From 3f9b930c6078def0d39687a32b9d75e666cbde79 Mon Sep 17 00:00:00 2001
From: Susana Quartin <susanaquartin@gmail.com>
Date: Tue, 11 Aug 2020 23:32:50 +0100
Subject: [PATCH] Adds division of TimeDerivative[A] by quantity of A

Fixes #299
---
 .../main/scala/squants/time/TimeDerivative.scala |  8 ++++++++
 .../scala/squants/time/TimeDerivativeSpec.scala  | 16 +++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/shared/src/main/scala/squants/time/TimeDerivative.scala b/shared/src/main/scala/squants/time/TimeDerivative.scala
index 6e22aeed..79ede26f 100644
--- a/shared/src/main/scala/squants/time/TimeDerivative.scala
+++ b/shared/src/main/scala/squants/time/TimeDerivative.scala
@@ -29,6 +29,14 @@ trait TimeDerivative[A <: Quantity[A] with TimeIntegral[_]] {
    * @return
    */
   def *(that: Time): A = timeIntegrated * (that / this.time)
+
+  /**
+   * Returns the portion of quantity change per unit of Time
+   *
+   * @param that The amount of Quantity
+   * @return
+   */
+  def /(that: A): Frequency = (timeIntegrated / that) / time
 }
 
 trait SecondTimeDerivative[A <: SecondTimeIntegral[_]] { self: TimeDerivative[_] ⇒
diff --git a/shared/src/test/scala/squants/time/TimeDerivativeSpec.scala b/shared/src/test/scala/squants/time/TimeDerivativeSpec.scala
index faec6860..4127d989 100644
--- a/shared/src/test/scala/squants/time/TimeDerivativeSpec.scala
+++ b/shared/src/test/scala/squants/time/TimeDerivativeSpec.scala
@@ -9,8 +9,8 @@
 package squants.time
 
 import squants.CustomMatchers
-import squants.motion.UsMilesPerHour
-import squants.space.UsMiles
+import squants.motion.{MetersPerSecond, UsMilesPerHour}
+import squants.space.{Meters, UsMiles}
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
 
@@ -41,6 +41,16 @@ class TimeDerivativeSpec extends AnyFlatSpec with Matchers with CustomMatchers {
 
   it should "satisfy Derivative = Integral * Frequency" in {
     implicit val tolerance = UsMilesPerHour(0.0000000000001)
-    UsMilesPerHour(55) should beApproximately(UsMiles(55) * 1/Hours(1))
+    UsMilesPerHour(55) should beApproximately(UsMiles(55) * 1 / Hours(1))
+  }
+
+  it should "satisfy Frequency = Derivative / Integral (Time value in hours)" in {
+    implicit val tolerance = Hertz(0.0000000000001)
+    Hertz(0.01) should beApproximately(UsMilesPerHour(72) / UsMiles(2))
+  }
+
+  it should "satisfy Frequency = Derivative / Integral (Time value in Seconds)" in {
+    implicit val tolerance = Hertz(0.0000000000001)
+    Hertz(55) should beApproximately(MetersPerSecond(110) / Meters(2))
   }
 }