Created input types.

src/cell.rs

@@ -0,0 +1,19 @@
+use core::cell::Cell;
+
+/// Provides a view only reference to a [Cell].
+/// Useful alternative to `&Cell` when an API wants to control where a [Cell]s value can be set.
+#[derive(Copy, Clone)]
+pub struct CellView<'a, T: Copy>(&'a Cell<T>);
+
+impl<T: Copy> CellView<'_, T> {
+    #[inline]
+    pub fn get(self) -> T {
+        self.0.get()
+    }
+}
+
+impl<'a, T: Copy> From<&'a Cell<T>> for CellView<'a, T> {
+    fn from(value: &'a Cell<T>) -> Self {
+        CellView(value)
+    }
+}

src/lib.rs

@@ -1,3 +1,4 @@
 #![no_std]
 
-pub mod transducer;
+pub mod transducer;
+pub mod cell;

src/transducer/input.rs

@@ -0,0 +1,20 @@
+use crate::cell::CellView;
+use crate::transducer::Stateful;
+
+pub struct StatefulInput<'a, T: Copy> {
+    pub state_cell: CellView<'a, T>,
+}
+
+impl<'a, T: Copy> Stateful for StatefulInput<'a, T> {
+    type Value = T;
+
+    #[inline(always)]
+    fn state_cell(&self) -> CellView<'a, Self::Value> {
+        self.state_cell
+    }
+
+    #[inline]
+    fn state(&self) -> Self::Value {
+        self.state_cell.get()
+    }
+}

src/transducer/mod.rs

@@ -1,3 +1,5 @@
+use crate::cell::CellView;
+
 pub mod input;
 pub mod output;
 
@@ -6,5 +8,7 @@ pub mod output;
 pub trait Stateful {
     type Value: Copy;
 
+    fn state_cell(&self) -> CellView<Self::Value>;
+
     fn state(&self) -> Self::Value;
 }