Implement num::Zero.

Part of iliekturtles#26.
radix · Dec 23, 2017 · d7f38bd · d7f38bd
1 parent e05dab3
commit d7f38bd
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diff --git a/src/system.rs b/src/system.rs
@@ -839,6 +839,25 @@ macro_rules! system {
             }
         }
 
+        impl<D, U, V> $crate::num::Zero for Quantity<D, U, V>
+        where
+            D: Dimension + ?Sized,
+            U: Units<V> + ?Sized,
+            V: $crate::num::Num + $crate::Conversion<V>,
+        {
+            fn zero() -> Self {
+                Quantity {
+                    dimension: $crate::lib::marker::PhantomData,
+                    units: $crate::lib::marker::PhantomData,
+                    value: V::zero(),
+                }
+            }
+
+            fn is_zero(&self) -> bool {
+                self.value.is_zero()
+            }
+        }
+
         /// Macro to implement [`quantity`](si/struct.Quantity.html) type aliases for a specific
         /// [system of units][units] and value storage type.
         ///

diff --git a/src/tests.rs b/src/tests.rs
@@ -387,6 +387,14 @@ mod system_macro {
 
         Q!(tests, V);
 
+        #[test]
+        fn zero() {
+            let z = Length::zero();
+
+            Test::assert_eq(z.value, 0.0);
+            assert!(z.is_zero());
+        }
+
         quickcheck! {
             #[allow(trivial_casts)]
             fn from_base(v: A<V>) -> bool