Nine ways to define methods in scala- Nine ways to define a method in Scala?

problem ：

So I've been trying to puzzle through the various ways you can define stuff in Scala, complicated by my lack of understanding of the way {} blocks are treated: therefore , I have been trying to solve your problem in Scala Method of defining content in , And because I am {} The processing of blocks is complicated due to lack of understanding ：

object NewMain extends Thing{    def f1 = 10    def f2 {10}    def f3 = {10}    def f4() = 10    def f5() {10}    def f6() = {10}    def f7 = () => 10    def f8 = () => {10}    def f9 = {() => {10}}    def main(args: Array[String]){        println(f1)     // 10        println(f2)     // ()        println(f3)     // 10        println(f4)     // 10        println(f4())   // 10        println(f5)     // ()        println(f5())   // ()        println(f6)     // 10        println(f6())   // 10        println(f7)     // <function0>        println(f7())   // 10        println(f8)     // <function0>        println(f8())   // 10        println(f9)     // <function0>        println(f9())   // 10    }}

Presumably some of these are equivalent, some of these are syntactic sugar for others, and some are things I should not use, but I can't for the life of me figure it out. Presumably , Some of them are equivalent , Some of them are other people's grammatical sugar , Some things I shouldn't use , But I can't figure it out for my life .My specific questions are: My specific question is ：

• How is it that println(f2) and println(f5()) gives unit ?println(f2) and println(f5()) give unit ？Isn't the last item in the block 10 ? No 10 The last item of the block ？How is it different from println(f3()) , which gives 10 ? It is associated with println(f3()) What's the difference , It gives 10 ？

• If println(f5) gives unit , shouldn't println(f5()) be invalid, since unit is not a function? If println(f5) give unit , Should not be println(f5()) Invalid , because unit Not a function ？The same applies to println(f6) and println(f6()) This also applies to println(f6) and println(f6())

• Of all the ones which print 10: f1 , f3 , f4 , f4() , f6 , f6() , f7() , f8() , f9() , is there any functional difference between them (in terms of what it does) or usage differences (in terms of when I should use which)? Print in all 10： f1 , f3 , f4 , f4() , f6 , f6() , f7() , f8() , f9() , Are there any functional differences between them （ In terms of its function ） ） Or use difference （ In terms of when to use ）？Or are they all equivalent? Or they are all the same ？

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Solution ：

Reference resources ： https://stackoom.com/en/question/YqCX