diff --git a/asparit/src/core/iterator.rs b/asparit/src/core/iterator.rs
index 0494aa4..edc7537 100644
--- a/asparit/src/core/iterator.rs
+++ b/asparit/src/core/iterator.rs
@@ -1,6 +1,6 @@
 use super::{Consumer, IndexedConsumer, IndexedProducerCallback, ProducerCallback, Executor, Reducer};
 
-use crate::inner::{for_each::ForEach, map::Map};
+use crate::inner::{for_each::ForEach, map::Map, map_with::MapWith};
 
 /// Parallel version of the standard iterator trait.
 ///
@@ -96,7 +96,7 @@ pub trait ParallelIterator<'a>: Sized + Send {
         ForEach::new(self, operation)
     }
 
-    /// Applies `map_op` to each item of this iterator, producing a new
+    /// Applies `operation` to each item of this iterator, producing a new
     /// iterator with the results.
     ///
     /// # Examples
@@ -117,6 +117,44 @@ pub trait ParallelIterator<'a>: Sized + Send {
     {
         Map::new(self, operation)
     }
+
+    /// Applies `operation` to the given `init` value with each item of this
+    /// iterator, producing a new iterator with the results.
+    ///
+    /// The `init` value will be cloned only as needed to be paired with
+    /// the group of items in each rayon job.  It does not require the type
+    /// to be `Sync`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::mpsc::channel;
+    /// use rayon::prelude::*;
+    ///
+    /// let (sender, receiver) = channel();
+    ///
+    /// let a: Vec<_> = (0..5)
+    ///                 .into_par_iter()            // iterating over i32
+    ///                 .map_with(sender, |s, x| {
+    ///                     s.send(x).unwrap();     // sending i32 values through the channel
+    ///                     x                       // returning i32
+    ///                 })
+    ///                 .collect();                 // collecting the returned values into a vector
+    ///
+    /// let mut b: Vec<_> = receiver.iter()         // iterating over the values in the channel
+    ///                             .collect();     // and collecting them
+    /// b.sort();
+    ///
+    /// assert_eq!(a, b);
+    /// ```
+    fn map_with<O, T, S>(self, init: S, operation: O) -> MapWith<Self, S, O>
+    where
+        O: Fn(&mut S, Self::Item) -> T + Sync + Send,
+        S: Send + Clone,
+        T: Send,
+    {
+        MapWith::new(self, init, operation)
+    }
 }
 
 /// An iterator that supports "random access" to its data, meaning
diff --git a/asparit/src/inner/for_each.rs b/asparit/src/inner/for_each.rs
index 0de3069..b22e6ee 100644
--- a/asparit/src/inner/for_each.rs
+++ b/asparit/src/inner/for_each.rs
@@ -93,7 +93,7 @@ mod tests {
     async fn test_for_each() {
         let x = (0..10usize)
             .into_par_iter()
-            .map(Some)
+            .map_with(5, |init, item| Some((*init, item)))
             .for_each(|j| {
                 println!("{:?}", j);
             })
diff --git a/asparit/src/inner/map.rs b/asparit/src/inner/map.rs
index 4d9887a..630a144 100644
--- a/asparit/src/inner/map.rs
+++ b/asparit/src/inner/map.rs
@@ -19,7 +19,7 @@ impl<X, O> Map<X, O> {
 impl<'a, X, O, T> ParallelIterator<'a> for Map<X, O>
 where
     X: ParallelIterator<'a>,
-    O: Fn(X::Item) -> T + Sync + Send + Copy + 'a,
+    O: Fn(X::Item) -> T + Clone + Sync + Send + 'a,
     T: Send,
 {
     type Item = O::Output;
@@ -54,7 +54,7 @@ where
 impl<'a, X, O, T> IndexedParallelIterator<'a> for Map<X, O>
 where
     X: IndexedParallelIterator<'a>,
-    O: Fn(X::Item) -> T + Sync + Send + Copy + 'a,
+    O: Fn(X::Item) -> T + Clone + Sync + Send + 'a,
     T: Send,
 {
     fn drive_indexed<E, C, D, R>(self, executor: E, consumer: C) -> E::Result
@@ -94,7 +94,7 @@ struct MapCallback<CB, O> {
 impl<'a, I, O, T, CB> ProducerCallback<'a, I> for MapCallback<CB, O>
 where
     CB: ProducerCallback<'a, T>,
-    O: Fn(I) -> T + Sync + Send + Copy + 'a,
+    O: Fn(I) -> T + Clone + Sync + Send + 'a,
     T: Send,
 {
     type Output = CB::Output;
@@ -115,7 +115,7 @@ where
 impl<'a, I, O, T, CB> IndexedProducerCallback<'a, I> for MapCallback<CB, O>
 where
     CB: IndexedProducerCallback<'a, T>,
-    O: Fn(I) -> T + Sync + Send + Copy + 'a,
+    O: Fn(I) -> T + Clone + Sync + Send + 'a,
     T: Send,
 {
     type Output = CB::Output;
@@ -143,15 +143,14 @@ struct MapProducer<P, O> {
 impl<P, O, T> Producer for MapProducer<P, O>
 where
     P: Producer,
-    O: Fn(P::Item) -> T + Sync + Send + Copy,
+    O: Fn(P::Item) -> T + Clone + Sync + Send,
     T: Send,
 {
     type Item = O::Output;
     type IntoIter = std::iter::Map<P::IntoIter, O>;
 
