1 files changed, 19 insertions, 3 deletions
diff --git a/src/volume.rs b/src/volume.rs
index ea78938..087676c 100644
--- a/src/volume.rs
+++ b/src/volume.rs
@@ -1,12 +1,24 @@
 use std::ops::Mul;
 
-trait Volume {
+pub trait Volume {
     /// Returns the volume in SI units (cubic metres).
     fn si(self) -> CubicMetre;
+
+    fn set(&mut self, val: f64);
 }
 
-#[derive(Debug, PartialEq)]
-struct CubicMetre(f64);
+#[derive(Debug, Default, PartialEq)]
+pub struct CubicMetre(f64);
+
+impl Volume for CubicMetre {
+    fn si(self) -> CubicMetre {
+        self
+    }
+
+    fn set(&mut self, val: f64) {
+        self.0 = val;
+    }
+}
 
 #[derive(Debug, PartialEq)]
 struct Litre(f64);
@@ -15,6 +27,10 @@ impl Volume for Litre {
     fn si(self) -> CubicMetre {
         CubicMetre(self.0 * 10_f64.powf(-3.))
     }
+
+    fn set(&mut self, val: f64) {
+        self.0 = val
+    }
 }
 
 impl From<i32> for Litre {