filters.rs

pub struct FilterMapInput<F, M>(F, M);

impl<I, T, F: Filter<T>, M: Fn(I) -> T> Filter<I> for FilterMapInput<F, M> {
  fn filter(&self, e: &I) -> bool {
    self.0.filter(self.1(e))
  }
}

pub struct FailableFilterMapErr<F, M>(F, M);

impl <T, EF, EO, F: FailableFilter<T, EF>, M: Fn(EF) -> EO> FailableFilter<T, EO> for FailableFilterMapErr<F, M> {
  fn filter(&self, e: &T) -> Result<bool, EO> {
    self.0.filter(e).map_err(self.1)
  }
}