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@hidelafoglia(lafoglia hide)

Swift vs C# : Strings and Characters

Last updated at Posted at 2014-09-28

String Literals

 26> var a =  "Swift" + 
 27.          "\nMultiline Literal"
a: String = "Swift\nMultiline Literal"
 28> println(a)
Swift
Multiline Literal

csharp> var x = "C#\nLiteral";
csharp> x
"C#
Literal"
csharp> var y = @"C#\nLiteral";
csharp> y
"C#\nLiteral"
csharp> var y = @"C#
      > Literal";
csharp> y
"C#
Literal"

csharp> var a = @"  
      > C# 
      > Multiline
      > Literals
      > "
csharp> a
"
C# 
Multiline
Literals
"

Initializing an Empty String

 29> var s=String()
s: String = ""
 30> s.isEmpty
$R11: Bool = true

csharp> var s="";
csharp> string.IsNullOrEmpty(s);
true

String Mutability

  • ここで言っているのは let の変数は変更出来ないよということでしょう
  • C# : String は immutable, StringBuilderはmutable
  • Objective-C : NSString(immutable), NSMutableString(mutable)
  • Swift: StringはNSString APIにバインドされているようだからimmutableなんじゃないんでしょうか。。。

Strings Are Value Types

Swift:

  • ひょっとして、Stringは実はmutableなのか？
  • 関数呼び出しの際にも "copy-by-default" する
  • "copy-by-default"というのはコピーしないこともある、ということ。オプティマイザがコピーするかしないかを判断する模様

C#:

  • String オブジェクトは、文字列を表す System.Char オブジェクトのシーケンシャル コレクションです。
  • String オブジェクトの値はシーケンシャル コレクションの内容であり、この値は変更できません (つまり、読み取り専用です)。
  • 文字列の不変性に関する詳細については、このトピックの 不変性と Stringbuilder クラス セクションを後で参照します。
  • メモリの String オブジェクトの最大サイズは 2 GB、約 10億文字です。

Working with Characters

  7> for i in "Funkadelic" { print("\(i)-") }; println("")
F-u-n-k-a-d-e-l-i-c-

csharp> foreach(var i in "Funkadelic"){ Console.Write(String.Format("{0}-",i));}; Console.WriteLine();
F-u-n-k-a-d-e-l-i-c-
  • Swift: StringをArrayに変換しないと...
  9> Array("Funkadlic")[0]
$R2: Character = "F"
  • C#: もともと Array of System.Char
csharp> "Funkadelic"[0] 
'F'

Concatenating Strings and Characters

 21> var msg = "Good Morning"
msg: String = "Good Morning"
  • Swift: Character をappendできる(mutable?)
 25> msg.append(Array("!")[0])
 26> msg
$R7: String = "Good Morning!"
  • UnicodeScalarとCharacterはappendできるけど、"!"だとどっちの型かわからん、ということ (> <)
 27> msg.append("!")
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/6778/repl63.swift:2:1: error: ambiguous use of 'append'
msg.append("!")
^
Swift.String:3:17: note: found this candidate
  mutating func append(x: UnicodeScalar)
                ^
Swift.String:7:17: note: found this candidate
  mutating func append(c: Character)
                ^

 27> UnicodeScalar("!")
$R8: (UnicodeScalar) = U+0x00000021 U'!'
 28> msg.append(UnicodeScalar("!"))
 29> msg
$R9: String = "Good Morning!!"
  • C#: String はimmutableなので、追加というのは別途連結したString作成してそれに参照を変えるという事
  • StringBuilderで固定のバッファに処理をできる(mutable)
csharp> var msg = new StringBuilder(100);
csharp> msg.Append("Good Morning")
Good Morning
csharp> msg.Append("!")
Good Morning!
csharp> msg.ToString()
"Good Morning!"

String Interpolation

 30> var x=0, y=1, z=2
x: Int = 0
y: Int = 1
z: Int = 2
 31> "\(x) + \(y) + \(z) = \(x+y+z)"
$R10: String = "0 + 1 + 2 = 3"

 32> func sum(i:Int,j:Int,k:Int)->Int{ return i + j + k }
 33> sum(1,2,3)
$R11: Int = 6

 34> "\(x) + \(y) + \(z) = \(sum(x,y,z))"
$R12: String = "0 + 1 + 2 = 3"

csharp> Func<int,int,int,int> sum = (i,j,k) => { return i + j + k; }
csharp> sum(0,1,2)
3

csharp> var i=0; var j=1; var k=2;
csharp> String.Format("{0} + {1} + {2} = {3}", i,j,k,sum(i,j,k)); 
"0 + 1 + 2 = 3"

Unicode

Unicode Scalars

 40> "\u{0061}"
$R15: String = "a"

 41> "\u{1F496}" 
$R16: String = "?"

csharp> "\u0061"    
"a"
csharp> '\u0061'
'a'

csharp> "\u1f496" 
"Ὁ6"

 42> println("\"Apple\"")
"Apple"

csharp> Console.WriteLine("\"Apple\"");
"Apple"
csharp> Console.WriteLine(@"""Apple""");
"Apple"

Extended Grapheme Clusters

  • 拡張書記素クラスタ

An extended grapheme cluster is a sequence of one or more Unicode scalars that (when combined) produce a single human-readable character.

