Speed is Length / std::time::Duration.

Author: Jonathan Pallant

src/speed.rs

@@ -1,4 +1,6 @@
 use super::measurement::*;
+use super::Length;
+use std::time::Duration;
 
 /// The `Speed` struct can be used to deal with speeds in a common way.
 /// Common metric and imperial units are supported.
@@ -60,6 +62,16 @@ impl Speed {
     }
 }
 
+impl ::std::ops::Div<Duration> for Length {
+    type Output = Speed;
+
+    fn div(self, rhs: Duration) -> Speed {
+        // It would be useful if Duration had a method that did this...
+        let seconds: f64 = rhs.as_secs() as f64 + ((rhs.subsec_nanos() as f64) * 1e-9);
+        Speed::from_meters_per_second(self.as_meters() / seconds)
+    }
+}
+
 impl Measurement for Speed {
     fn get_base_units(&self) -> f64 {
         self.meters_per_second

src/tests/speed_tests.rs

@@ -1,5 +1,7 @@
 use speed::*;
 use super::assert_almost_eq;
+use std::time::Duration;
+use length::Length;
 
 // Metric
 #[test]
@@ -14,6 +16,16 @@ fn kilometers_per_hour() {
     assert_almost_eq(r2, 27.7777777777);
 }
 
+#[test]
+fn length_over_time() {
+    let l1 = Length::from_meters(3.0);
+    let t1 = Duration::new(1, 500_000_000);
+    let i1 = l1 / t1;
+    let r1 = i1.as_meters_per_second();
+    assert_almost_eq(r1, 2.0);
+}
+
+#[test]
 fn kilometres_per_hour() {
     let i1 = Speed::from_metres_per_second(100.0);
     let r1 = i1.as_kilometres_per_hour();