Created input types.

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()
+    }
+}