Implemented 'filter' operation

asparit/src/core/iterator.rs

@@ -7,6 +7,7 @@ use crate::{
         cloned::Cloned,
         collect::Collect,
         copied::Copied,
+        filter::Filter,
         for_each::ForEach,
         inspect::Inspect,
         map::Map,
@@ -493,6 +494,27 @@ pub trait ParallelIterator<'a>: Sized + Send {
         Update::new(self, operation)
     }
 
+    /// Applies `operation` to each item of this iterator, producing a new
+    /// iterator with only the items that gave `true` results.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    ///
+    /// let mut par_iter = (0..10).into_par_iter().filter(|x| x % 2 == 0);
+    ///
+    /// let even_numbers: Vec<_> = par_iter.collect();
+    ///
+    /// assert_eq!(&even_numbers[..], &[0, 2, 4, 6, 8]);
+    /// ```
+    fn filter<O>(self, operation: O) -> Filter<Self, O>
+    where
+        O: Fn(&Self::Item) -> bool + Clone + Send + 'a,
+    {
+        Filter::new(self, operation)
+    }
+
     /// Reduces the items in the iterator into one item using `operation`.
     /// The argument `identity` should be a closure that can produce
     /// "identity" value which may be inserted into the sequence as

asparit/src/inner/filter.rs

@@ -0,0 +1,229 @@
+use crate::{Consumer, Executor, Folder, ParallelIterator, Producer, ProducerCallback, Reducer};
+
+/* Filter */
+
+pub struct Filter<X, O> {
+    base: X,
+    operation: O,
+}
+
+impl<X, O> Filter<X, O> {
+    pub fn new(base: X, operation: O) -> Self {
+        Self { base, operation }
+    }
+}
+
+impl<'a, X, O> ParallelIterator<'a> for Filter<X, O>
+where
+    X: ParallelIterator<'a>,
+    O: Fn(&X::Item) -> bool + Clone + Send + 'a,
+{
+    type Item = X::Item;
+
+    fn drive<E, C, D, R>(self, executor: E, consumer: C) -> E::Result
+    where
+        E: Executor<'a, D>,
+        C: Consumer<Self::Item, Result = D, Reducer = R> + 'a,
+        D: Send,
+        R: Reducer<D> + Send,
+    {
+        self.base.drive(
+            executor,
+            FilterConsumer {
+                base: consumer,
+                operation: self.operation,
+            },
+        )
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<'a, Self::Item>,
+    {
+        self.base.with_producer(FilterCallback {
+            base: callback,
+            operation: self.operation,
+        })
+    }
+
+    fn len_hint_opt(&self) -> Option<usize> {
+        self.base.len_hint_opt()
+    }
+}
+
+/* FilterConsumer */
+
+struct FilterConsumer<C, O> {
+    base: C,
+    operation: O,
+}
+
+impl<'a, C, O, T> Consumer<T> for FilterConsumer<C, O>
+where
+    C: Consumer<T>,
+    O: Fn(&T) -> bool + Clone + Send,
+{
+    type Folder = FilterFolder<C::Folder, O>;
+    type Reducer = C::Reducer;
+    type Result = C::Result;
+
+    fn split(self) -> (Self, Self, Self::Reducer) {
+        let (left, right, reducer) = self.base.split();
+
+        let left = FilterConsumer {
+            base: left,
+            operation: self.operation.clone(),
+        };
+        let right = FilterConsumer {
+            base: right,
+            operation: self.operation,
+        };
+
+        (left, right, reducer)
+    }
+
+    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
+        let (left, right, reducer) = self.base.split_at(index);
+
+        let left = FilterConsumer {
+            base: left,
+            operation: self.operation.clone(),
+        };
+        let right = FilterConsumer {
+            base: right,
+            operation: self.operation,
+        };
+
+        (left, right, reducer)
