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//! Extension methods for `StreamVec` based on record-by-record transformation.
use crate::dataflow::StreamVec;
use crate::progress::Timestamp;
use crate::dataflow::channels::pact::Pipeline;
use crate::dataflow::operators::generic::operator::Operator;
use crate::dataflow::operators::core::{Map as MapCore};
/// Extension trait for `StreamVec`.
pub trait Map<'scope, T: Timestamp, D: 'static> : Sized {
/// Consumes each element of the stream and yields a new element.
///
/// # Examples
/// ```
/// use timely::dataflow::operators::{ToStream, Inspect, vec::Map};
///
/// timely::example(|scope| {
/// (0..10).to_stream(scope)
/// .map(|x| x + 1)
/// .inspect(|x| println!("seen: {:?}", x));
/// });
/// ```
fn map<D2: 'static, L: FnMut(D)->D2+'static>(self, mut logic: L) -> StreamVec<'scope, T, D2> {
self.flat_map(move |x| std::iter::once(logic(x)))
}
/// Updates each element of the stream and yields the element, re-using memory where possible.
///
/// # Examples
/// ```
/// use timely::dataflow::operators::{ToStream, Inspect, vec::Map};
///
/// timely::example(|scope| {
/// (0..10).to_stream(scope)
/// .map_in_place(|x| *x += 1)
/// .inspect(|x| println!("seen: {:?}", x));
/// });
/// ```
fn map_in_place<L: FnMut(&mut D)+'static>(self, logic: L) -> StreamVec<'scope, T, D>;
/// Consumes each element of the stream and yields some number of new elements.
///
/// # Examples
/// ```
/// use timely::dataflow::operators::{ToStream, Inspect, vec::Map};
///
/// timely::example(|scope| {
/// (0..10).to_stream(scope)
/// .flat_map(|x| (0..x))
/// .inspect(|x| println!("seen: {:?}", x));
/// });
/// ```
fn flat_map<I: IntoIterator, L: FnMut(D)->I+'static>(self, logic: L) -> StreamVec<'scope, T, I::Item> where I::Item: 'static;
}
impl<'scope, T: Timestamp, D: 'static> Map<'scope, T, D> for StreamVec<'scope, T, D> {
fn map_in_place<L: FnMut(&mut D)+'static>(self, mut logic: L) -> StreamVec<'scope, T, D> {
self.unary(Pipeline, "MapInPlace", move |_,_| move |input, output| {
input.for_each_time(|time, data| {
let mut session = output.session(&time);
for data in data {
for datum in data.iter_mut() { logic(datum); }
session.give_container(data);
}
})
})
}
// TODO : This would be more robust if it captured an iterator and then pulled an appropriate
// TODO : number of elements from the iterator. This would allow iterators that produce many
// TODO : records without taking arbitrarily long and arbitrarily much memory.
fn flat_map<I: IntoIterator, L: FnMut(D)->I+'static>(self, logic: L) -> StreamVec<'scope, T, I::Item> where I::Item: 'static {
MapCore::flat_map(self, logic)
}
}