「Programming in Scala」の読書、二章

積読のProgramming in Scala消化中...

　流し読みは、２１章辺りまで終ってます。けど流し読みでも後半は読むのがきついので一通り読み終わるのはいつになるのやらｗ；

Chapter 2 First Steps in Scala

Step1. Learn to use the Scala interpreter

replで確認＾＾

scala> 1+2
res1: Int = 3

Java's primitive have corresponding Scala's class.

scala> res1 * 3
res2: Int = 9

これは、知らなかった＊A＊

Step2. Define some variables

scala> val msg = "Hello World!" //=>type inference
msg: java.lang.String = Hello World!

scala> val msg2 : java.lang.String = "Hello again, world!"
msg2: java.lang.String = Hello again, world!

scala> val msg3 : String = "Hello yet again, world!"
msg3: String = Hello yet again, world!

scala> println(msg)
Hello World!

scala> msg = "Goodbye cruel world!"
<console>:5: error: reassignment to val
       msg = "Goodbye cruel world!"

scala> var greeting = "Hello world"
greeting: java.lang.String = Hello world

scala> greeting = "Leave me alone, world!"
greeting: java.lang.String = Leave me alone, world!

Step3. Define some functions

scala> def max(x: Int, y: Int): Int = if(x > y) x else y
max: (Int,Int)Int

scala> def max3(x: Int, y: Int, z: Int): Int = if(x > y && x > z) x else max3(y,z,x)
max3: (Int,Int,Int)Int

scala> max3(1,2,3)
res6: Int = 3

scala> max3(2,3,1)
res7: Int = 3

scala> max3(3,1,2)
res8: Int = 3

paren //=> ()
blanket? //=> []
curly braces //=> {}

scala> def max2(x: Int, y: Int) = if(x>y) x else y
max2: (Int,Int)Int

scala> def greet() = println(msg)
greet: ()Unit

引数なしの戻り値なし

scala> quit

Step4. Write some Scala scripts

Step5. Loop with while; decide with if

配列をindexで操作するのはよろしくないとの事

Step6. INterate with foreach and for

scala> val ary = Array("Concise", "is", "nice")
ary: Array[java.lang.String] = Array(Concise, is, nice)


scala> ary.foreach( a => println(a))           //=>type inference
Concise
is
nice

scala> ary.foreach((a : String) => println(a)) //=>normal
Concise
is
nice

scala> ary.foreach(println(_))                 //=>concise
Concise
is
nice

scala> ary.foreach(println)
Concise
is
nice

forの場合

scala> for(a <- ary)
     | println(a)
Concise
is
nice

conclusion

　scalaの基本を完了っと＾＾；

　う〜ん、まだこの辺は読みやすいんだよね。って後半は多分日本語になっていても理解しづらい部分だからしょうがないけどｗ；

Programming in Scala: A Comprehensive Step-by-step Guide
posted with amazlet at 09.06.28
Martin Odersky Lex Spoon Bill Venners 
Artima Inc 
売り上げランキング: 8148
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