Lua Conditionals

Conditionals are used to evaluate statements as true or false. They can be used to direct the flow of a program by specifying code blocks to run depending on the outcome of the expression.

The statement or condition can contain logic operators and variables.

If Statements

if <condition> then
  <code>
end

if..then statements run a block of code only when the condition is met. If the condition is false, the code block inside the if statement does not run. All conditional statements need to have an end keyword to close off the statement.

The following example demonstrates an if statement with a true condition:

a = 13
b = 16

if a < b then
  a = a + 5
end

print(a)
-- This prints 18 because a is less than b, so the code within the if statement was run which updates the value of a.

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The following code block demonstrates when the condition is now false:

a = 8
b = 10

if a==b then
  print(b + a)
end
-- Nothing is printed because a is not equal to b so the code statement was not executed.

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Else Statements

if <condition> then
  <code>
else
  <code>
end

In the event that the first condition is false, when there’s a subsequent else statement, the else statement will execute instead. Think of the else as an “if all else fails” plan. The else statement must go at the end and does not have a condition.

isNightTime = false

if isNightTime then
  print("Good night!")
else
  print("Good morning!")
end
-- This statement prints "Good morning!" because the if condition evaluated to false.

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ElseIf Statements

if <condition> then
  <code>
elseif <condition> then
  <code>
else
  <code>
end

elseif statements are similar to else statements but they can be used to create multiple actions instead of an either/or format. You can have multiple elseif statements, each with its own condition, but the final statement has to be an else statement.

player1 = 9

player2 = 12

if player1 >= 20 and player2 >= 20 then
  print( "Everyone wins!")
elseif player1 > player2 then
  print( "Player 1 wins with " .. player1 .. " points!")
elseif player1 < player2 then
  print( "Player 2 wins with " .. player2 .. " points!")
else
  print ("It’s a tie.")
end
-- This prints "Player 2 wins with 12 points" because it’s the first statement that evaluates to true.

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