View source for S2 Guide: Language Tutorial

S2 is a programming language designed to be a style system.  It has properties in common with Perl, Python, and Java.  As a programming language, it is:

* Object oriented: You can define classes that bundle up functions and variables into an object.
* Statically typed: Variables must be assigned a type, and that type does not change.

= Variables =

Variables are like containers that hold values.  You can put values into them, use their values in your programming, or change their value to something else.

== Declaring a variable ==

In S2, variables must be declared ahead of time in order to be used.  The basic format goes:

 var TYPE variablename;

* <tt>var</tt> indicates you're creating a new variable
* <tt>TYPE</tt> describes what type of variable you're making. The type can be one of the basic types, described below, or a previously defined class (to be explained later).  This type doesn't change.
* <tt>variablename</tt> is the name you give the variable in your code. This name must start with a letter and can contain letters, digits, and the underscore character ("_"). 

You can assign a variable a value when declaring it, or wait until later--but make sure to assign a variable a value before you use it!  An example of declaring a variable while assigning it is:

 var TYPE variablename = VALUE;

Or, in real code:

<syntaxhighlight lang="s2">var string greetings = "hello";</syntaxhighlight>

Note: you can assign the value of a variable to another variable, as well, if they are the same type.  Here's an example that gives <tt>variable1</tt> the value of <tt>variable2</tt>:

 var TYPE variable1 = $variable2;

Or, in real code:

<syntaxhighlight lang="s2">var string goodbye = greetings;</syntaxhighlight>

== Basic Types ==

=== Strings ===

String variables, which are lists of characters, are declared as <tt>string</tt> in S2.  You can define strings in one of two ways.

The first way comes in between double quotes:

<syntaxhighlight lang="s2">
var string test = "Testing"; 
</syntaxhighlight>

The second way comes in between sets of three double quotes--this is very useful when writing HTML, which can have a lot of single double quotes in it.  Here's an example:

<syntaxhighlight lang="s2">
"""I am also a string, but I can have "quotes" inside me.""";
</syntaxhighlight>

The above example demonstrates another property of string values, in that if you don't assign them to a variable name, they'll print to output.

Some characters need to be escaped to show up properly in strings, with a backslash (\):

* If you need a newline, use: <tt>\n</tt>
* If you need a double quote inside single double quotes (or need to make three or more double quotes inside a triple double quotes), use: <tt>\"</tt>
* If you need to make a backslash, use: <tt>\\</tt>
* If you want to make a dollar sign (you'll learn why later in variables), use: <tt>\$</tt>

=== Integers ===

Integers (whole numbers) are another value like strings that the S2 language understands, and are declared with <tt>int</tt>. This is an example of a variable being assigned a literal integer value:

<syntaxhighlight lang="s2">
var int width = 500;
</syntaxhighlight>

=== Booleans ===

A boolean is a variable that is either <tt>true</tt> or <tt>false</tt>, and is declared with <tt>bool</tt>.  Here is an example that expresses having candy but no cake as boolean variables:

<syntaxhighlight lang="s2">
var bool has_candy = true;
var bool has_cake = false;
</syntaxhighlight>

== Arrays ==

An array is a list of items.  They must all be the same type!  Declaring an array variable is a little different from the usual variable declaration:

 var TYPE[] variablename;

The <tt>[]</tt> after the type lets the program know this variable is an array.

Here is an example with strings:

<syntaxhighlight lang="s2">
var string[] counting = ["one", "two", "three"]
</syntaxhighlight>

=== Associative arrays ===

Instead of an ordered list of items, an associative array gives each item in it a "key" that serves as an identifying label.  All keys must be strings, and all the times must be the same type.  Like regular arrays, declaring associative arrays is a little different:

 var TYPE{} variablename;

The <tt>{}</tt> after the type lets the program know this variable is an associative array.

Here's an example with strings:

<syntaxhighlight lang="s2">
var string{} fruits = ["apple" => "red", "lemon" => "yellow", "grape" => "purple"]
</syntaxhighlight>

== Accessing variables ==

Putting a <tt>$</tt> in front of the variable name lets you access it: <tt>$variablename</tt>.  Remember how in strings, the dollar sign needed to be escaped like <tt>\$</tt>?  That's because when you reference a variable in a string, it's replaced with the value of the variable!  For instance, this code:

<syntaxhighlight lang="s2">
var string greeting = "hi";
print "I greet you with: $greeting\n";
$greeting = "hello";
print "I greet you with: $greeting\n";
</syntaxhighlight>

Will print out:

 I greet you with hi
 I greet you with hello

For regular arrays, you'll need to refer to the position of the value you want in the array; the count starts at <tt>0</tt>.  Example:

<syntaxhighlight lang="s2">
var string[] counting = ["one", "two", "three"]
print "I have $counting[2] bananas and $counting[1] apples and $counting[0] orange.\n";
</syntaxhighlight>

Will print out:

 I have three bananas and two apples and one orange.

For associative arrays, you'll want to use the key of the value you want.  Example:

<syntaxhighlight lang="s2">
var string{} fruits = ["apple" => "red", "lemon" => "yellow", "grape" => "purple"]
print "I have $fruits{"grape"}-colored pants.\n";
</syntaxhighlight>

Will print out:

 I have purple-colored pants.

== Properties ==

Properties are special global variables that are available between layers.  EXPAND

= Statements =

= Operators =

= Functions =

== Classes ==

[[Category: S2 Guide]]