     fn into_iter(self) -> Self::IntoIter {
-        // self.base.into_iter().map(self.operation)
-        unimplemented!()
+        self.base.into_iter().map(self.operation)
     }
 
     fn split(self) -> (Self, Option<Self>) {
@@ -161,7 +160,7 @@ where
         (
             MapProducer {
                 base: left,
-                operation,
+                operation: operation.clone(),
             },
             right.map(|right| MapProducer {
                 base: right,
@@ -186,7 +185,7 @@ where
 impl<P, O, T> IndexedProducer for MapProducer<P, O>
 where
     P: IndexedProducer,
-    O: Fn(P::Item) -> T + Sync + Send + Copy,
+    O: Fn(P::Item) -> T + Clone + Sync + Send,
     T: Send,
 {
     type Item = O::Output;
@@ -213,17 +212,16 @@ where
     }
 
     fn split_at(self, index: usize) -> (Self, Self) {
-        let operation = self.operation;
         let (left, right) = self.base.split_at(index);
 
         (
             MapProducer {
                 base: left,
-                operation,
+                operation: self.operation.clone(),
             },
             MapProducer {
                 base: right,
-                operation,
+                operation: self.operation,
             },
         )
     }
@@ -257,7 +255,7 @@ impl<C, O> MapConsumer<C, O> {
 impl<I, T, C, O> Consumer<I> for MapConsumer<C, O>
 where
     C: Consumer<O::Output>,
-    O: Fn(I) -> T + Send + Sync + Copy,
+    O: Fn(I) -> T + Clone + Send + Sync,
     T: Send,
 {
     type Folder = MapFolder<C::Folder, O>;
@@ -267,7 +265,7 @@ where
     fn split_off_left(&self) -> (Self, Self::Reducer) {
         let (left, reducer) = self.base.split_off_left();
 
-        (MapConsumer::new(left, self.operation), reducer)
+        (MapConsumer::new(left, self.operation.clone()), reducer)
     }
 
     fn into_folder(self) -> Self::Folder {
@@ -285,14 +283,14 @@ where
 impl<I, T, C, O> IndexedConsumer<I> for MapConsumer<C, O>
 where
     C: IndexedConsumer<O::Output>,
-    O: Fn(I) -> T + Send + Sync + Copy,
+    O: Fn(I) -> T + Clone + Send + Sync,
     T: Send,
 {
     fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
         let (left, right, reducer) = self.base.split_at(index);
 
         (
-            MapConsumer::new(left, self.operation),
+            MapConsumer::new(left, self.operation.clone()),
             MapConsumer::new(right, self.operation),
             reducer,
         )
@@ -309,23 +307,23 @@ struct MapFolder<F, O> {
 impl<I, T, F, O> Folder<I> for MapFolder<F, O>
 where
     F: Folder<O::Output>,
-    O: Fn(I) -> T + Copy,
+    O: Fn(I) -> T + Clone,
 {
     type Result = F::Result;
 
