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title Chapter 2 - Value Types, Declaration & Assignment
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Chapter 2 - Value Types, Declaration & Assignment

What will you learn in this chapter

In this chapter you will learn about:

The knowledge in this chapter is crucial to continue further. Data types are an extensive subject, but you don't need to know everything. This chapter's goal is to teach you how to handle value types in your script.

Note

This chapter won't cover every detail of every data type. It is recommended you visit the Data Types Section of the Wiki for more information. Alternatively, you can find references on the AS Official Documentation. Please note, however, that the Strata Wiki is a better reference, as some functionality may have been changed.

Value Types

Value types are a more "primitive" type, and are only implemented in the backend inside the engine itself. These types include: int, string, bool, float, double, etc.

Warning

It is assumed you already know about these data types from other languages (mainly C++). This subsection will only provide information relevant to AngelScript itself.

Declaration and Assignment

Value types can be easily assigned and can passed by value to functions. We'll get into that more later. To create a value type, you will usually perform a declaration, an assignment, or both at once:

int myInt; // Declaration
myInt = 20; // Assignment

string myString = "Hey!"; // Initialization

You can declare multiple variables of the same type at once:

int myInt1, myInt2, myInt3;

Once declared, variables cannot change their type without redeclaration. This, for example, is not allowed:

int myInt;
myInt = 3.2; // myInt is of type int, not float/double!

TASK 1:

  1. Create a program that will declare and assign variables of types string, int, bool, double, and then print them out to the console.
  2. Do the same using variable initialization.

Auto Keyword

Although not recommended, the auto keyword will make the compiler automatically determine the data type of the variable:

auto i = 1; // Will set type of i to integer
auto s = "My string"; // Will set type s to string
auto var = functionThatWillReturnAnObjectWithAVeryLongName();

// Handles (described in later chapters) can also be declared with auto
auto@ handle = @obj;

The auto keyword is not recommended in many cases. Using auto, you cannot immediately see the data type of a returned object, especially from functions such the one above. We don't know what that function will return. Additionally, there is always a chance the compiler may guess incorrectly. This issue is especially prominent in cases such as integers, where there are multiple ways 1 could be described (e.g. int8/int16, both can describe 1, as can bool).

Constants

Constant variables are variables that cannot change over the lifetime of the variable scope they are created in. You can define a constant variable using the const keyword:

const int size = 31;
const auto st = "string"; // const also works with the auto keyword

Constants can be useful as a sort of configuration of the script itself. Instead of reusing a statically-defined variable, you can define a global constant in its place. Changing one value will then change everything at once:

const int MAX_SIZE = 16;

string mystring = "lorem ipsum";
my_func1(mystring, MAX_SIZE); // A function that does something with mystring, but also needs to have additional information
my_func2(mystring, MAX_SIZE) // Another function that does something else with mystring, but it also needs the same additional information

Constants also function as a way to optimize your code. If you know that a variable won't change (or shouldn't change) after its initialization, you should always make it a constant.

bool function(string s, float i) {
    const float value = s.length() - i;
    return i > value;
}

TASK 2:

Write a program that initializes a constant variable with the auto keyword, and then tries to change it after. Observe the compilation error in the console.

Integer Size Reference Table

The table below shows the minimum and maximum values for each integer subtype. It is not necessary to memorize this chart as you can always refer back to this page when necessary.

Type Short description Minimum Value Maximum Value
int8 Signed, 8 bits -128 127
int16 Signed, 16 bits -32,768 32,767
int Signed, 32 bits -2,147,483,648 2,147,483,647
int64 Signed, 64 bits -9,223,372,036,854,775,808 9,223,372,036,854,775,807
uint8 Unsigned, 8 bits, also represents characters (char) 0 255
uint16 Unsigned, 16 bits 0 65,535
uint Unsigned, 32 bits 0 4,294,967,295
uint64 Unsigned, 64 bits 0 18,446,744,073,709,551,615

Tip

The official AngelScript documentation mentions that the scripting engine has been mostly optimized for 32 bit datatypes (int/uint). Using these is recommended for the most part (unless you are dealing with numbers that don't fit into int/uint).