書記素クラスタ〔grapheme cluster〕は、Unicode文字の列で、ひとつの書記素基底〔grapheme base〕と、付加的な書記素エキステンダ〔grapheme extender〕および/または「前置」文字〔“prepend” character〕から成る。これは人が「文字」とみなすものに近い。

In general, these combinations—surrogate pairs, base characters plus combining marks, Hangul jamo, and Indic consonant clusters—are referred to as grapheme clusters.

Counting Characters

 43> countElements("Supergroovalisticprosifunkstication")
$R17: Int = 35

csharp> "Supergroovalisticprosifunkstication".Length
35

Comparing Strings

String and Character Equality

  • Swift : == , != 
csharp> var a = "Funky"
csharp> var b = "Funky"
csharp> a == b
true
csharp> a != b
false
csharp> a.CompareTo(b)
0
csharp> string.CompareOrdinal(a,b)
0
csharp> a.SequenceEqual(b)
true

Prefix and Suffix Equality

 44> "Act 2 Scene 2: Capulet's orchard".hasPrefix("Act 2")
$R18: Bool = true

 45> "Act 2 Scene 2: Capulet's orchard".hasSuffix("orchard") 
$R19: Bool = true

csharp> "Act 2 Scene 2: Capulet's orchard".StartsWith("Act 2")
true

csharp> "Act 2 Scene 2: Capulet's orchard".EndsWith("orchard") 
true

Unicode Representations of Strings

UTF-8, UTF-16 Representation

 46> "Supergroovalisticprosifunkstication".utf8
$R20: String.UTF8View = {
  _core = {
    _baseAddress = 0x0000000102876b60
    _countAndFlags = 9223372036854775843
    _owner = nil
  }
}
 47> "Supergroovalisticprosifunkstication".utf16
$R21: String.UTF16View = {
  _offset = 0
  _length = 35
  _core = {
    _baseAddress = 0x0000000102876d60
    _countAndFlags = 9223372036854775843
    _owner = nil
  }
}

csharp> System.Text.Encoding.UTF8.GetBytes("Supergroovalisticprosifunkstication")
{ 83, 117, 112, 101, 114, 103, 114, 111, 111, 118, 97, 108, 105, 115, 116, 105, 99, 112, 114, 111, 115, 105, 102, 117, 110, 107, 115, 116, 105, 99, 97, 116, 105, 111, 110 }

csharp> System.Text.Encoding.GetEncoding("UTF-16").GetBytes("Supergroovalisticprosifunkstication")
{ 83, 0, 117, 0, 112, 0, 101, 0, 114, 0, 103, 0, 114, 0, 111, 0, 111, 0, 118, 0, 97, 0, 108, 0, 105, 0, 115, 0, 116, 0, 105, 0, 99, 0, 112, 0, 114, 0, 111, 0, 115, 0, 105, 0, 102, 0, 117, 0, 110, 0, 107, 0, 115, 0, 116, 0, 105, 0, 99, 0, 97, 0, 116, 0, 105, 0, 111, 0, 110, 0 }

Unicode Scalar Representation

 49> "Supergroovalisticprosifunkstication".unicodeScalars
$R23: String.UnicodeScalarView = {
  _core = {
    _baseAddress = 0x00000001028791b0
    _countAndFlags = 9223372036854775843
    _owner = nil
  }
}

 51> for i in "Supergroovalisticprosifunkstication".unicodeScalars { print("\(i.value)-")} ; println(""); 
83-117-112-101-114-103-114-111-111-118-97-108-105-115-116-105-99-112-114-111-115-105-102-117-110-107-115-116-105-99-97-116-105-111-110-


csharp> System.Text.Encoding.UTF8.GetBytes("Supergroovalisticprosifunkstication")
{ 83, 117, 112, 101, 114, 103, 114, 111, 111, 118, 97, 108, 105, 115, 116, 105, 99, 112, 114, 111, 115, 105, 102, 117, 110, 107, 115, 116, 105, 99, 97, 116, 105, 111, 110 }

csharp> foreach(var i in "Supergroovalisticprosifunkstication"){ Console.Write(string.Format("{0}-",(byte)i));}
83-117-112-101-114-103-114-111-111-118-97-108-105-115-116-105-99-112-114-111-115-105-102-117-110-107-115-116-105-99-97-116-105-111-110-
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