Lua operator
An operator is a special symbol that tells the interpreter to perform specific mathematical or logical operations. Lua provides the following types of operators:
Arithmetic operator
Relational operator
Logical operator
Other operators
Arithmetic operator
The following table lists the common arithmetic operators in the Lua language, setting A to 10 and B to 20:
Operator |
Description |
Example |
|---|---|---|
|
Addition |
A + B output result 30 |
|
Subtraction |
A-B output result-10 |
|
Multiplication |
A * B output result 200 |
|
Division |
B / A output result 2 |
|
Take the remainder |
B An output result 0 |
|
Multiplying power |
A^2 output result 100 |
|
Minus sign |
-A output result-10 |
|
Integer division operator (> = lua5.3) |
5Compact 2 output result 2 |
Example
We can understand the application of arithmetic operators more thoroughly through the following examples:
Example
a = 21
b = 10
c = a + b
print("The value of Line 1- c is ", c )
c = a - b
print("The value of Line 2- c is ", c )
c = a * b
print("The value of Line 3- c is ", c )
c = a / b
print("The value of Line 4- c is ", c )
c = a % b
print("The value of Line 5- c is ", c )
c = a^2
print("The value of Line 6- c is ", c )
c = -a
print("The value of Line 7-c is ", c )
The execution results of the above procedures are as follows:
The value of Line 1- c is 31
The value of Line 2- c is 11
The value of Line 3- c is 210
The value of Line 4- c is 2.1
The value of Line 5- c is 1
The value of Line 6- c is 441
The value of Line 7- c is -21
In lua, / is used as a division operation, the result contains the decimal part, // is used as an integral division operation, and the result does notinclude the decimal part:
Example
a = 5
b = 2
print("The value of division operation - a/b is ", a / b )
print("The value of integer division - a/b is ", a // b )
The execution results of the above procedures are as follows:
Division operation - the value of a/b is 2.5
The value of integer division - a/b is 2
Relational operator
The following table lists the common relational operators in the Lua language, setting the value of A to 10 and the value of B to 20:
Operator |
Description |
Example |
|---|---|---|
== |
Equals, checks whether two values are equal, returns true, otherwise returnsfalse |
(A == B) is false. |
~= |
Not equal. Check whether two values are equal. Return true if they are not equal, otherwise return false. |
(A ~= B) is true. |
> |
Greater than, if the value on the left is greater than the value on the right, return true, otherwise return false |
(A > B) is false. |
< |
Less than, if the value on the left is greater than the value on the right, return false, otherwise return true |
(A < B) is true. |
>= |
Greater than or equal to, if the value on the left is greater than or equal to the value on the right, return true, otherwise return false |
(A >= B) returns false. |
<= |
Less than or equal to, if the value on the left is less than or equal to thevalue on the right, return true, otherwise return false |
(A <= B) returns true. |
Example
We can understand the application of relational operators more thoroughly through the following examples:
Example
a = 21
b = 10
if( a == b )
then
print("Line 1 - a = b" )
else
print("Line 1 - a ≠ b" )
end
if( a ~= b )
then
print("Line 2 - a ≠ b" )
else
print("Line 2 - a = b" )
end
if ( a < b )
then
print("Line 3 - a < b" )
else
print("Line 3 - a ≥ b" )
end
if ( a > b )
then
print("Line 4 - a > b" )
else
print("Line 5 - a ≤ b" )
end
-- Modify the values of a and b
a = 5
b = 20
if ( a <= b )
then
print("Line 5 - a ≤ b" )
end
if ( b >= a )
then
print("Line 6 - b ≥ a" )
end
The execution results of the above procedures are as follows:
Line 1 - a ≠ b
Line 2 - a ≠ b
Line 3 - a ≥ b
Line 4 - a > b
Line 5 - a ≤ b
Line 6 - b ≥ a
Logical operator
The following table lists the common logical operators in the Lua language, setting the value of A to true , the value of B is false :
Operator |
Description |
Example |
|---|---|---|
and |
Logic and operators. If A is false, return A, otherwise return B. |
(A and B) is false. |
or |
Logic or operator. If A is true, return A, otherwise return B. |
(A or B) is true. |
not |
Logical non-operator. Contrary to the logic operation result, if the condition is true, the logic is not false. |
not (A and B) is true. |
Example
We can understand the application of logical operators more thoroughly through the following examples:
Example
a = true
b = true
if ( a and b )
then
print("a and b - Condition is true" )
end
if ( a or b )
then
print("a or b - Condition is true" )
end
print("---------Divider---------" )
-- Modify the values of a and b
a = false
b = true
if ( a and b )
then
print("a and b - Condition is true" )
else
print("a and b - Condition is false" )
end
if ( not( a and b) )
then
print("not( a and b) - Condition is true" )
else
print("not( a and b) - Condition is false" )
end
The execution results of the above procedures are as follows:
a and b - Condition is true
a or b - Condition is true
---------Divider---------
a and b - Condition is false
not( a and b) - Condition is true
Other operators
The following table lists the concatenation operators in the Lua language and operators that calculate the length of a table or string:
Operator |
Description |
Example |
|---|---|---|
Concatenate two strings |
a..b, where an is “Hello”, b is “World”, and the output is “Hello World”. |
|
# |
Unary operator that returns the length of a string or table. |
#”Hello” returns 5 |
Example
We can better understand the application of concatenation operators and operators that calculate the length of tables or strings through the following examples:
Example
a = "Hello "
b = "World"
print("Connection strings a and b ", a..b )
print("B String length ",#b )
print("String Test Length ",#"Test" )
print("Newbie tutorial website length ",#"www.runoob.com" )
The execution results of the above procedures are as follows:
Connection strings a and b Hello World
B String length 5
String Test Length 4
Newbie tutorial website length 14
Operator precedence
The order from high to low:
^
not - (unary)
* / %
+ -
..
< > <= >= ~= ==
and
or
Except ^ and .. all binary operators outside are left concatenated.
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)
Example
We can get a more thorough understanding of the precedence of Lua language operators through the following examples:
Example
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 execution results of the above procedures are as follows:
(a + b) * c / d operation value is : 90.0
((a + b) * c) / d operation value is : 90.0
(a + b) * (c / d) operation value is : 90.0
a + (b * c) / d operation value is : 50.0