Swift3.1(2)Basic Opetators

文档地址：

https://developer.apple.com/library/prerelease/content/documentation/Swift/Conceptual/Swift_Programming_Language/BasicOperators.html#//apple_ref/doc/uid/TP40014097-CH6-ID60

1、swift supports most standard C operators

swfit语言支持大部分c语言的预算符号

2、swift also provides two range operators (a..b and a…b)not found in C

范围符号

3、if the right side of the assignment is a tuple with multiple values,its elements can be decomposed into multiple constants or vairables at once:

let (x,y) = (1,2)

4、Unlike the assignment operator in C and Objective-C ,the assignment operator in swift does not itself return a value.

不像c语言或者oc语言，在swift中的赋值运算符不返回一个值

The following statement is not valid

if x = y {

}

5、arithmetic opetators数学运算符

6、The addition opetater is also supported For String concatnecation.

“hello” + “world”

7、Swift supports all standard C comparison opetators

(==,!=,>)等

8、Swfit also provides two identify operators(=== and !==),which you use to test whether two object references both refer to the same object instance.

用===和！==来测试两个对象指向相同的实例

9、Tuple也能比较，the comparison is already determined by the tuples’ fisrt elements.

如果第一个元素相同，继续看后面的元素

10、Use the ternary conditional operator with care,however.its consiceness can lead to hard-to-read code if overused.Avoid combning multiple instances of the ternary conditional opetator into one compound statement

三元运算符不能滥用，尽量避免将几个三元运算符放进一个复合的语句

11、nil_coalescing Operator

a??b相当于

a != nil ? a! :b

let defaultColorName = “Red”

var userDefinedColorName:String?

var colorNameToUse = userDefinedColorName ??defaultColorName

12、Range Operators

closed Range Operator

range operator(a…b)defines a ranges that runs from a to b, and inludes the values a and b.

for index in 1…5 {

     print(“\(index) times 5 is \(index * 5)”)

}

Half-Open Range Operator

The half-open range operator(a..<b) which does not include b

13、logical Operators

!, && , ||