Re: Strange type error

It fails because 

_ + _ * _

is desugared, as you indented, as 

(x,y,z) => x + y * z

but

(_ + _) * _

is desugared as

z => ((x, y) => x + y) * z

You need to use the full form to express what you want.

W dniu czwartek, 7 maja 2015 11:30:29 UTC+2 użytkownik Toby napisał:
>
> Dear Scala Team,
>
> See below for a simple example that uses placeholder syntax, but fails to 
> compile. Essentially, execute accepts a ternary Double operator. In the 
> first example, where the function literal is _ + _ * _ the compile accepts 
> this, but with additional brackets to change precedence, (_ + _) * _ fails.
>
> I'm sure there is a straightforward explanation for this, but I am 
> currently at a lost as to what it is. Any insights would be much 
> appreciated.
>
> Thanks,
>
> Tobias Grasl
>
> object TestTernaryOp {
>
>  
>
>  def execute(fn : (Double, Double, Double) => Double) = {
>
>    fn(1,2,3)
>
>  }
>
>
>   def main( args : Array[String]) =  {
>
>     // Compiles fine
>     println(execute( _ + _ * _ ))
>
>     // Does not compile - type inference error
>     println(execute( (_ + _) * _ ))
>   }
>
> }
>
>
>

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