pub const fn singleton(head: T) -> Self {
        NonEmpty {
            head,
            tail: Vec::new(),
        }
    }
/// Create a new non-empty list with an initial element.
Create a new non-empty list with an initial element.
Create a new non - empty list with an initial element .
pub const fn singleton(head: T) -> Self {
        NonEmpty {
            head,
            tail: Vec::new(),
        }
    }
pub const fn singleton ( head : T ) -> Self { NonEmpty { head , tail : Vec :: new ( ) , } }
Create a new non-empty list with an initial element.
Create a new non - empty list with an initial element .
head
T
head
T