scala 函数定义使用

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Microsoft Windows [版本 10.0.14393]
(c) 2016 Microsoft Corporation。保留所有权利。

C:\Users\Lenovo>
C:\Users\Lenovo>scala
Welcome to Scala version 2.10.6 (Java HotSpot(TM) Client VM, Java 1.7.0_72).
Type in expressions to have them evaluated.
Type :help for more information.

scala> def ttt(f:Int=>Int){}
ttt: (f: Int => Int)Unit

scala> def ttt(f:Int=>Int){ }
ttt: (f: Int => Int)Unit

scala> def ttt(f:Int=>Int){ println(f(100))}
ttt: (f: Int => Int)Unit

scala>

scala> def ttt(f:Int=>Int){ println(f(100))}
ttt: (f: Int => Int)Unit

scala> val f0 =(x:Int) => x*3
f0: Int => Int = <function1>

scala> ttt(f0)
300

scala> def m1(x:Int) = x * x
m1: (x: Int)Int

scala> ttt(m1(20))
<console>:10: error: type mismatch;
found : Int
required: Int => Int
ttt(m1(20))
^

scala> m1(20)
res2: Int = 400

scala> ttt(m1(20))
<console>:10: error: type mismatch;
found : Int
required: Int => Int
ttt(m1(20))
^

scala> ttt(m1)
10000

scala> def ttt(f:Int=>Int){ println(f(100))}
ttt: (f: Int => Int)Unit

scala> ttt(m1)
10000

scala> m1(3)
res6: Int = 9

scala> m1 _
res7: Int => Int = <function1>

scala> ttt(m1)
10000

scala> ttt(m1(50))
<console>:10: error: type mismatch;
found : Int
required: Int => Int
ttt(m1(50))
^

scala> val f1 = m1 _
f1: Int => Int = <function1>

scala> ttt(f1(50))
<console>:11: error: type mismatch;
found : Int
required: Int => Int
ttt(f1(50))
^

scala> ttt(f1)
10000

scala> ttt(m1 _ )
10000

scala> ttt(x => m1(x) )
10000

scala> ttt(m1)
10000

scala> def m1(x:Int ):Int =x
m1: (x: Int)Int

scala> m1(sss)
<console>:9: error: not found: value sss
m1(sss)
^

scala> m1(555)
res16: Int = 555

scala> def m2(y:Int ):Int =y*y
m2: (y: Int)Int

scala> m2(50)
res17: Int = 2500

scala> def m2(y:Int ) =y*y
m2: (y: Int)Int

scala> def m3y:Int ) =y*y
<console>:1: error: '=' expected but ')' found.
def m3y:Int ) =y*y
^

scala> def m3(y:Int)=y*y
m3: (y: Int)Int

scala> m3(2)
res18: Int = 4

scala> m3(8
| m3(8)
|
|
You typed two blank lines. Starting a new command.

scala>

scala>

scala> m3(8)
res19: Int = 64

scala> val f1 =(x:Int ,y:Int) => x+y
f1: (Int, Int) => Int = <function2>

scala> f1(4,5)
res20: Int = 9

scala> val f2 =(x:Int ,y:Int) =>x*y
f2: (Int, Int) => Int = <function2>

scala> f2(5,5)
res21: Int = 25

scala> def m4(y:Int) = y*y
m4: (y: Int)Int

scala> m4(66)
res22: Int = 4356

scala> val f =m4(y:Int) => y*y
<console>:1: error: not a legal formal parameter
val f =m4(y:Int) => y*y
^

scala> val f =(y:Int) => y*y
f: Int => Int = <function1>

scala> val f4=(y:Int) => y*y
f4: Int => Int = <function1>

scala> f4(5
| f4(5)
|
|
You typed two blank lines. Starting a new command.

scala>

scala>

scala> f4(5)
res23: Int = 25

scala> f4(7
| f4(7)
|
|
You typed two blank lines. Starting a new command.

scala>

scala>

scala>

scala>

scala> f4(7)
res24: Int = 49

scala> f4(8)
res25: Int = 64

scala> (x) =>x
<console>:8: error: missing parameter type
(x) =>x
^

scala> (x:Int) =>x
res27: Int => Int = <function1>

scala> res27(5
|
|
You typed two blank lines. Starting a new command.

scala>

scala>

scala> res27(5)
res28: Int = 5

scala> val arr =Array(1,2,6)
arr: Array[Int] = Array(1, 2, 6)

scala> arr.map(_*10)
res29: Array[Int] = Array(10, 20, 60)

scala> arr.map((x:Int) => x*2)
res30: Array[Int] = Array(2, 4, 12)

scala> (x) =>x
<console>:8: error: missing parameter type
(x) =>x
^

scala> arr.map((x:Int) => x*2)
res32: Array[Int] = Array(2, 4, 12)

scala> arr.map((x) => x*2)
res33: Array[Int] = Array(2, 4, 12)

scala> arr.map((y)=> x*2)
<console>:9: error: not found: value x
arr.map((y)=> x*2)
^

scala>