xs映射（f）和xs之间的差异。 斯卡拉地图（f）

Question

This is a syntax question. I noticed that both of the following produce the same result

(1 until 10) map (square)
(1 until 10) . map (square)

where

def square(x : Int) = x * x

Is there any difference between the two? If so, what?

I did notice that

(1 until 10) map square

works, but

(1 until 10) . map square

is an error (missing arguments for method map in trait TraversableLike; follow this method with `_' if you want to treat it as a partially applied function), but I wasn't quite able to interpret the error message.

Answer 1

You can call a method with infix notation (omitting the dot and the parenthesis) or normally with the dot. If you use normal notation the parentheses are mandatory. See http://docs.scala-lang.org/style/method-invocation.html

Answer 2

Scala offers 2 syntax for invoking methods of arity-1 :

a.m(b)
a m b

Mixing the both is not supported.

Personally, i find that space around the dot make code difficult to read

Answer 3

You could watch Martin Odersky's talk on Scala with style at http://www.parleys.com/play/51c1994ae4b0d38b54f4621b/chapter0/about , he explains the different styles and when (in his opinion) you should use them. Personally I stay away from the space notation for consistency but he thinks it's ok to use it for single expressions, not entire lists of function calls after function calls.

You would use them for operators such as + and - of course.