-    fn consume(self, item: I) -> Self {
+    fn consume(mut self, item: I) -> Self {
         let mapped_item = (self.operation)(item);
-        MapFolder {
-            base: self.base.consume(mapped_item),
-            operation: self.operation,
-        }
+
+        self.base = self.base.consume(mapped_item);
+
+        self
     }
 
     fn consume_iter<X>(mut self, iter: X) -> Self
     where
         X: IntoIterator<Item = I>,
     {
-        self.base = self.base.consume_iter(iter.into_iter().map(self.operation));
+        self.base = self.base.consume_iter(iter.into_iter().map(self.operation.clone()));
 
         self
     }
diff --git a/asparit/src/inner/map_with.rs b/asparit/src/inner/map_with.rs
new file mode 100644
index 0000000..db3df76
--- /dev/null
+++ b/asparit/src/inner/map_with.rs
@@ -0,0 +1,422 @@
+use crate::{
+    Consumer, Folder, IndexedConsumer, IndexedParallelIterator, IndexedProducer, Reducer,
+    IndexedProducerCallback, ParallelIterator, Producer, ProducerCallback, Executor,
+};
+
+/* MapWith */
+
+pub struct MapWith<X, S, O> {
+    base: X,
+    item: S,
+    operation: O,
+}
+
+impl<X, S, O> MapWith<X, S, O> {
+    pub fn new(base: X, item: S, operation: O) -> Self {
+        Self { base, item, operation }
+    }
+}
+
+impl<'a, X, O, T, S> ParallelIterator<'a> for MapWith<X, S, O>
+where
+    X: ParallelIterator<'a>,
+    O: Fn(&mut S, X::Item) -> T + Clone + Sync + Send + 'a,
+    T: Send,
+    S: Clone + Send + 'a,
+{
+    type Item = T;
+
+    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,
+    {
+        let consumer = MapWithConsumer::new(consumer, self.item, self.operation);
+
+        self.base.drive(executor, consumer)
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<'a, Self::Item>,
+    {
+        self.base.with_producer(MapWithCallback {
+            callback,
+            item: self.item,
+            operation: self.operation,
+        })
+    }
+
+    fn len_hint_opt(&self) -> Option<usize> {
+        self.base.len_hint_opt()
+    }
+}
+
+impl<'a, X, O, T, S> IndexedParallelIterator<'a> for MapWith<X, S, O>
+where
+    X: IndexedParallelIterator<'a>,
+    O: Fn(&mut S, X::Item) -> T + Clone + Sync + Send + 'a,
+    T: Send,
+    S: Clone + Send + 'a,
+{
+    fn drive_indexed<E, C, D, R>(self, executor: E, consumer: C) -> E::Result
+    where
+        E: Executor<'a, D>,
+        C: IndexedConsumer<Self::Item, Result = D, Reducer = R>,
+        D: Send,
+        R: Reducer<D>
+    {
+        let consumer = MapWithConsumer::new(consumer, self.item, self.operation);
+
+        self.base.drive_indexed(executor, consumer)
+    }
+
+    fn with_producer_indexed<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: IndexedProducerCallback<'a, Self::Item>,
+    {
+        self.base.with_producer_indexed(MapWithCallback {
+            callback,
+            item: self.item,
+            operation: self.operation,
+        })
+    }
+
+    fn len_hint(&self) -> usize {
+        self.base.len_hint()
+    }
+}
+
+/* MapWithCallback */
+
+struct MapWithCallback<CB, S, O> {
+    callback: CB,
+    item: S,
+    operation: O,
+}
+
+impl<'a, I, S, O, T, CB> ProducerCallback<'a, I> for MapWithCallback<CB, S, O>
+where
+    CB: ProducerCallback<'a, T>,
+    O: Fn(&mut S, I) -> T + Clone + Sync + Send + 'a,
+    T: Send,
+    S: Clone + Send + 'a,
+{
+    type Output = CB::Output;
+
+    fn callback<P>(self, base: P) -> CB::Output
+    where
+        P: Producer<Item = I> + 'a,
+    {
+        let producer = MapWithProducer {
+            base,
+            item: self.item,
+            operation: self.operation,
+        };
+
