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![package fpinscala.datastructures
sealed trait List[+A]
case object Nil extends List[Nothing]
case class Cons[+A](head: A, tail: List[A]) extends List[A]
object List {
def sum(ints: List[Int]): Int = ints match {
case Nil => 0
case Cons(x,xs) => x + sum(xs)
}
def apply[A](as: A*): List[A] =
if (as.isEmpty) Nil
else Cons(as.head, apply(as.tail: _*))
}
List Cons](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-12-2048.jpg)
![package fpinscala.datastructures
sealed trait List[+A]
case object Nil extends List[Nothing]
case class Cons[+A](head: A, tail: List[A]) extends List[A]
object List {
def sum(ints: List[Int]): Int = ints match {
case Nil => 0
case Cons(x,xs) => x + sum(xs)
}
def apply[A](as: A*): List[A] =
if (as.isEmpty) Nil
else Cons(as.head, apply(as.tail: _*))
}
val x = List(1,2,3,4,5) match {
case Cons(x, Cons(2, Cons(4, _))) => x
case Nil => 42
case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y
case Cons(h, t) => h + sum(t)
case _ => 101
}
List](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-14-2048.jpg)
: List[A]
def dropWhile[A](l: List[A], f: A => Boolean): List[A]](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-20-2048.jpg)
: List[A] =
if (n <= 0) l
else l match {
case Nil => Nil
case Cons(_,t) => drop(t, n-1)
}](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-22-2048.jpg)
: List[A] =
l match {
case Cons(h,t) if f(h) => dropWhile(t, f)
case _ => l
}](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-23-2048.jpg)
(f: (A, B) => B): B](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-26-2048.jpg)
(f: (A, B) => B): B = as match {
case Nil => z
case Cons(x,xs) => f(x, foldRight(xs, z)(f))
}
@annotation.tailrec](https://image.slidesharecdn.com/fpinscala-170513074839/75/FP-in-scala-28-2048.jpg)
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FP in scalaで鍛える関数型脳
- 1. F P inScala x1(井上 ゆり) @iyunoriue unctional rogramming
- 2. $> ? $> ? GPURust WebAssembly & Scala! $> ? ❤ $> GitHub? https://github.com/x1- $> Twitter? @iyunoriue $> URL? http://x1.inkenkun.com/
- 3.
- 4.
- 5.
- 6.
- 7. p.19 We strongly suggestthat you download the exercise source code and do the exercises as you go through each chapter. Exercises, hints, and answers are all available at https://github.com/fpinscala/fpinscla. https://github.com/fpinscala/fpinscla
- 9.
- 10.
- 11.
- 12. package fpinscala.datastructures sealed traitList[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A] object List { def sum(ints: List[Int]): Int = ints match { case Nil => 0 case Cons(x,xs) => x + sum(xs) } def apply[A](as: A*): List[A] = if (as.isEmpty) Nil else Cons(as.head, apply(as.tail: _*)) } List Cons
- 13. val x =List(1,2,3,4,5) match { case Cons(x, Cons(2, Cons(4, _))) => x case Nil => 42 case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y case Cons(h, t) => h + sum(t) case _ => 101 }
- 14. package fpinscala.datastructures sealed traitList[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A] object List { def sum(ints: List[Int]): Int = ints match { case Nil => 0 case Cons(x,xs) => x + sum(xs) } def apply[A](as: A*): List[A] = if (as.isEmpty) Nil else Cons(as.head, apply(as.tail: _*)) } val x = List(1,2,3,4,5) match { case Cons(x, Cons(2, Cons(4, _))) => x case Nil => 42 case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y case Cons(h, t) => h + sum(t) case _ => 101 } List
- 15.
- 16.
- 17. val x =List(1,2,3,4,5) match { case Cons(x, Cons(2, Cons(4, _))) => x case Nil => 42 case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y case Cons(h, t) => h + sum(t) case _ => 101 }
- 18. Q2. drop &dropWhile
- 19. drop dropWhile Q2. drop &dropWhile
- 20. drop dropWhile def drop[A](l: List[A],n: Int): List[A] def dropWhile[A](l: List[A], f: A => Boolean): List[A]
- 21.
- 22. drop def drop[A](l: List[A],n: Int): List[A] = if (n <= 0) l else l match { case Nil => Nil case Cons(_,t) => drop(t, n-1) }
- 23. dropWhile def dropWhile[A]( l: List[A], f:A => Boolean ): List[A] = l match { case Cons(h,t) if f(h) => dropWhile(t, f) case _ => l }
- 24.
- 25.
- 26. foldRight def foldRight[A,B](as: List[A],z: B)(f: (A, B) => B): B
- 27.
- 28. foldRight @annotation.tailrec def foldRight[A,B]( as: List[A],z: B )(f: (A, B) => B): B = as match { case Nil => z case Cons(x,xs) => f(x, foldRight(xs, z)(f)) } @annotation.tailrec
- 29. Functional Programming inScala ❤
- 30. Thank you forlistening!