本文将列举Swift常用的内建函数。本文中提到的所谓的内建函数是指那些在Swift中不需要导入任何模块（如Foundation等）或者引用任何类就可以使用的函数。

abs(signedNumber): 返回给定的有符号数字的绝对值

1. abs(-1) //1
2. abs(-42)//42
3. abs(42)//42

1. varlanguages=["Swift","Objective-C"]
2. languages.contains("Swift")//true
3. languages.contains("Java") //false
4. [29,85,42,96,75].contains(42)//true

"Objective-C"]
1. varoldLanguages=dropFirst(languages)
2. print(oldLanguages)//"Objective-C"

 
 

  
  
"Objective-C"]
  
  
varnewLanguages=dropLast(languages)
  
  
print(newLanguages) //"Swift"