Lua - if...else statement

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An if statement can be followed by an optional else statement, which executes when the Boolean expression is false.

Syntax

The syntax of an if...else statement in Lua programming language is −

if(boolean_expression)
then
   --[ statement(s) will execute if the boolean expression is true --]
else
   --[ statement(s) will execute if the boolean expression is false --]
end

If the Boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed.

Lua programming language assumes any combination of Boolean true and non-nil values as true, and if it is either Boolean false or nil, then it is assumed as false value. It is to be noted that in Lua, zero will be considered as true.

Flow Diagram

Example

--[ local variable definition --]
a = 100;

--[ check the boolean condition --]

if( a < 20 )
then
   --[ if condition is true then print the following --]
   print("a is less than 20" )
else
   --[ if condition is false then print the following --]
   print("a is not less than 20" )
end

print("value of a is :", a)

When you build and run the above code, it produces the following result.

a is not less than 20
value of a is :	100

The if...else if...else Statement

An if statement can be followed by an optional else if...else statement, which is very useful to test various conditions using single if...else if statement.

While using if , else if , else statements, there are a few points to keep in mind −

• An if can have zero or one else's and it must come after any else if's.

• An if can have zero to many else if's and they must come before the else.

• Once an else if succeeds, none of the remaining else if's or else's will be tested.

Syntax

The syntax of an if...else if...else statement in Lua programming language is −

if(boolean_expression 1)
then
   --[ Executes when the boolean expression 1 is true --]

elseif( boolean_expression 2)
   --[ Executes when the boolean expression 2 is true --]

elseif( boolean_expression 3)
   --[ Executes when the boolean expression 3 is true --]
else 
   --[ executes when the none of the above condition is true --]
end

Example

--[ local variable definition --]
a = 100

--[ check the boolean condition --]

if( a == 10 )
then
   --[ if condition is true then print the following --]
   print("Value of a is 10" )
elseif( a == 20 )
then   
   --[ if else if condition is true --]
   print("Value of a is 20" )
elseif( a == 30 )
then
   --[ if else if condition is true  --]
   print("Value of a is 30" )
else
   --[ if none of the conditions is true --]
   print("None of the values is matching" )
end
print("Exact value of a is: ", a )

When you build and run the above code, it produces the following result.

None of the values is matching
Exact value of a is:	100