gistfile1.rs

pub type Fun<'a> = Box<FnMut(u8) -> Res<'a> +'a>;

pub enum Res<'a> {
  Done(u8, u8),
  Incomplete(Fun<'a>)
}

pub trait FMap {
  fn fmap<'y,F: Fn(u8) -> u8 + 'y>(&'y mut self, f: F) -> Res<'y>;
}

impl<'z> FMap for Res<'z> {
  fn fmap<'y,F: Fn(u8) -> u8 + 'y>(&'y mut self, f: F) -> Res<'y> {
    match self {
      &mut Res::Incomplete(ref mut g) => {
        Res::Incomplete(Box::new(move |input| {
          let tmp = g(input);
          let res = tmp.fmap(f);
          res
        }))
      },
      &mut Res::Done(i, o) => Res::Done(i,f(o))
    }              
  }                
}
fn main() {

}