Scala：类型不匹配; found：需要的单位：布尔值

Question

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
                 ^

Thanks

Answer 1

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

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

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