Numbers

Lua uses integers and doubles as number values.

Technically, Lua only has Numbers. Integers are represented through a double, but for our purposes, it can be necessary to differentiate. Because of this, I will sometimes talk about integers and doubles as if they are separate types.

Integers

An integer is a number, negative or positive, that does not have a decimal point. We can perform normal arithmetic operations on them.

local counter = 0
local num = 100

counter = counter + 1
num = num * 2

local p = num ^ counter

local x = p % 10

x = x / 2

Unfortunately, Lua does not have a shorthand increment. No counter++ for us.

Bitwise Operations

When a number value has no decimal point, it's valid for bitwise operations.

local counter = 1

-- 3
counter = counter | 2
print(counter)

-- 3
counter = counter | 2
print(counter)

-- 1
counter = counter & ~2
print(counter)

and so on.

Note that ~ is used as NOT. It can also be used as XOR.

-- 0, 1, 1, 0
print(1 ~ 1)
print(1 ~ 0)
print(0 ~ 1)
print(0 ~ 0)

Similar to the differencee between a negative number and subtraction, use a space.

Doubles

You can think of a double as a decimal number.

local x = 1.7
x = x * 3
x = x + 2.34

If the decimal is 0, it'll be treated as an integer.

-- No error
local x = 1.0
x = x | 2

-- This gets an error
x = 1.5
x = x | 2

Conversions

If the result of an operation on an integer ends with a value that has a decimal, you'll have a double. That could be adding a double to an integer, or dividing by a number that doesn't divide perfectly.

local x = 5
x = x | 2
x = x + 1.2
-- x has a decimal, so this will throw an error.
x = x | 1

If you're unsure of the state of a number after doing some operations on it and you need an integer, math.floor or math.ceil will cut off the decimal. Prefer math.floor for calculations in your mods, since the original games would.

-- No error
local x = 1.5
x = math.floor(x) | 2