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In this chapter we will talk about scripting in Lua, the tools required, In this chapter we will talk about scripting in Lua, the tools required,
and go over some techniques which you will probably find useful. and go over some techniques which you will probably find useful.
* Programming
* Tools * Tools
* Recommended Editors
* Integrated Programming Environments * Integrated Programming Environments
* Coding in Lua
* Selection
* Programming
* Local and Global * Local and Global
* Including other Lua Scripts * Including other Lua Scripts
## Programming
Teaching you how to program is beyond the scope of this book.
### Codecademy
[Codecademy](http://www.codecademy.com/) is one of the best resources for learning to 'code',
it provides an interactive tutorial experience.
### Scratch
[Scratch](https://scratch.mit.edu) is a good resource when starting from absolute basics,
learning the problem solving techniques required to program.\\
Programming is all about breaking down problems into steps a computer can manage.\\
Scratch is **designed to teach children** how to program, it isn't a serious programming language.
## Tools ## Tools
A text editor with code highlighting is sufficient for writing scripts in Lua. A text editor with code highlighting is sufficient for writing scripts in Lua.
@ -77,6 +66,141 @@ One such IDE is Eclipse with the Koneki Lua plugin:
* Start Minetest. * Start Minetest.
* Enter the game to startup Lua. * Enter the game to startup Lua.
## Coding in Lua
<div class="notice">
This section is a Work in Progress. May be unclear.
</div>
Programs are a series of commands that run one after another.
We call these commands "statements."
Program flow is important, it allows you to direct or skip over
statements. There are three main types of flow:
* Sequence: Just run one statement after another, no skipping.
* Selected: Skip over statements depending on conditions.
* Iteration: Repeating, looping. Keep running the same
statements until a condition is met.
So, what do statements in Lua look like?
{% highlight lua %}
local a = 2 -- Set 'a' to 2
local b = 2 -- Set 'b' to 2
local result = a + b -- Set 'result' to a + b, which is 4
a = a + 10
print("Sum is "..result)
{% endhighlight %}
Woah, what happened there? a, b and result are **variables**. They're like what
you get in mathematics, A = w * h. The equals signs are **assignments**, so
"result" is set to a + b. Variable names can be longer than one character
unlike in maths, as seen with the "result" variable. Lua is **case sensitive**.
A is a different variable to a.
The word "local" before they are first used means that they have local scope,
I'll discuss that shortly.
### Variable Types
| Type | Description | Example |
|----------|----------------------------------------------------|-------------------------------------------|
| Integer | Whole number | local A = 4 |
| Float | Decimal | local B = 3.2, local C = 5 / 2 |
| String | A piece of text | local D = "one two three" |
| Boolean | True or False | local is_true = false, local E = (1 == 1) |
| Table | Lists | Explained below |
| Function | Can run. May require inputs and may return a value | local result = func(1, 2, 3) |
Not an exhaustive list. Doesn't contain every possible type.
### Arithmetic Operators
| Symbol | Purpose | Example |
|--------|----------------|---------------------------|
| A + B | Addition | 2 + 2 = 4 |
| A - B | Subtraction | 2 - 10 = -8 |
| A * B | Multiplication | 2 * 2 = 4 |
| A / B | Division | 100 / 50 = 2 |
| A ^ B | Powers | 2 ^ 2 = 2<sup>2</sup> = 4 |
| A .. B | Join strings | "foo" .. "bar" = "foobar" |
A string in programming terms is a piece of text.
Not an exhaustive list. Doesn't contain every possible operator.
### Selection
The most basic selection is the if statement. It looks like this:
{% highlight lua %}
local random_number = math.random(1, 100) -- Between 1 and 100.
if random_number > 50 then
print("Woohoo!")
else
print("No!")
end
{% endhighlight %}
That example generates a random number between 1 and 100. It then prints
"Woohoo!" if that number is bigger than 50, overwise it prints "No!".
What else can you get apart from '>'?
### Logical Operators
| Symbol | Purpose | Example |
|---------|--------------------------------------|-------------------------------------------------------------|
| A == B | Equals | 1 == 1 (true), 1 == 2 (false) |
| A ~= B | Doesn't equal | 1 ~= 1 (false), 1 ~= 2 (true) |
| A > B | Greater than | 5 > 2 (true), 1 > 2 (false), 1 > 1 (false) |
| A < B | Less than | 1 < 3 (true), 3 < 1 (false), 1 < 1 (false) |
| A >= B | Greater than or equals | 5 >= 5 (true), 5 >= 3 (true), 5 >= 6 (false) |
| A <= B | Less than or equals | 3 <= 6 (true), 3 <= 3 (true) |
| A and B | And (both must be correct) | (2 > 1) and (1 == 1) (true), (2 > 3) and (1 == 1) (false) |
| A or B | either or. One or both must be true. | (2 > 1) or (1 == 2) (true), (2 > 4) or (1 == 3) (false) |
| not A | not true | not (1 == 2) (true), not (1 == 1) (false) |
That doesn't contain every possible operator, and you can combine operators like this:
{% highlight lua %}
if not A and B then
print("Yay!")
end
{% endhighlight %}
Which prints "Yay!" if A is false and B is true.
Logical and arithmetic operators work exactly the same, they both accept inputs
and return a value which can be stored.
{% highlight lua %}
local A = 5
local is_equal = (A == 5)
if is_equal then
print("Is equal!")
end
{% endhighlight %}
## Programming
Programming is the action of talking a problem, such as sorting a list
of items, and then turning it into steps that a computer can understand.
Teaching you the logical process of programming is beyond the scope of this book,
however the following websites are quite useful in developing this:
### Codecademy
[Codecademy](http://www.codecademy.com/) is one of the best resources for learning to 'code',
it provides an interactive tutorial experience.
### Scratch
[Scratch](https://scratch.mit.edu) is a good resource when starting from absolute basics,
learning the problem solving techniques required to program.\\
Scratch is **designed to teach children** how to program, it isn't a serious programming language.
## Local and Global ## Local and Global
Whether a variable is local or global determines where it can be written to or read to. Whether a variable is local or global determines where it can be written to or read to.