Lua Syntax Cheat Sheet (Short Version)

-- Single line comment

--[[
    Block comment
    Everything inside this block is
    treated as a comment
--]]

numValue = 42  -- number (integer)
numFloatValue = 10.37 -- number (float)
stringValue = "Hello World!" -- string
boolValue = true -- boolean

-- String concatenation operator ..
"Hello" .. " " .. "World" -- "Hello world"

num = 1
num = num + 1 -- increment
num = num - 1 -- decrement 
num = 42 + 10 -- addition
num = 42 * 10 -- multiplication
num = 42 % 10 -- modulus
num = 42 - 10 -- subtraction
num = 42 / 10 -- division
num = 2 ^ 10  -- power

if num == 0 then
    print("num is equal 0")
end

if num > 1 then
    print("num is greater than 1")
elseif num < 1 then
    print("num is less than 1")
else
    print("num is equal to 1")
end

while num < 50 do
    print(num)
    num = num + 1
end

-- First parameter: start
-- Second paramenter stop
-- (Optional, default = 1) Third parameter: step
for i = 1, 100, 1 do
    print(num)
    num = num + 1
end

repeat
    print(num)
    num = num + 1
until num > 10

t = {} -- Creates empty table (table constructor)
t[1] = "a" -- Put character 'a' at index 1

t["lua"] = 20 -- `t` contains 20 at index "lua"
t[1] = nil -- Removes value stored at index 1

t.name = "Victoria"  -- t["name"] contains string "Victoria"

t2 = {2, 3, 4} -- Creates table with 2 stored at index 1,
               -- 3 stored at index 2, and 5 at index 3

-- Iterate through all values in a table.
-- i current index
-- n value at current index
for i, n in ipairs(t2) do
    print(i, n)
end

-- # table size
print(#t2) -- prints 3

function isNegative(n)
    return n < 0
end

isNegative(-42) -- returns true
isNegative(42)  -- returns false

-- Multiple arguments
function fullName(firstName, lastName)
    return string.format("%s %s", firstName, firstName)
end

-- Assign function to a variable.
negFn = isNegative
negFn(20) -- Returns false