Scala中VAL的范围界定规则是什么
当我在a中使用val进行理解时,我得到警告: 警告:用于理解的val关键字已弃用 尽管规范的语法附录中有产品 这意味着当我做类似的事情时Scala中VAL的范围界定规则是什么,scala,for-comprehension,Scala,For Comprehension,当我在a中使用val进行理解时,我得到警告: 警告:用于理解的val关键字已弃用 尽管规范的语法附录中有产品 这意味着当我做类似的事情时 for (x <- xs; a = x) for (x <- xs) yield { implicit val a = x; /* more */ } for(x就像普通的val pat=expr定义一样,等号左边的东西只是一个模式 语法规范中的枚举器结果显示for expr中的子句可以是生成器(def bar(隐式i:Int)=Some(i+
for (x <- xs; a = x)
for (x <- xs) yield { implicit val a = x; /* more */ }
for(x就像普通的val pat=expr
定义一样,等号左边的东西只是一个模式
语法规范中的枚举器结果显示for expr中的子句可以是生成器(def bar(隐式i:Int)=Some(i+1)
scala>隐式变量imp:Int=0
scala>用于{a
// yucky, yet instructive
scala> val xs = List(1,2,3)
scala> def bar(implicit i: Int) = Some(i+1)
scala> implicit var imp: Int = 0
scala> for { a<-xs; if { imp=a; true }; b<-bar } yield b
res6: List[Int] = List(2, 3, 4)
tmp <- xs
a = f(tmp) // some arbitrary function of tmp
// amounts to
(tmp, a) <- for (x@tmp <- xs) yield { val x0@a=f(tmp); (x, x0) }
scala> def f(vs: List[Int]) = for (a <- vs; b = a+1) yield b
f: (vs: List[Int])List[Int]
scala> :javap f
[snip]
public scala.collection.immutable.List<java.lang.Object> f(scala.collection.immutable.List<java.lang.Object>);
flags: ACC_PUBLIC
Code:
stack=3, locals=2, args_size=2
0: aload_1
1: new #16 // class $anonfun$f$1
4: dup
5: invokespecial #17 // Method $anonfun$f$1."<init>":()V
8: getstatic #22 // Field scala/collection/immutable/List$.MODULE$:Lscala/collection/immutable/List$;
11: invokevirtual #26 // Method scala/collection/immutable/List$.canBuildFrom:()Lscala/collection/generic/CanBuildFrom;
14: invokeinterface #32, 3 // InterfaceMethod scala/collection/TraversableLike.map:(Lscala/Function1;Lscala/collection/generic/CanBuildFrom;)Ljava/lang/Object;
19: checkcast #28 // class scala/collection/TraversableLike
22: new #34 // class $anonfun$f$2
25: dup
26: invokespecial #35 // Method $anonfun$f$2."<init>":()V
29: getstatic #22 // Field scala/collection/immutable/List$.MODULE$:Lscala/collection/immutable/List$;
32: invokevirtual #26 // Method scala/collection/immutable/List$.canBuildFrom:()Lscala/collection/generic/CanBuildFrom;
35: invokeinterface #32, 3 // InterfaceMethod scala/collection/TraversableLike.map:(Lscala/Function1;Lscala/collection/generic/CanBuildFrom;)Ljava/lang/Object;
40: checkcast #37 // class scala/collection/immutable/List
43: areturn