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pub trait Semigroup {
fn mappend(self, other: &mut Self) -> Self;
}
pub trait Monoid: Semigroup {
fn mempty() -> Self;
}
impl Semigroup for String {
fn mappend( mut self, other: &mut Self) -> Self {
self.push_str( other);
self
}
}
impl Monoid for String {
fn mempty() -> Self { Self::new()}
}
use std::clone::Clone;
impl<T: Clone> Semigroup for Vec<T> {
fn mappend( mut self, other: &mut Self) -> Self {
self.append( other);
self
}
}
impl<T: Clone> Monoid for Vec<T> {
fn mempty() -> Self { Self::new()}
}