indicator 0.1.5

Abstractions for stream aggregation, we call them `Indicator` s.
Documentation 
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/// Then combinator.
pub mod then;

/// Facet combinator.
pub mod facet;

/// Map operator.
pub mod map;

pub use facet::{facet, Facet};
pub use map::{map, Map};
use then::Then;

#[cfg(feature = "std")]
pub use facet::{facet_map, FacetMap};

/// Operator.
pub trait Operator<I> {
    /// Output type.
    type Output;

    /// Produce the next output.
    fn next(&mut self, input: I) -> Self::Output;
}

/// Operator extension trait.
pub trait OperatorExt<I>: Operator<I> {
    /// Combine with another operator that uses `Self::Output` as input type.
    ///
    /// The result operator will perform the `other` operator after performing the `self`.
    fn then<P2>(self, other: P2) -> Then<I, Self, P2>
    where
        Self: Sized,
        P2: Operator<Self::Output>,
    {
        Then(self, other, core::marker::PhantomData::default())
    }

    /// Combine with another operator with the same input type.
    ///
    /// The result operator will perform two operators simultaneously.
    fn facet<P2>(self, other: P2) -> Facet<I, Self, P2>
    where
        Self: Sized,
        P2: Operator<I>,
    {
        facet(self, other)
    }

    /// Map the output after performing the operator.
    fn map<O, F>(self, f: F) -> Then<I, Self, Map<F>>
    where
        Self: Sized,
        F: FnMut(Self::Output) -> O,
    {
        self.then(map(f))
    }
}

impl<I, T: Operator<I>> OperatorExt<I> for T {}