Aliases

An alias declaration binds an identifier to an existing type. All the properties of the existing type are bound to the alias too.

There are two type of aliasing:

• aliasing
• extending

Aliasing

typ[ali] I5: arr[int, 5];

So now the in the code, instead of writing arr[int, 5] we could use I5:

~var[pub] fiveIntigers: I5 = { 0, 1, 2, 3, 4, 5 }

Another example is creating a rgb type that can have numbers only form 0 to 255:

typ[ali] rgb: int[8][.range(255)] ;                        // we create a type that holds only number from 0 to 255
typ[ali] rgbSet: set[rgb, rgb, rgb];                       // then we create a type holding the `rgb` type

Alias declaration are created because they can simplify using them multiple times, their identifier (their name) may be expressive in other contexts, and–most importantly–so that you can define (attach) methods to it (you can't attach methods to built-in types, nor to anonymous types or types defined in other packages).

Attaching methods is of outmost importance, because even though instead of attaching methods you could just as easily create and use functions that accept the "original" type as parameter, only types with methods can implement standards std[] that list/enforce those methods, and you can't attach methods to certain types unless you create a new type derived from them.

Extending

Extensions add new functionality to an existing constructs. This includes the ability to extend types for which you do not have access to the original source code (known as retroactive modeling).

typ[ext] type: type;

For example, adding a print function to the default integer type int:

typ[ext] int: int;

pro (int)print(): non = {
    .echo(self)
}

pro main: int = {
    5.print()                   // method print on int
}

Or turning a string str into a vector of characters:

typ[ext] str: str;

fun (str)to_array(): vec[chr] = {
    loop(x in self){
        yeild x; 
    }
}


pro main(): int = {
    var characters: vec[chr] = "a random str".to_array();

    .echo(characters)           // will print: {"a"," ","r","a","n","d","o","m"," ","s","t","r"}
}