Lua Operators

Operators are special symbols that tell the interpreter to perform specific mathematical or logical operations. Lua provides the following types of operators:

Arithmetic Operators
Relational Operators
Logical Operators
Other Operators

Arithmetic Operators

The following table lists the common arithmetic operators in the Lua language. Assume the value of A is 10 and the value of B is 20:

Operator	Description	Example
+	Addition	A + B outputs 30
-	Subtraction	A - B outputs -10
*	Multiplication	A * B outputs 200
/	Division	B / A outputs 2
%	Modulus	B % A outputs 0
^	Exponentiation	A^2 outputs 100
-	Negative sign	-A outputs -10
//	Floor division operator (>=lua5.3)	5//2Outputs 2

Examples

We can understand the application of arithmetic operators more thoroughly through the following examples:

Examples

a = 21
b = 10
c = a + b
print("Line 1 - The value of c is ", c )
c = a - b
print("Line 2 - The value of c is ", c )
c = a * b
print("Line 3 - The value of c is ", c )
c = a / b
print("Line 4 - The value of c is ", c )
c = a % b
print("Line 5 - The value of c is ", c )
c = a^2
print("Line 6 - The value of c is ", c )
c = -a
print("Line 7 - The value of c is ", c )

The output of the above program is:

Line 1 - c 的值为     31
Line 2 - c 的值为     11
Line 3 - c 的值为     210
Line 4 - c 的值为     2.1
Line 5 - c 的值为     1
Line 6 - c 的值为     441
Line 7 - c 的值为     -21

In Lua,// is used for division operations, and the calculation result includes the decimal part.//// is used for floor division operations, and the calculation result does not include the decimal part:

Examples

a = 5
b = 2

print("Division operation - The value of a/b is ", a / b )
print("Floor division operation - The value of a//b is ", a // b )

The output of the above program is:

除法运算 - a/b 的值为   2.5
整除运算 - a//b 的值为  2

Relational Operators

The following table lists the common relational operators in the Lua language. Assume the value of A is 10 and the value of B is 20:

Operator	Description	Example
==	Equal to, checks whether two values are equal. If they are equal, returns true; otherwise, returns false.	(A == B) is false.
~=	Not equal to, checks whether two values are equal. If they are not equal, returns true; otherwise, returns false.	(A ~= B) is true.
>	Greater than, if the left value is greater than the right value, returns true; otherwise, returns false.	(A > B) is false.
<	Less than, if the left value is greater than the right value, returns false; otherwise, returns true.	(A < B) is true.
>=	Greater than or equal to, if the left value is greater than or equal to the right value, returns true; otherwise, returns false.	(A >= B) returns false.
<=	Less than or equal to, if the left value is less than or equal to the right value, returns true; otherwise, returns false.	(A <= B) returns true.

Examples

We can understand the application of relational operators more thoroughly through the following examples:

Examples

a = 21
b = 10

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

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

if ( a < b )
then
print("Line 3 - a is less than b" )
else
print("Line 3 - a is greater than or equal to b" )
end

if ( a > b )
then
print("Line 4 - a is greater than b" )
else
print("Line 5 - a is less than or equal to b" )
end

-- Modify the values of a and b
a = 5
b = 20
if ( a <= b )
then
print("Line 5 - a is less than or equal to b" )
end

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

The output of the above program is:

Line 1 - a 不等于 b
Line 2 - a 不等于 b
Line 3 - a 大于等于 b
Line 4 - a 大于 b
Line 5 - a 小于等于  b
Line 6 - b 大于等于 a

Logical Operators

The following table lists the common logical operators in the Lua language. Assume the value of A is true and the value of B is false:

Operator	Description	Example
and	Logical AND operator. If A is false, returns A; otherwise, returns B.	(A and B) is false.
or	Logical OR operator. If A is true, returns A; otherwise, returns B.	(A or B) is true.
not	Logical NOT operator. It is opposite to the logical operation result. If the condition is true, the logical NOT is false.	not(A and B) is true.

Examples

We can understand the application of logical operators more thoroughly through the following examples:

Examples

a = true
b = true

if ( a and b )
then
print("a and b - The condition is true" )
end

if ( a or b )
then
print("a or b - The condition is true" )
end

print("---------Separator---------" )

-- Modify the values of a and b
a = false
b = true

if ( a and b )
then
print("a and b - The condition is true" )
else
print("a and b - The condition is false" )
end

if ( not( a and b) )
then
print("not( a and b) - The condition is true" )
else
print("not( a and b) - The condition is false" )
end

The output of the above program is:

a and b - 条件为 true
a or b - 条件为 true
---------分割线---------
a and b - 条件为 false
not( a and b) - 条件为 true

Other Operators

The following table lists the concatenation operators and the operators for calculating the length of tables or strings in the Lua language:

Operator	Description	Example
..	Concatenates two strings	a..b, where a is "Hello " and b is "World", the output result is "Hello World".
#	Unary operator that returns the length of a string or table.	#"Hello" returns 5

Examples

We can understand the application of the concatenation operators and the operators for calculating the length of tables or strings more thoroughly through the following examples:

Examples

a = "Hello "
b = "World"

print("Concatenate strings a and b ", a..b )

print("The length of string b ",#b )

print("The length of the string Test ",#"Test" )

print("The length of the Example tutorial website URL ",#"www.example.com" )

The output of the above program is:

连接字符串 a 和 b     Hello World
b 字符串长度     5
字符串 Test 长度     4
Example网址长度     14

Operator Precedence

From highest to lowest:

^
not    - (unary)
*      /       %
+      -
..
<      >      <=     >=     ~=     ==
and
or

Except for^and..all other binary operators are left-associative.

a+i < b/2+1          <-->       (a+i) < ((b/2)+1)
5+x^2*8              <-->       5+((x^2)*8)
a < y and y <= z     <-->       (a < y) and (y <= z)
-x^2                 <-->       -(x^2)
x^y^z                <-->       x^(y^z)

Examples

We can understand the operator precedence of the Lua language more thoroughly through the following examples:

Examples

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

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

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

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

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

The output of the above program is:

(a + b) * c / d 运算值为  :    90.0
((a + b) * c) / d 运算值为 :    90.0
(a + b) * (c / d) 运算值为 :    90.0
a + (b * c) / d 运算值为   :    50.0

Other Extensions