=>在Scala中意义是什么，看到很多这样的符号
=>在Scala中意义是什么，看到很多这样的符号
j = 0
val s2 = s.split(",").filter(_.trim.nonEmpty).foreach {
item =>
{
j = j + 1
println(item, j)
}
}
=> has several meanings in Scala, all related to its mathematical meaning as implication.
1. In a value, it introduces a function literal, or lambda. e.g. the bit inside the curly braces inList(1,2,3).map { (x: Int) => x * 2 }
2. In a type, with symbols on both sides of the arrow (e.g. A => T, (A,B) => T, (A,B,C) => T, etc.) it's sugar forFunction<n>,T], that is, a function that takes parameters of typeA[,B...], and returns a value of type T.
2.1Empty parens on the left hand side (e.g. () => T) indicate that the function takes no parameters (also sometimes called a "thunk");
2.2 Empty parens on the right hand side denote that it returns ()—the sole value of type Unit, whose name can also be written ()—confused yet? :)
A function that returns Unit is also known as a procedure, normally a method that's called only for its side effect.
3. In the type declaration for a method or function parameter, with no symbol on the left hand side (e.g.def f(param: => T)) it's a "by-name parameter", meaning that is evaluated every time it's used within the body of the function, and not before. Ordinary "by-value" parameters are evaluated before entry into the function/method.
4.In a case clause, they separate the pattern (and optional guard) from the result expression, e.g.case x => y.
怎么不翻译一下呢？ 271592448 发表于 2015-3-13 09:37
怎么不翻译一下呢？
Scala 支持定义匿名函数，匿名函数由参数列表，箭头连接符（ =>）和函数体组成
// 定义匿名函数
val cube = (x: Int) => x * x *x
x * x *x 是函数体
(x: Int)是匿名函数的参数
=>连接参数列表和函数体
参考：Scala 初级入门3：简洁的 Scala 语法
Scala 支持定义匿名函数，匿名函数由参数列表，箭头连接符（ =>）和函数体组成
// 定义匿名函数
val cube = (x: Int) => x * x *x
x * x *x 是函数体
(x: Int)是匿名函数的参数
=>连接参数列表和函数体
参考：Scala 初级入门3：简洁的 Scala 语法
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