IllegalArgumentException()}
            }
        }
        case SinI => stack match{
            case Nil => throw new IllegalArgumentException()
            case head :: tail => {
                (scala.math.sin(head) :: tail,env)
            }
        }
        case CosI => stack match{
            case Nil => throw new IllegalArgumentException()
            case head :: tail => {
                (scala.math.cos(head) :: tail,env)
            }
        }
        case PushI(f) => (f :: stack,env)

        case PopI => stack match{
            case Nil => throw new IllegalArgumentException()
            case i1 :: tail => {
                (tail,env)
            }
        }
    }
}

Answer 1

由于您的示例操作似乎不修改环境而只修改堆栈，我理解您只是在询问如何在 return 值中组合新堆栈和环境。

def emulateSingleInstruction(stack: List[Double],
                             env: Map[String, Double],
                             ins: StackMachineInstruction): (List[Double], Map[String, Double]) = {
    val newStack = ins match {
        case AddI => // your code. Looks good...
    }
    val newEnv = // expression that evaluates to the updated environment
    (newStack, newEnv)
}

从 Double 列表返回 List[Double]、Map[String, Double]

Returning List[Double], Map[String, Double] from a list of Doubles

scala

emulation

pattern-matching