Basics

Some Lua and Kipt basics to get started with the scripting:

Lua basics

In Lua, only 8 types are used. In the context of Kipt, you only need 5 of them if you want to keep it simple:

• nil: nothing / no value.
• number
• string
• table
• boolean

Except for table, the other types are very common.

You can notice that there are no array, but table is flexible enough to be used as hashmap and array.

-- nil
local a = nil

-- Number
local b = 1234

-- String
local c = "kipt"

-- Boolean
local d = false

-- Table
local e = { a = 2, b = "abc" }

-- Table (array-like)
local f = { 1, 2, 3, 4 }

The use of local is optional, but it's a good practice as any variable without local is considered as global. So if you use some functions for more advanced Lua programming, keep the use of local.

In case of array, under the hood it's a table, but index starting to 1 (nobody is perfect...).

To access member of an table, you have two notations as showed below. If the key does not exist, it returns nil.

local t = { a = 2, b = "abc" }
print(t.a)
print(t["b"])

if t.h then
    -- h is not nil and has a value, do stuff with it.
end

To test nil, the best practice is to compare with nil, this is because nil and false are evaluated the same way:

local a = false
local b = nil

if not a and not b then
    print("will be printed")
end

if a == nil and b == nil then
    print("will not be printed")
end

This are all the basics you need to get started.