Conditionals

Conditionals let you choose which code runs.

local fps = 120

if fps >= 60 then
    lh.drawln("Your computer is very strong!")
end

The code between then and end runs only when the condition is truthy.

else and elseif

Use else for an alternative, and elseif to check more conditions:

local fps = 120

if fps < 60 then
    lh.drawln("How long do you bake your pc for?")
elseif fps < 200 then
    lh.drawln("Your computer is very strong!")
else
    lh.drawln("NASA wants your computer.")
end

Lua checks from top to bottom and runs only the first matching branch. Here, the second branch covers FPS from 60 up to, but not including, 200. else covers 200 and above.

elseif is one word. You only need one end for the whole chain.

What if the condition is not a boolean?

Lua treats only false and nil as false in a condition. These are called falsy values. All other values are truthy, including 0, "", and {}. The value itself is not converted or changed.

local health = 0

if health then
    lh.drawln("A health value exists.") -- This runs even when health is 0.
end

if health > 0 then
    lh.drawln("You are alive.") -- This does not run.
end

To check whether a value exists while allowing false, write value ~= nil.

Combining conditions

Use and, or, and not to combine checks:

local fps = 45
local showWarnings = true

if showWarnings and fps < 60 then
    lh.drawln("Try lowering your graphics settings.")
end

Write ranges as fps >= 60 and fps < 200. Chaining comparisons as 60 <= fps < 200 does not work in Lua.

Choosing a value

Lua does not have a ternary operator, but this pattern is common:

local fps = 120
local message = fps >= 60 and "Smooth!" or "Low FPS"
lh.drawln(message) -- Output: Smooth!

When the condition is true, and returns "Smooth!". Since that is truthy, or keeps it. Otherwise, or returns "Low FPS".

Caution

This pattern fails if the value after and is false or nil, because or will choose the fallback. Use an ordinary if instead:

local hidden = true
local message

if hidden then
    message = nil
else
    message = "Visible"
end