July 2016
Beginner to intermediate
776 pages
17h 26m
Korean
Content preview from 프로그래밍 스칼라: 실용적인 스칼라 활용법을 익히는 가장 확실한 실전 바이블 (2.11.x 버전 기반)
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577
15
장
스칼라 타입 시스템 II
서 온 것이다.
1
이 타입에는 자체 타입 매개변수인
α
가 있다(이 역시 임의로 정한 것이다 ). 이
경우에는
Map
의 값 타입을 지정하기 위해
α
를 사용한다.
➎ 구조적 타입 정의를 끝낸다.
➏ ➋번 줄에서 시작한 식을 끝내면서, 구조적 타입에 있는
λ
에 대한 타입 투영을 사용한다
(
15
.
3
절 ‘타입 투영’을 기억하라).
λ
는 이후에 올 코드에서 추론될 내포된 타입 매개변수를 받
는
Map
에 대한 별명이다.
따라서 타입 람다는
Functor
가 지원하지 못하는,
Map
에 필요한 추가 타입 매개변수를 처리해
준다.
α
는 이어지는 코드에서 추론된다.
λ
나
α
에 대해 명시적으로 다시 참조할 필요는 없다.
다음 스크립트는 이 코드의 동작을 보여준다.
//
src
/
main
/
scala
/
progscala2
/
typesystem
/
typelambdas
/
Functor
.
sc
import scala
.
language
.
higherKinds
import progscala2
.
typesystem
.
typelambdas
.
Functor
.
_
List
(
1
,
2
,
3
)
map2
(
_
*
2
)
//
List
(
2
,
4
,
6
)
Option
(
2
)
map2
(
_
*
2
)
//
Some
(
4
)
val m
=
Map
("
one
"
-
>
1
,
"
two
"
-
>
2
,
"
three
"
-
>
3
)
m map2 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.