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Enums in Rust Programing
Also referred to as enumerations, enums are very useful in certain cases. In Rust, we use enums, as they allow us to define a type that may be one of a few different variants.
Enumerations are declared with the keyword enum.
Example
#![allow(unused)] #[derive(Debug)] enum Animal { Dog, Cat, } fn main() { let mut b : Animal = Animal::Dog; b = Animal::Cat; println!("{:?}",b); }
Output
Cat
Zero-variant Enums
Enums in Rust can also have zero variants, hence the name Zero-variant enums. Since they do not have any valid values, they cannot be instantiated.
Zero-variant enums are equivalent to the never type in Rust.
Example
#![allow(unused)] #[derive(Debug)] enum ZeroVariantEnum {} fn main() { let x: ZeroVariantEnum = panic!(); println!("{:?}",x); }
Output
thread 'main' panicked at 'explicit panic', src/main.rs:7:30
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