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📜  Swift-运算符

📅  最后修改于: 2020-12-25 04:26:37             🧑  作者: Mango

运算符是一个符号，告诉编译器执行特定的数学或逻辑操作。 Objective-C包含丰富的内置运算符，并提供以下类型的运算符-

  • 算术运算符
  • 比较运算符
  • 逻辑运算符
  • 按位运算符
  • 赋值运算符
  • 范围运算符
  • 杂项运算符

本教程将逐一说明算术，关系，逻辑，按位，赋值和其他运算符。

算术运算符

下表显示了Swift 4语言支持的所有算术运算运算符。假设变量A持有10，变量B持有20，则-

Operator Description Example
+ Adds two operands A + B will give 30
− Subtracts second operand from the first A − B will give -10
* Multiplies both operands A * B will give 200
/ Divides numerator by denominator B / A will give 2
% Modulus Operator and remainder of after an integer/float division B % A will give 0

比较运算符

下表显示了Swift 4语言支持的所有关系运算符。假设变量A持有10，变量B持有20，则-

Operator Description Example
== Checks if the values of two operands are equal or not; if yes, then the condition becomes true. (A == B) is not true.
!= Checks if the values of two operands are equal or not; if values are not equal, then the condition becomes true. (A != B) is true.
> Checks if the value of left operand is greater than the value of right operand; if yes, then the condition becomes true. (A > B) is not true.
< Checks if the value of left operand is less than the value of right operand; if yes, then the condition becomes true. (A < B) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand; if yes, then the condition becomes true. (A >= B) is not true.
<= Checks if the value of left operand is less than or equal to the value of right operand; if yes, then the condition becomes true. (A <= B) is true.

逻辑运算符

下表显示了Swift 4语言支持的所有逻辑运算符。假设变量A保持1，变量B保持0，则-

Operator Description Example
&& Called Logical AND operator. If both the operands are non-zero, then the condition becomes true. (A && B) is false.
|| Called Logical OR Operator. If any of the two operands is non-zero, then the condition becomes true. (A || B) is true.
! Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true, then the Logical NOT operator will make it false. !(A && B) is true.

按位运算符

按位运算符对位进行运算并逐位执行操作。 ＆，|和^的真值表如下-

p q p&q p|q p^q
0 0 0 0 0
0 1 0 1 1
1 1 1 1 0
1 0 0 1 1 
Assume A = 60; and B = 13;

In binary format, they will be as follows:

A = 0011 1100

B = 0000 1101

-----------------

A & B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A = 1100 0011

下表列出了Swift 4语言支持的按位运算符。假设变量A保持60，变量B保持13，则7−

Operator Description Example
& Binary AND Operator copies a bit to the result, if it exists in both operands. (A & B) will give 12, which is 0000 1100
| Binary OR Operator copies a bit, if it exists in either operand. (A | B) will give 61, which is 0011 1101
^ Binary XOR Operator copies the bit, if it is set in one operand but not both. (A ^ B) will give 49, which is 0011 0001
~ Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. (~A ) will give -61, which is 1100 0011 in 2's complement form.
<< Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. (A << 2 will give 240, which is 1111 0000
>> Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. A >> 2 will give 15, which is 0000 1111

赋值运算符

SSwift 4支持以下赋值运算符-

Operator Description Example
= Simple assignment operator, Assigns values from right side operands to left side operand C = A + B will assign value of A + B into C
+= Add AND assignment operator, It adds right operand to the left operand and assigns the result to left operand C += A is equivalent to C = C + A
-= Subtract AND assignment operator, It subtracts right operand from the left operand and assigns the result to left operand C -= A is equivalent to C = C - A
*= Multiply AND assignment operator, It multiplies right operand with the left operand and assigns the result to left operand C *= A is equivalent to C = C * A
/= Divide AND assignment operator, It divides left operand with the right operand and assigns the result to left operand C /= A is equivalent to C = C / A
%= Modulus AND assignment operator, It takes modulus using two operands and assigns the result to left operand C %= A is equivalent to C = C % A
<<= Left shift AND assignment operator C <<= 2 is same as C = C << 2
>>= Right shift AND assignment operator C >>= 2 is same as C = C >> 2
&= Bitwise AND assignment operator C &= 2 is same as C = C & 2
^= bitwise exclusive OR and assignment operator C ^= 2 is same as C = C ^ 2
|= bitwise inclusive OR and assignment operator C |= 2 is same as C = C | 2

范围运算符

Swift 4包含两个range运算符，它们是表示一系列值的快捷方式。下表说明了这两个运算符。

Operator Description Example
Closed Range (a...b) defines a range that runs from a to b, and includes the values a and b. 1...5 gives 1, 2, 3, 4 and 5
Half-Open Range (a..< b) defines a range that runs from a to b, but does not include b. 1..< 5 gives 1, 2, 3, and 4
One- sided Range

a… , defines a range that runs from a to end of elements

…a , defines a range starting from start to a

1… gives 1 , 2,3… end of elements

…2 gives beginning… to 1,2

杂项运算符

Swift 4还支持其他一些重要的运算符，包括range和? ：如下表所述。

Operator Description Example
Unary Minus The sign of a numeric value can be toggled using a prefixed - -3 or -4
Unary Plus Returns the value it operates on, without any change. +6 gives 6
Ternary Conditional Condition ? X : Y If Condition is true ? Then value X : Otherwise value Y

运算符优先

运算符优先级确定表达式中术语的分组。这会影响表达式的求值方式。某些运算符具有更高的优先级；例如，乘法运算符的优先级高于加法运算符。

例如，x = 7 + 3 * 2;在这里，x被赋值为13，而不是20，因为运算符*的优先级比+高，因此它首先与3 * 2相乘，然后加到7。

在此，优先级最高的运算符出现在表格的顶部，优先级最低的运算符出现在表格的底部。在表达式中，优先级较高的运算符将首先被评估。

Operator Description Example
Primary Expression Operators () [] . expr++ expr-- left-to-right
Unary Operators

* & + - ! ~ ++expr --expr

* / %

+ -

>> <<

< > <= >=

== !=

 right-to-left
Binary Operators

&

^

|

&&

||

 left-to-right
Ternary Operator ?: right-to-left
Assignment Operators = += -= *= /= %= >>= <<= &=^= |= right-to-left
Comma , left-to-right