+    }
+
+    fn into_folder(self) -> Self::Folder {
+        FilterFolder {
+            base: self.base.into_folder(),
+            operation: self.operation,
+        }
+    }
+
+    fn is_full(&self) -> bool {
+        self.base.is_full()
+    }
+}
+
+/* FilterFolder */
+
+struct FilterFolder<F, O> {
+    base: F,
+    operation: O,
+}
+
+impl<F, O, T> Folder<T> for FilterFolder<F, O>
+where
+    F: Folder<T>,
+    O: Fn(&T) -> bool + Clone,
+{
+    type Result = F::Result;
+
+    fn consume(mut self, item: T) -> Self {
+        (self.operation)(&item);
+
+        self.base = self.base.consume(item);
+
+        self
+    }
+
+    fn consume_iter<X>(mut self, iter: X) -> Self
+    where
+        X: IntoIterator<Item = T>,
+    {
+        self.base = self
+            .base
+            .consume_iter(iter.into_iter().filter(self.operation.clone()));
+
+        self
+    }
+
+    fn complete(self) -> Self::Result {
+        self.base.complete()
+    }
+
+    fn is_full(&self) -> bool {
+        self.base.is_full()
+    }
+}
+
+/* FilterCallback */
+
+struct FilterCallback<CB, O> {
+    base: CB,
+    operation: O,
+}
+
+impl<'a, CB, O, T> ProducerCallback<'a, T> for FilterCallback<CB, O>
+where
+    CB: ProducerCallback<'a, T>,
+    O: Fn(&T) -> bool + Clone + Send + 'a,
+{
+    type Output = CB::Output;
+
+    fn callback<P>(self, producer: P) -> Self::Output
+    where
+        P: Producer<Item = T> + 'a,
+    {
+        self.base.callback(FilterProducer {
+            base: producer,
+            operation: self.operation,
+        })
+    }
+}
+
+/* FilterProducer */
+
+struct FilterProducer<P, O> {
+    base: P,
+    operation: O,
+}
+
+impl<'a, P, O, T> Producer for FilterProducer<P, O>
+where
+    P: Producer<Item = T>,
+    O: Fn(&T) -> bool + Clone + Send,
+{
+    type Item = T;
+    type IntoIter = std::iter::Filter<P::IntoIter, O>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.base.into_iter().filter(self.operation)
+    }
+
+    fn split(self) -> (Self, Option<Self>) {
+        let operation = self.operation;
+        let (left, right) = self.base.split();
+
+        let left = FilterProducer {
+            base: left,
+            operation: operation.clone(),
+        };
+        let right = right.map(move |right| FilterProducer {
+            base: right,
+            operation,
+        });
+
+        (left, right)
+    }
+
+    fn splits(&self) -> Option<usize> {
+        self.base.splits()
+    }
+
+    fn fold_with<F>(self, folder: F) -> F
+    where
+        F: Folder<Self::Item>,
+    {
+        self.base
+            .fold_with(FilterFolder {
+                base: folder,
+                operation: self.operation,
+            })
+            .base
+    }
+}

asparit/src/inner/mod.rs

@@ -1,6 +1,7 @@
 pub mod cloned;
 pub mod collect;
 pub mod copied;
+pub mod filter;
 pub mod for_each;
 pub mod inspect;
 pub mod map;
@@ -39,12 +40,13 @@ mod tests {
             .update(|x| x.push(5))
             .map_init(
                 move || i.fetch_add(1, Ordering::Relaxed),
-                |init, item| Some((*init, item)),
+                |init, item| (item, *init),
             )
+            .filter(|(_, i)| i % 2 == 0)
             .try_for_each_init(
                 move || j.fetch_add(1, Ordering::Relaxed),
-                |init, item| -> Result<(), ()> {
-                    println!("{:?} {:?}", init, item);
+                |item, init| -> Result<(), ()> {
+                    println!("{:?} - {:?}", item, init);
 
                     Ok(())
                 },