Scala:类型不匹配；找到:所需单位:布尔值 [英] Scala: type mismatch; found : Unit required: Boolean

问题描述

我只是在尝试我的第一批 Scala 并且遇到了这个我不明白的错误.我一直在努力解决这个问题并且已经用尽了我的想法.帮助?

Hi I'm just trying out my first bits of scala and have hit this error which I don't understand. I've been trying to work it out and have exhausted my ideas. Help?

scala> def calculate(count: Int) : Boolean =    
     |           if (count<0) false
<console>:8: error: type mismatch;
 found   : Unit
 required: Boolean
                 if (count<0) false
                 ^

谢谢

推荐答案

你必须有一个 else 子句，否则类型检查器不知道返回类型是什么 不是 count<0 的情况.

You have to have an else clause, otherwise the type checker doesn't know what the return type is when it's not the case that count<0.

def calculate(count: Int): Boolean =    
  if (count<0) false
  else true

或者，更好的是，您根本不需要 if 语句:

Or, better yet, you don't need the if-statement at all:

def calculate(count: Int) = count >= 0

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