1 files changed, 32 insertions, 1 deletions
diff --git a/src/volume.rs b/src/volume.rs
index 087676c..feeae14 100644
--- a/src/volume.rs
+++ b/src/volume.rs
@@ -1,10 +1,33 @@
-use std::ops::Mul;
+use std::{
+    fmt::{self, Display, Formatter},
+    ops::Mul,
+};
 
 pub trait Volume {
     /// Returns the volume in SI units (cubic metres).
     fn si(self) -> CubicMetre;
 
     fn set(&mut self, val: f64);
+
+    fn unit(&self) -> VolumeUnit;
+}
+
+pub enum VolumeUnit {
+    CubicMetre,
+    Litre,
+}
+
+impl Display for VolumeUnit {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}",
+            match self {
+                Self::CubicMetre => "m³",
+                Self::Litre => "L",
+            }
+        )
+    }
 }
 
 #[derive(Debug, Default, PartialEq)]
@@ -18,6 +41,10 @@ impl Volume for CubicMetre {
     fn set(&mut self, val: f64) {
         self.0 = val;
     }
+
+    fn unit(&self) -> VolumeUnit {
+        VolumeUnit::CubicMetre
+    }
 }
 
 #[derive(Debug, PartialEq)]
@@ -31,6 +58,10 @@ impl Volume for Litre {
     fn set(&mut self, val: f64) {
         self.0 = val
     }
+
+    fn unit(&self) -> VolumeUnit {
+        VolumeUnit::Litre
+    }
 }
 
 impl From<i32> for Litre {