+        self.callback.callback(producer)
+    }
+}
+
+impl<'a, I, S, O, T, CB> IndexedProducerCallback<'a, I> for MapWithCallback<CB, S, O>
+where
+    CB: IndexedProducerCallback<'a, T>,
+    O: Fn(&mut S, I) -> T + Clone + Sync + Send + 'a,
+    T: Send,
+    S: Clone + Send + 'a,
+{
+    type Output = CB::Output;
+
+    fn callback<P>(self, base: P) -> CB::Output
+    where
+        P: IndexedProducer<Item = I> + 'a,
+    {
+        let producer = MapWithProducer {
+            base,
+            item: self.item,
+            operation: self.operation,
+        };
+
+        self.callback.callback(producer)
+    }
+}
+
+/* MapWithProducer */
+
+struct MapWithProducer<P, S, O> {
+    base: P,
+    item: S,
+    operation: O,
+}
+
+impl<P, S, O, T> Producer for MapWithProducer<P, S, O>
+where
+    P: Producer,
+    O: Fn(&mut S, P::Item) -> T + Clone + Sync + Send,
+    T: Send,
+    S: Clone + Send,
+{
+    type Item = T;
+    type IntoIter = MapWithIter<P::IntoIter, S, O>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        MapWithIter {
+            base: self.base.into_iter(),
+            item: self.item,
+            operation: self.operation,
+        }
+    }
+
+    fn split(self) -> (Self, Option<Self>) {
+        let item = self.item;
+        let operation = self.operation;
+        let (left, right) = self.base.split();
+
+        (
+            MapWithProducer {
+                base: left,
+                item: item.clone(),
+                operation: operation.clone(),
+            },
+            right.map(|right| MapWithProducer {
+                base: right,
+                item,
+                operation,
+            }),
+        )
+    }
+
+    fn fold_with<G>(self, folder: G) -> G
+    where
+        G: Folder<Self::Item>,
+    {
+        let folder = MapWithFolder {
+            base: folder,
+            item: self.item,
+            operation: self.operation,
+        };
+
+        self.base.fold_with(folder).base
+    }
+}
+
+impl<P, S, O, T> IndexedProducer for MapWithProducer<P, S, O>
+where
+    P: IndexedProducer,
+    O: Fn(&mut S, P::Item) -> T + Clone + Sync + Send,
+    T: Send,
+    S: Clone + Send,
+{
+    type Item = T;
+    type IntoIter = MapWithIter<P::IntoIter, S, O>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        MapWithIter {
+            base: self.base.into_iter(),
+            item: self.item,
+            operation: self.operation,
+        }
+    }
+
+    fn splits(&self) -> Option<usize> {
+        self.base.splits()
+    }
+
+    fn len(&self) -> usize {
+        self.base.len()
+    }
+
+    fn min_len(&self) -> Option<usize> {
+        self.base.min_len()
+    }
+
+    fn max_len(&self) -> Option<usize> {
+        self.base.max_len()
+    }
+
+    fn split_at(self, index: usize) -> (Self, Self) {
+        let (left, right) = self.base.split_at(index);
+
+        (
+            MapWithProducer {
+                base: left,
+                item: self.item.clone(),
+                operation: self.operation.clone(),
+            },
+            MapWithProducer {
+                base: right,
+                item: self.item,
+                operation: self.operation,
+            },
+        )
+    }
+
+    fn fold_with<G>(self, folder: G) -> G
+    where
+        G: Folder<Self::Item>,
+    {
+        let folder = MapWithFolder {
+            base: folder,
+            item: self.item,
+            operation: self.operation,
+        };
+
+        self.base.fold_with(folder).base
+    }
+}
+
+/* MapWithIter */
+
+struct MapWithIter<I, S, O> {
+    base: I,
+    item: S,
+    operation: O,
+}
+
