diff --git a/src/func.rs b/src/func.rs
index 41a38a0..1769e26 100644
--- a/src/func.rs
+++ b/src/func.rs
@@ -257,3 +257,17 @@ pub trait MonadFailOver<T: Monad>: MonadFailAny {
         Self: 'a,
         T: 'a;
 }
+
+pub trait SharedFunctor: WeakFunctor {
+    type Shared<'a, A: 'a + Clone>: 'a + Clone
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
+    where
+        Self: 'a;
+
+    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
+    where
+        Self: 'a;
+}
diff --git a/src/func/classes/composition.rs b/src/func/classes/composition.rs
index 54d9683..8ae9645 100644
--- a/src/func/classes/composition.rs
+++ b/src/func/classes/composition.rs
@@ -124,7 +124,8 @@ impl<U: Monad, V: Monad + LocalFunctor> Monad for CompositionClass<U, V> {
 impl<E, U: Monad, V: MonadFail<E> + LocalFunctor> MonadFail<E> for CompositionClass<U, V> {
     fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
     where
-        Self: 'a {
+        Self: 'a,
+    {
         U::pure(V::fail(e))
     }
 }
diff --git a/src/func/classes/future.rs b/src/func/classes/future.rs
index 907ab6d..ffe43de 100644
--- a/src/func/classes/future.rs
+++ b/src/func/classes/future.rs
@@ -5,7 +5,7 @@
 
 use std::{future::Future, pin::Pin};
 
-use futures::join;
+use futures::{future::Shared, join, FutureExt};
 
 use crate::func::*;
 
@@ -107,3 +107,23 @@ impl Monad for FutureClass {
         Box::pin(async { ffa.await.await })
     }
 }
+
+impl SharedFunctor for FutureClass {
+    type Shared<'a, A: 'a + Clone> = Shared<Pin<Box<dyn 'a + Future<Output = A>>>>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
+    where
+        Self: 'a,
+    {
+        fa.shared()
+    }
+
+    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
+    where
+        Self: 'a,
+    {
+        Box::pin(sa)
+    }
+}
diff --git a/src/func/classes/option.rs b/src/func/classes/option.rs
index 7758b95..a379ae4 100644
--- a/src/func/classes/option.rs
+++ b/src/func/classes/option.rs
@@ -175,3 +175,23 @@ mod option_tests {
         test_suite::monad_follows_laws::<T>().unwrap();
     }
 }
+
+impl SharedFunctor for OptionClass {
+    type Shared<'a, A: 'a + Clone> = Self::F<'a, A>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
+    where
+        Self: 'a,
+    {
+        fa
+    }
+
+    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
+    where
+        Self: 'a,
+    {
+        sa
+    }
+}
diff --git a/src/func/classes/result.rs b/src/func/classes/result.rs
index 854c407..e8bd56b 100644
--- a/src/func/classes/result.rs
+++ b/src/func/classes/result.rs
@@ -213,3 +213,23 @@ impl<T: Monad> MonadFailOver<T> for ResultFailOver<T> {
         fa
     }
 }
+
+impl<E: Clone> SharedFunctor for ResultClass<E> {
+    type Shared<'a, A: 'a + Clone> = Self::F<'a, A>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
+    where
+        Self: 'a,
+    {
+        fa
+    }
+
+    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
+    where
+        Self: 'a,
+    {
+        sa
+    }
+}
diff --git a/src/func/classes/solo.rs b/src/func/classes/solo.rs
index a3989bc..dfaf8e7 100644
--- a/src/func/classes/solo.rs
+++ b/src/func/classes/solo.rs
@@ -114,3 +114,23 @@ impl LocalFunctor for SoloClass {
         fa
     }
 }
+
+impl SharedFunctor for SoloClass {
+    type Shared<'a, A: 'a + Clone> = Self::F<'a, A>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
+    where
+        Self: 'a,
+    {
+        fa
+    }
+
+    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
+    where
+        Self: 'a,
+    {
+        sa
+    }
+}
diff --git a/src/std.rs b/src/std.rs
index 30fa0ac..4c517cb 100644
--- a/src/std.rs
+++ b/src/std.rs
@@ -37,7 +37,7 @@ impl<S: Serializable> ExtSerializable for S {
 }
 
 /// Extention trait for simpler conversion between [`Context::T`] and [`Context::Fallible`].
-/// 
+///
 /// Until either Rust type system or [`crate::func`] take serious changes,
 /// this is the preferred way to switch between [Wrapped] and [fallible].
 pub trait FallibleContext: Context {
diff --git a/src/std/atomic/boolean.rs b/src/std/atomic/boolean.rs
index 019e01e..3b590e4 100644
--- a/src/std/atomic/boolean.rs
+++ b/src/std/atomic/boolean.rs
@@ -80,8 +80,14 @@ mod tests {
 
     #[test]
     fn cannot_parse_out_of_bound_value() {
-        assert_eq!(bool::parse_slice(&[2]).unwrap_err(), BooleanParseError::OutOfBounds(2));
-        assert_eq!(bool::parse_slice(&[2, 0]).unwrap_err(), BooleanParseError::OutOfBounds(2));
+        assert_eq!(
+            bool::parse_slice(&[2]).unwrap_err(),
+            BooleanParseError::OutOfBounds(2)
+        );
+        assert_eq!(
+            bool::parse_slice(&[2, 0]).unwrap_err(),
+            BooleanParseError::OutOfBounds(2)
+        );
     }
 
     #[test]
@@ -91,6 +97,9 @@ mod tests {
 
     #[test]
     fn cannot_parse_extra_tail() {
-        assert_eq!(bool::parse_slice(&[0, 10, 20, 30]).unwrap_err(), BooleanParseError::ExtraData(3));
+        assert_eq!(
+            bool::parse_slice(&[0, 10, 20, 30]).unwrap_err(),
+            BooleanParseError::ExtraData(3)
+        );
     }
 }
diff --git a/src/std/collections/rbtree.rs b/src/std/collections/rbtree.rs
index 3648ddb..67f0a34 100644
--- a/src/std/collections/rbtree.rs
+++ b/src/std/collections/rbtree.rs
@@ -1,6 +1,6 @@
 pub mod subset;
 
-use std::{rc::Rc, error::Error, fmt::Display};
+use std::{error::Error, fmt::Display, rc::Rc};
 
 use crate::core::*;
 use crate::std::{
@@ -224,7 +224,8 @@ impl<'a, Ctx: 'a + Context, F: Factory<'a, Ctx>> Factory<'a, Ctx> for BFactory<F
         let key = self
             .key_factory
             .deserialize(deserializer, resolver, addresses)
-            .map_err(TreeParseError::Key)?.into();
+            .map_err(TreeParseError::Key)?
+            .into();
         Ok(BNode { cl, cr, key })
     }
 
@@ -252,7 +253,8 @@ impl<'a, Ctx: 'a + Context, F: Factory<'a, Ctx>> Factory<'a, Ctx> for RFactory<F
         let key = self
             .key_factory
             .deserialize(deserializer, resolver, addresses)
-            .map_err(TreeParseError::Key)?.into();
+            .map_err(TreeParseError::Key)?
+            .into();
         Ok(RNode { cl, cr, key })
     }