use crate::*;
#[macro_export] macro_rules! command {
    ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
        impl$(<$($l),+>)? Command<$State> for $Command {
            fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
                Ok($handler)
            }
        }
    };
}
pub trait Command<S>: Send + Sync + Sized {
    fn execute (self, state: &mut S) -> Perhaps<Self>;
    fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
        where Self: Sized
    {
        Ok(self.execute(state)?.map(wrap))
    }
}