Scala映射，zipWithIndex和中缀形式

Question

I have next code:

List.tabulate(n, n)(_ * _).zipWithIndex.map{case (list, index) => index :: list}

I want to write it as suggested by http://docs.scala-lang.org/style/method-invocation.html , so in infix form:

val n = 10
val list = List.tabulate(n, n)(_ * _) zipWithIndex map{case (list, index) => index :: list}

but this stops from compiling. Why? And are there any better explanation when I can use infix and when can I not, rather than a link I gave? It doesn't look like it explains the chained calls of different Arity, like I'm doing

Answer 1

Both zipWithIndex does not take parameters so you cannot write it in infix position. Try:

val n = 10
val list = List.tabulate(n, n)(_ * _).zipWithIndex map { case (list, index) => index :: list }

However, if you meant suffix, that is as Peter mentioned deprecated and discouraged. If you insist though, you would have to import scala.language.postfixOps .

And even then you would not be able to combine suffix with infix notation.

import scala.language.postfixOps
val n = 10
val list = List.tabulate(n, n)(_ * _) zipWithIndex 
val result = list map { case (list, index) => index :: list }