Scala kansai summit-2016

Ad

Ad

Ad

Ad

Ad

Ad

Ad

Ad

Ad

Ad

Ad

Ad

revival
Scala Summit 2016

Scala

Scala ?

•Scala
•
•
Scala ?

•
•
•
•

•
•
•
•

f(x) = x + 1
Scala
• = ( )
•
Which
is
better?
def f(x: Int) {x + 1}
def f(x: Int) = x + 1
def f(x: Int) = return x + 1
※ :...

( )
• (mutable)
•
•

?
int sum = 0;
for (int i = 0; i < array.length; i++) {
sum += array[i];
}
return sum;

i = i + 1;
?

https://goo.gl/iKyEKs

• 1 n
•
int f(int n) {
int total = 0;
for (int i = 1; i <= n; i++) {
total += i;
}
return total;
}

f(1) = 1
f(2) = 1 + 2
f(3) = 1 + 2 + 3
...
f(n) = 1 + 2 + 3 + ... + n

f(1) = 1
f(2) = f(1) + 2
f(3) = f(2) + 3
...
f(n) = f(n - 1) + n
f(1) = 1
f(n) = f(n - 1) + n

def f(n: Int): Int =
if (n == 1) 1
else f(n - 1) + n
f(1) = 1
f(n) = f(n - 1) + n

f(0) = 1
f(1) = 1
f(2) = 2 * 1
f(3) = 3 * 2 * 1
...
f(n) = n * ... * 3 * 2 * 1

f(0) = 1
f(1) = 1 * f(0)
f(2) = 2 * f(1)
f(3) = 3 * f(2)
...
f(n) = n * f(n - 1)

f(0) = 1
f(n) = n * f(n - 1)
def f(n: Int): Int =
if (n == 0) 1
else n * f(n - 1)

n
?
1, 1, 2, 3, 5, 8, 13, …

f(0) = 1
f(1) = 1
f(2) = 1 + 1
f(3) = 1 + 2
f(4) = 2 + 3
f(5) = 3 + 5
...

f(0) = 1
f(1) = 1
f(2) = f(0) + f(1)
f(3) = f(1) + f(2)
f(4) = f(2) + f(3)
f(5) = f(3) + f(4)
...
f(n) = f(n - 2) + f(n - ...

f(0) = 1
f(1) = 1
f(n) = f(n - 2) + f(n - 1)
def f(n: Int): Int =
if (n == 0) 1
else if (n == 1) 1
else f(n - 2) + f(n - 1)

sum
def sum(ints: List[Int]): Int

• Nil
•head tail
head :: tail
3
Nil
Nil::
3 :: Nil2 ::
2 :: 3 :: Nil1 ::
•
•

5 :: 1 :: 2 :: 8 :: Nil
Nil
Nil::8
8 :: Nil::2
2 :: 8 :: Nil::1
1 :: 2 :: 8 :: Nil::5

sum(5 :: 1 :: 2 :: 8 :: Nil)
sum( ) = 0
sum( ) = 8 + 0
sum( ) = 2 + 8 + 0
sum( ) = 1 + 2 + 8 + 0
sum( ) = 5 + 1 + 2 + 8 + ...

sum( ) = 0
sum( ) = + sum( )
sum( ) = + sum( )
sum( ) = + sum( )
sum( ) 
= + sum( )
Nil::8
Nil
8 :: Nil::2
2 :: 8 :: Nil::...

sum( ) = 0
sum( ) = + sum( )
sum( ) = + sum( )
sum( ) = + sum( )
Nil::8
Nil
8 :: Nil::2
2 :: 8 :: Nil::1
Nil8
8 :: Nil2
2 ...

sum(Nil) = 0
sum(head :: tail) = head + sum(tail)
def sum(list: List[Int]): Int =
if (list.isEmpty) 0
else list.head + sum...

def sum(list: List[Int]): Int = list match {
case Nil => 0
case head :: tail => head + sum(tail)
}
def sum(list: List[Int]...

product
def product(ints: List[Int]): Int

max
def max(ints: List[Int]): Int

reverse
def reverse(ints: List[Int]): List[Int]

length
def length(ints: List[Int]): Int

• Functional Programming Principles in Scala 
Scala Martin Odersky
 
https://www.coursera.org/course/progfun
•  
OCaml
 
h...

• Scala & ―
Scalaz
 
2  
http://www.amazon.co.jp/dp/4844337769

Scala kansai summit-2016

Share Slideshare

LinkedIn
Facebook
Twitter

Embed

Size (px)

Show related Slideshows at end

WordPress Shortcode

Link

Share
Email

インターンシップの学生にお届けしようとしたScalaの文法(初級編) by Kentaro Masuda 1677 views
ガチのスタートアップがScalaを採用した結果(公開版) #scala_ks by Kiyotaka Kunihira 1925 views
関数プログラミングことはじめ by Naoki Kitora 1486 views
オンプレミスから AWS への劇的ビフォーアフター by manabusakai 9815 views
Scalaエンジニアのためのモナド入門 by Takashi Imahiro 3929 views
Auktuálne otázky zodpovednosti za p... by Martin Husovec 715 views

View on Slideshare

1 of 47 Ad

View on Slideshare

1 of 47 Ad