phenotypes 0.1.2

/// An `Observable` entity is either in a *present* or an *excluded* state
/// in the investigated item.
///
/// For instance, a phenotypic feature such as [Polydactyly](https://hpo.jax.org/browse/term/HP:0010442)
/// can either be present or excluded in the study subject.
pub trait Observable {
    /// Test if the feature was observed in one or more items.
    fn is_present(&self) -> bool;
    /// Test if the feature was not observed in any of the items.
    fn is_excluded(&self) -> bool {
        !self.is_present()
    }
}

/// Common functionalities for containers of [`Observable`] features.
pub trait ObservableFeatures {
    /// The feature.
    type Feature;

    /// Get an iterator over features that were observed in the investigated item.
    fn present_features(&self) -> impl Iterator<Item = &Self::Feature>;
    /// Get the number of observed features.
    fn present_feature_count(&self) -> usize {
        self.present_features().count()
    }

    /// Get an iterator over features whose presence was specifically excluded in the investigated item.
    fn excluded_features(&self) -> impl Iterator<Item = &Self::Feature>;
    /// Get the number of features whose presence was specifically excluded.
    fn excluded_feature_count(&self) -> usize {
        self.excluded_features().count()
    }
}

impl<T> ObservableFeatures for &[T]
where
    T: Observable,
{
    type Feature = T;

    fn present_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_present())
    }

    fn excluded_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_excluded())
    }
}

impl<T, const N: usize> ObservableFeatures for [T; N]
where
    T: Observable,
{
    type Feature = T;

    fn present_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_present())
    }

    fn excluded_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_excluded())
    }
}

impl<T> ObservableFeatures for Vec<T>
where
    T: Observable,
{
    type Feature = T;

    fn present_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_present())
    }

    fn excluded_features(&self) -> impl Iterator<Item = &Self::Feature> {
        self.iter().filter(|&t| t.is_excluded())
    }
}