无涯教程-Lua - 运算符

运算符是一个符号，告诉解释器执行特定的数学或逻辑操作。 Lua语言具有丰富的内置运算符，并提供以下类型的运算符-

• 算术运算符
• 关系运算符
• 逻辑运算符
• 其它运算符

本教程将逐一说明算术，关系，逻辑和其他各种运算符。

算术运算符

下表显示了Lua语言支持的所有算术运算符。假设变量 A=10，变量 B=20，然后-

Operator	Remark	Example
+	加	A + B=30
-	减	A-B=-10
*	乘	A * B=200
/	除	B/A=2
％	模运算符和整数除后的余数	B％A=0
^	指数运算符取指数	A ^ 2=100
-	一元运算符,充当否定符	-A=-10

尝试以下示例以了解Lua编程语言中所有运算符的优先级-

a=20
b=10
c=15
d=5

e=(a + b) * c/d;-- ( 30 * 15 )/5
print("Value of (a + b) * c/d is   :",e )

e=((a + b) * c)/d; -- (30 * 15 )/5
print("Value of ((a + b) * c)/d is :",e )

e=(a + b) * (c/d);-- (30) * (15/5)
print("Value of (a + b) * (c/d) is :",e )

e=a + (b * c)/d;  -- 20 + (150/5)
print("Value of a + (b * c)/d is   :",e )

当您构建并执行上述程序时，它将产生以下输出-

Value of (a + b) * c/d is   :	90
Value of ((a + b) * c)/d is :	90
Value of (a + b) * (c/d) is :	90
Value of a + (b * c)/d is   :	50

关系运算符

下表显示了Lua语言支持的所有关系运算符。假设变量 A =10，变量 B=20，然后-

Operator	Remark	Example
==	相等	(A == B) is not true.
~=	如果值不相等,则条件为真。	(A ~= B) is true.
>	大于	(A > B) is not true.
<	小于	(A < B) is true.
>=	大于或等于	(A >= B) is not true.
<=	小于或等于	(A <= B) is true.

尝试以下示例以了解Lua编程语言中可用的所有关系运算符-

a=21
b=10

if( a == b )
then
   print("Line 1 - a is equal to b" )
else
   print("Line 1 - a is not equal to b" )
end

if( a ~= b )
then
   print("Line 2 - a is not equal to b" )
else
   print("Line 2 - a is equal to b" )
end

if ( a < b )
then
   print("Line 3 - a is less than b" )
else
   print("Line 3 - a is not less than b" )
end

if ( a > b ) 
then
   print("Line 4 - a is greater than b" )
else
   print("Line 5 - a is not greater than b" )
end

-- Lets change value of a and b
a=5
b=20

if ( a <= b ) 
then
   print("Line 5 - a is either less than or equal to  b" )
end

if ( b >= a ) 
then
   print("Line 6 - b is either greater than  or equal to b" )
end

当您构建并执行上述程序时，它将产生以下输出-

Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not less than b
Line 4 - a is greater than b
Line 5 - a is either less than or equal to  b
Line 6 - b is either greater than  or equal to b

逻辑运算符

下表显示了Lua语言支持的所有逻辑运算符。假设变量 A=true，变量 B=false，则-

Operator	Remark	Example
and	称为逻辑AND运算符。如果两个操作数都不为零,则条件为true。	(A和B)为假。
or	称为逻辑或运算符。如果两个操作数中的任何一个都不为零,则条件为true。	(A或B)为真。
not	称为逻辑非运算符。用于反转其操作数的逻辑状态。如果条件为真,则逻辑非运算符将为假。	!(A和B)为真。

请尝试以下示例，以了解Lua编程语言中可用的所有逻辑运算符-

a=5
b=20

if ( a and b )
then
   print("Line 1 - Condition is true" )
end

if ( a or b )
then
   print("Line 2 - Condition is true" )
end

--lets change the value ofa and b
a=0
b=10

if ( a and b )
then
   print("Line 3 - Condition is true" )
else
   print("Line 3 - Condition is not true" )
end

if ( not( a and b) )
then
   print("Line 4 - Condition is true" )
else
   print("Line 3 - Condition is not true" )
end

当您构建并执行上述程序时，它将产生以下输出-

Line 1 - Condition is true
Line 2 - Condition is true
Line 3 - Condition is true
Line 3 - Condition is not true

其它运算符

Lua语言支持的其他运算符包括 concatenation 和 length 。

Operator	Remark	Example
..	连接两个字符串。	a..b,其中a为" Hello",b为" World",将返回" Hello World"。
#	返回字符串或表格长度的一元运算符。	#"hello"将返回5

尝试以下示例以了解Lua编程语言中可用的其他运算符-

a = "Hello "
b = "World"

print("Concatenation of string a with b is ", a..b )

print("Length of b is ",#b )

print("Length of b is ",#"Test" )

当您构建并执行上述程序时，它将产生以下结果-

Concatenation of string a with b is 	Hello World
Length of b is 	5
Length of b is 	4

运算符优先级

在这里，优先级最高的运算符出现在表格的顶部，而优先级最低的运算符出现在表格的底部。

Category	Operator	Associativity
Unary	not # -	Right to left
Concatenation	..	Right to left
Multiplicative	*/%	Left to right
Additive	+ -	Left to right
Relational	< > <= >= == ~=	Left to right
Equality	== ~=	Left to right
Logical AND	and	Left to right
Logical OR	or	Left to right

尝试以下示例以了解Lua编程语言中所有运算符的优先级-

a=20
b=10
c=15
d=5

e=(a + b) * c/d;-- ( 30 * 15 )/5
print("Value of (a + b) * c/d is   :",e )

e=((a + b) * c)/d; -- (30 * 15 )/5
print("Value of ((a + b) * c)/d is :",e )

e=(a + b) * (c/d);-- (30) * (15/5)
print("Value of (a + b) * (c/d) is :",e )

e=a + (b * c)/d;  -- 20 + (150/5)
print("Value of a + (b * c)/d is   :",e )

当您构建并执行上述程序时，它将产生以下输出-

Value of (a + b) * c/d is   :	90
Value of ((a + b) * c)/d is :	90
Value of (a + b) * (c/d) is :	90
Value of a + (b * c)/d is   :	50

参考链接

https://www.learnfk.com/lua/lua-operators.html