1.2 变量、常量与内置类型：孵化素材清单

2.2 numintdoubleStringboolListSetMap

2.2 numintdoubleStringboolListSetMap

DartBuilt-in TypesDartDart——

Dart——num``int``double``String``bool``List``Set``Map——

numint double

Dart num int double``num +``-``abs()``compareTo() List<num> List<int> List<double>

int double Dart VMint arbitrary-precision integer Java BigInteger Python int 3264

var large = 1 << 100; // Dart VM127
print(large); //  1267650600228229401496703205376
​

JavaScript Dart JS Dart int JavaScript number IEEE 754 -2^{53} + 1 2^{53} - 1 Number.MAX_SAFE_INTEGER

double IEEE 754 NaN``Infinity Dart float8/

1Dart

“”Dart“”——

Unicode

String DartimmutableUnicodeDart ${expression}

DartUnicode String UTF-16code unitrunesUnicodecharacters characters “‍‍‍” UTF-16surrogate pairs codeUnitAt “” characters.length 1

String family = '‍‍‍';
print(family.length);        // 11UTF-16
print(family.runes.length);  // 7Unicode
print(family.characters.length); // 1
​

Dart

bool

Dart bool true falseJavaScript——“/”truthy/falsyDart bool if (someString) Dart if (someString.isNotEmpty)

“”“”bug

ListSet Map

Dart——List``Set``Map——

List Dart List List<int> checked mode sound null safety [] Dart List List List.unmodifiable const [...]

Set Dart LinkedHashSet``HashSet SplayTreeSet``LinkedHashSet

Map LinkedHashMapPython 3.7+Dart Map Map ——

2Dart

Dart Dart VM int``double``bool “”unboxed int JIT

Dart StringBuffer

final buffer = StringBuffer();
for (var i = 0; i < 1000; i++) {
  buffer.write('item $i, ');
}
String result = buffer.toString();
​

List O(1)/ O(n)Set Map O(1) O(n)SplayTreeSet / O(\log n)“”——

Dart 2.12 Sound Null Safety“” String?``List<int>?“”

String name;
print(name.length); // name 
​

String? name; // 
// 
String name = 'Dart'; // 
​

“”

Dart Dart 3.0 Records

(String, int) userInfo = ('Alice', 30);
var (name, age) = userInfo; // 
​

“”

DartPattern Matching

// 
switch (value) {
  case int i when i > 0: print('');
  case String s when s.isEmpty: print('');
  // ...
}
​

Dart——num String Unicodebool Dart“”“”

WebDartDart

“” Dart