For those coming from the likes of C++ and C#, generics will be nothing new to you. It is typically represented as T. It is used in the same way as a standard type. As T doesn't actually have a type, it's known a polymorphic parameter.
There's a simple rule regarding generic types.
The types have to match—if we define T as being f64 and attempt to assign a String to it, the compiler will fail to build that code.
While T is also (probably) the most commonly used letter for a generic type, in reality you can have any letter, or even words.
For example, this is perfectly acceptable code:
enum Result<Y, N>
{
Ok(Y),
Err(N),
} Y and N do not need to be the same type either; therefore, Y could be a String and N a bool.
In practice, the following shows how the generic type works. Option is provided as part of the standard library:
enum Option<T>
{
Some_Type(T),
None
}
let varname: Option<f32> = Some_Type(3.1416f32); Generics also provide another useful...