differential_dataflow/operators/
negate.rs

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1//! Negate the diffs of collections and streams.
2
3use timely::Data;
4use timely::dataflow::{Scope, Stream, StreamCore};
5use timely::dataflow::operators::Map;
6
7use crate::{AsCollection, Collection};
8use crate::difference::Abelian;
9
10/// Negate the contents of a stream.
11pub trait Negate<G, C> {
12    /// Creates a new collection whose counts are the negation of those in the input.
13    ///
14    /// This method is most commonly used with `concat` to get those element in one collection but not another.
15    /// However, differential dataflow computations are still defined for all values of the difference type `R`,
16    /// including negative counts.
17    ///
18    /// # Examples
19    ///
20    /// ```
21    /// use differential_dataflow::input::Input;
22    ///
23    /// ::timely::example(|scope| {
24    ///
25    ///     let data = scope.new_collection_from(1 .. 10).1;
26    ///
27    ///     let odds = data.filter(|x| x % 2 == 1);
28    ///     let evens = data.filter(|x| x % 2 == 0);
29    ///
30    ///     odds.negate()
31    ///         .concat(&data)
32    ///         .assert_eq(&evens);
33    /// });
34    /// ```
35    fn negate(&self) -> Self;
36}
37
38impl<G, D, R, C> Negate<G, C> for Collection<G, D, R, C>
39where
40    G: Scope,
41    C: Clone,
42    StreamCore<G, C>: Negate<G, C>,
43{
44    fn negate(&self) -> Self {
45        self.inner.negate().as_collection()
46    }
47}
48
49impl<G: Scope, D: Data, T: Data, R: Data + Abelian> Negate<G, Vec<(D, T, R)>> for Stream<G, (D, T, R)> {
50    fn negate(&self) -> Self {
51        self.map_in_place(|x| x.2.negate())
52    }
53}
54
differential_dataflow/operators/negate.rs

differential_dataflow/operators/
negate.rs