+impl<I, S, O, T> Iterator for MapWithIter<I, S, O>
+where
+    I: Iterator,
+    O: Fn(&mut S, I::Item) -> T,
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        let item = self.base.next()?;
+
+        Some((self.operation)(&mut self.item, item))
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.base.size_hint()
+    }
+}
+
+impl<I, S, O, T> DoubleEndedIterator for MapWithIter<I, S, O>
+where
+    I: DoubleEndedIterator,
+    O: Fn(&mut S, I::Item) -> T,
+{
+    fn next_back(&mut self) -> Option<T> {
+        let item = self.base.next_back()?;
+
+        Some((self.operation)(&mut self.item, item))
+    }
+}
+
+impl<I, S, O, T> ExactSizeIterator for MapWithIter<I, S, O>
+where
+    I: ExactSizeIterator,
+    O: Fn(&mut S, I::Item) -> T,
+{ }
+
+/* MapWithConsumer */
+
+struct MapWithConsumer<C, S, O> {
+    base: C,
+    item: S,
+    operation: O,
+}
+
+impl<C, S, O> MapWithConsumer<C, S, O> {
+    fn new(base: C, item: S, operation: O) -> Self {
+        Self { base, item, operation }
+    }
+}
+
+impl<I, T, C, S, O> Consumer<I> for MapWithConsumer<C, S, O>
+where
+    C: Consumer<T>,
+    O: Fn(&mut S, I) -> T + Clone + Send + Sync,
+    T: Send,
+    S: Clone + Send,
+{
+    type Folder = MapWithFolder<C::Folder, S, O>;
+    type Reducer = C::Reducer;
+    type Result = C::Result;
+
+    fn split_off_left(&self) -> (Self, Self::Reducer) {
+        let (left, reducer) = self.base.split_off_left();
+
+        (MapWithConsumer::new(left, self.item.clone(), self.operation.clone()), reducer)
+    }
+
+    fn into_folder(self) -> Self::Folder {
+        MapWithFolder {
+            base: self.base.into_folder(),
+            item: self.item,
+            operation: self.operation,
+        }
+    }
+
+    fn is_full(&self) -> bool {
+        self.base.is_full()
+    }
+}
+
+impl<I, T, C, S, O> IndexedConsumer<I> for MapWithConsumer<C, S, O>
+where
+    C: IndexedConsumer<T>,
+    O: Fn(&mut S, I) -> T + Clone + Send + Sync,
+    T: Send,
+    S: Clone + Send,
+{
+    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
+        let (left, right, reducer) = self.base.split_at(index);
+
+        (
+            MapWithConsumer::new(left, self.item.clone(), self.operation.clone()),
+            MapWithConsumer::new(right, self.item, self.operation),
+            reducer,
+        )
+    }
+}
+
+/* MapWithFolder */
+
+struct MapWithFolder<F, S, O> {
+    base: F,
+    item: S,
+    operation: O,
+}
+
+impl<I, T, F, S, O> Folder<I> for MapWithFolder<F, S, O>
+where
+    F: Folder<T>,
+    O: Fn(&mut S, I) -> T + Clone,
+{
+    type Result = F::Result;
+
+    fn consume(mut self, item: I) -> Self {
+        let mapped_item = (self.operation)(&mut self.item, item);
+
+        self.base = self.base.consume(mapped_item);
+
+        self
+    }
+
+    fn consume_iter<X>(mut self, iter: X) -> Self
+    where
+        X: IntoIterator<Item = I>,
+    {
+        fn with<'f, I, S, T>(item: &'f mut S, operation: impl Fn(&mut S, I) -> T + 'f,
+        ) -> impl FnMut(I) -> T + 'f {
+            move |x| operation(item, x)
+        }
+
+        let mapped_iter = iter.into_iter().map(with(&mut self.item, self.operation.clone()));
+
+        self.base = self.base.consume_iter(mapped_iter);
+
+        self
+    }
+
+    fn complete(self) -> F::Result {
+        self.base.complete()
+    }
+
+    fn is_full(&self) -> bool {
+        self.base.is_full()
+    }
+}
diff --git a/asparit/src/inner/mod.rs b/asparit/src/inner/mod.rs
index c913c54..f2055fa 100644
--- a/asparit/src/inner/mod.rs
+++ b/asparit/src/inner/mod.rs
@@ -1,3 +1,4 @@
 pub mod for_each;
 pub mod map;
 pub mod noop;
+pub mod map_with;