Scala 関数

• 概要
• 関数の型
• 関数リテラル
• Funtionトレイト
  • メソッド一覧
• 関数オブジェクト
• カリー化
• 部分関数 [/2017-01-29]
  • メソッド一覧

• メソッド定義（def）

scala> var f : ((Int) => Int) = null
f: (Int) => Int = null

scala> var f : (Int => Int) = null
f: (Int) => Int = null

scala> var f : (Int) => Int = null
f: (Int) => Int = null

scala> var f : Int => Int = null
f: (Int) => Int = null

scala> var f : Int => Int = (n:Int)=>{ n+1 }
f: (Int) => Int = <function1>

scala> def test(f:(Int) => Int) = f(123)
test: (f: (Int) => Int)Int

scala> def test(f:Int => Int) = f(123)
test: (f: (Int) => Int)Int

scala> test((n:Int) => { n + 1 })
res51: Int = 124

scala> def foo(n:Int) = n + 1
foo: (n: Int)Int

scala> test(foo)
res52: Int = 124

scala> var f: Int => Long = (n:Int) => n
f: (Int) => Long = <function1>

scala> var f: Function1[Int, Long] = (n:Int) => n
f: (Int) => Long = <function1>

scala> var f: Int=>Long = (n:Int) => n+1
f: (Int) => Long = <function1>

scala> var f: Int=>Long = new Function1[Int, Long] {
     |   def apply(n:Int): Long = n+1
     | }
f: (Int) => Long = <function1>

scala> f(1)
res4: Long = 2

scala> f.apply(1)
res5: Long = 2

scala> f(1)
res6: Long = 2

scala> f.apply(1)
res7: Long = 2

scala> val map = Map("abc"->1, "def"->2, "ghi"->3)
map: scala.collection.immutable.Map[java.lang.String,Int] = Map(abc -> 1, def -> 2, ghi -> 3)

scala> val f: String=>Int = map
f: (String) => Int = Map(abc -> 1, def -> 2, ghi -> 3)

scala> f("abc")
res11: Int = 1

scala> val seq = Seq("abc", "def", "ghi")
seq: Seq[java.lang.String] = List(abc, def, ghi)

scala> val f: Int=>String = seq
f: (Int) => String = List(abc, def, ghi)

scala> f(1)
res12: String = def

scala> val set = Set("abc", "def", "ghi")
set: scala.collection.immutable.Set[java.lang.String] = Set(abc, def, ghi)

scala> val f: String=>Boolean = set
f: (String) => Boolean = Set(abc, def, ghi)

scala> f("abc")
res13: Boolean = true

scala> val arr = Array("abc", "def", "ghi")
arr: Array[java.lang.String] = Array(abc, def, ghi)

scala> val f: Int=>String = arr
f: (Int) => String = WrappedArray(abc, def, ghi)

scala> f(1)
res14: String = def

def func(n: Int): Long = {
  n+1
}

val fp = func _
val fp: Int=>Long = func

printf("%d\n", fp(1))

long func(int n) {
  return n+1;
}

long (*fp)(int) = &func;
long (*fp)(int) = func;

printf("%d\n", fp(1));

def call(f: Int=>Long) = {
  f(123)
}

call(func _)
call(func)

long call(long (*fp)(int)) {
  return fp(123);
}

call(&func);
call(func);

type FP = Int=>Long

val fp2: FP = func

typedef long (*FP)(int);

FP fp2 = func;

scala> def f() = 123
f: ()Int

scala> val g = f
g: Int = 123

scala> val g = f _
g: () => Int = <function0>

def add(a:Int, b:Int) = a+b

val inc: Int=>Int = add(_, 1)
val r = inc(99)

def add(a:Int)(b:Int)(c:Int) = a+b+c

scala> val add1 = add(1) _
add1: (Int) => (Int) => Int = <function1>

scala> add1(2)(3)
res21: Int = 6

scala> val add3 = add(1)(2) _
add3: (Int) => Int = <function1>

scala> add3(4)
res22: Int = 7

scala> def f(a:Int, b:Int) = a+b
f: (a: Int, b: Int)Int

scala> val c = (f _).getClass
c: java.lang.Class[_] = class $anonfun$1

scala> val g = c.newInstance.
     |   asInstanceOf[(Int,Int)=>Int]
g: (Int, Int) => Int = <function2>

scala> g(1,2)
res23: Int = 3

scala> def f(a:Int)(b:Int) = a+b
f: (a: Int)(b: Int)Int

scala> val g = f(1) _
g: (Int) => Int = <function1>

scala> val f = {(a:Int,b:Int)=>a+b}.curried
f: (Int) => (Int) => Int = <function1>

scala> val g = f(1)
g: (Int) => Int = <function1>

scala> val g = f(1)

scala> val g = f(1) _

val pf = new PartialFunction[String, Int] {
  def isDefinedAt(s:String) = s match {
    case "abc" => true
    case "def" => true
    case _ => false
  }
  def apply(s:String): Int = s match {
    case "abc" => 123
    case "def" => 456
  }
}

val s = "abc"
if (pf.isDefinedAt(s)) pf(s) //pf.apply(s)

val pf = {
  case "abc" => 123
  case "def" => 456
}: PartialFunction[String, Int]

val pf: PartialFunction[String, Int] = {
  case "abc" => 123
  case "def" => 456
}

case class Person(name: String, age: Int)

val pf: PartialFunction[Person, Int] = _.name match {
  case "abc" => 123
  case "def" => 456
}

case class Person(name: String, age: Int)

def getName(person: Person) = person.name

val pf: PartialFunction[Person, Int] = person =>
  getName(person) match {
    case "abc" => 123
    case "def" => 456
  }

type =?>[A,B] = PartialFunction[A,B]

val pf: String=?>Int = {
  case "abc" => 123
  case "def" => 456
}