add ElectricFieldStrength, implement ElectricPotential unimplemented method

shared/src/main/scala/squants/electro/ElectricFieldStrength.scala

@@ -0,0 +1,48 @@
+package squants.electro
+
+import squants.space.{Length, Meters}
+import squants.{AbstractQuantityNumeric, Dimension, PrimaryUnit, Quantity, SiUnit, UnitConverter, UnitOfMeasure}
+
+/**
+  *
+  * @author Nicolas Vinuesa
+  * @since 1.4
+  *
+  * @param value Double
+  */
+final class ElectricFieldStrength private (val value: Double, val unit: ElectricFieldStrengthUnit)
+  extends Quantity[ElectricFieldStrength] {
+
+  def dimension = ElectricFieldStrength
+
+  def *(that: Length): ElectricPotential = Volts(this.toVoltsPerMeter * that.toMeters)
+
+  def toVoltsPerMeter = to(VoltsPerMeter)
+}
+
+object ElectricFieldStrength extends Dimension[ElectricFieldStrength] {
+  private[electro] def apply[A](n: A, unit: ElectricFieldStrengthUnit)(implicit num: Numeric[A]) = new ElectricFieldStrength(num.toDouble(n), unit)
+  def apply = parse _
+  def name = "ElectricFieldStrength"
+  def primaryUnit = VoltsPerMeter
+  def siUnit = VoltsPerMeter
+  def units = Set(VoltsPerMeter)
+}
+
+trait ElectricFieldStrengthUnit extends UnitOfMeasure[ElectricFieldStrength] with UnitConverter {
+  def apply[A](n: A)(implicit num: Numeric[A]) = ElectricFieldStrength(n, this)
+}
+
+object VoltsPerMeter extends ElectricFieldStrengthUnit with PrimaryUnit with SiUnit {
+  val symbol = Volts.symbol + "/" + Meters.symbol
+}
+
+object ElectricFieldStrengthConversions {
+  lazy val voltPerMeter = VoltsPerMeter(1)
+
+  implicit class ElectricFieldStrengthConversions[A](n: A)(implicit num: Numeric[A]) {
+    def voltsPerMeter = VoltsPerMeter(n)
+  }
+
+  implicit object ElectricFieldStrengthNumeric extends AbstractQuantityNumeric[ElectricFieldStrength](ElectricFieldStrength.primaryUnit)
+}

shared/src/main/scala/squants/electro/ElectricPotential.scala

@@ -33,7 +33,7 @@ final class ElectricPotential private (val value: Double, val unit: ElectricPote
 
   def /(that: ElectricCurrent): ElectricalResistance = Ohms(this.toVolts / that.toAmperes)
   def /(that: ElectricalResistance): ElectricCurrent = Amperes(this.toVolts / that.toOhms)
-  def /(that: Length) = ??? // returns ElectricFieldStrength
+  def /(that: Length): ElectricFieldStrength = VoltsPerMeter(this.toVolts / that.toMeters)
 
   def toVolts = to(Volts)
   def toMicrovolts = to(Microvolts)

shared/src/main/scala/squants/experimental/unitgroups/ImplicitDimensions.scala

@@ -24,6 +24,7 @@ object ImplicitDimensions {
     implicit val implicitElectricalConductance: Dimension[ElectricalConductance] = ElectricalConductance
     implicit val implicitElectricalResistance: Dimension[ElectricalResistance] = ElectricalResistance
     implicit val implicitElectricCharge: Dimension[ElectricCharge] = ElectricCharge
+    implicit val implicitElectricFieldStrength: Dimension[ElectricFieldStrength] = ElectricFieldStrength
     implicit val implicitElectricPotential: Dimension[ElectricPotential] = ElectricPotential
     implicit val implicitInductance: Dimension[Inductance] = Inductance
     implicit val implicitMagneticFlux: Dimension[MagneticFlux] = MagneticFlux

shared/src/test/scala/squants/electro/ElectricFieldStrengthSpec.scala

@@ -0,0 +1,60 @@
+package squants.electro
+
+import org.scalatest.{FlatSpec, Matchers}
+import squants.QuantityParseException
+import squants.space.Meters
+
+/**
+  * @author Nicolas Vinuesa
+  * @since 1.4
+  *
+  */
+class ElectricFieldStrengthSpec extends FlatSpec with Matchers {
+
+  behavior of "ElectricFieldStrength and its Units of Measure"
+
+  it should "create values using UOM factories" in {
+    VoltsPerMeter(1).toVoltsPerMeter should be(1)
+  }
+
+  it should "create values from properly formatted Strings" in {
+    ElectricFieldStrength("10.22 V/m").get should be(VoltsPerMeter(10.22))
+    ElectricFieldStrength("10.22 zz").failed.get should be(QuantityParseException("Unable to parse ElectricFieldStrength", "10.22 zz"))
+    ElectricFieldStrength("zz V/m").failed.get should be(QuantityParseException("Unable to parse ElectricFieldStrength", "zz V/m"))
+  }
+
+  it should "properly convert to all supported Units of Measure" in {
+    val x = VoltsPerMeter(10)
+    x.toVoltsPerMeter should be(10.0)
+  }
+
+  it should "return properly formatted strings for all supported Units of Measure" in {
+    VoltsPerMeter(1).toString(VoltsPerMeter) should be("1.0 V/m")
+  }
+
+  it should "return Electric Potential when multiplied by Length" in {
+    VoltsPerMeter(1) * Meters(1) should be(Volts(1))
+  }
+
+  behavior of "ElectricFieldStrengthConversions"
+
+  it should "provide aliases for single unit values" in {
+    import ElectricFieldStrengthConversions._
+
+    voltPerMeter should be(VoltsPerMeter(1))
+  }
+
+  it should "provide implicit conversion from Double" in {
+    import ElectricFieldStrengthConversions._
+
+    val d = 10.22
+    d.voltsPerMeter should be(VoltsPerMeter(d))
+  }
+
+  it should "provide Numeric support" in {
+    import ElectricFieldStrengthConversions.ElectricFieldStrengthNumeric
+
+    val rs = List(VoltsPerMeter(100), VoltsPerMeter(10))
+    rs.sum should be(VoltsPerMeter(110))
+  }
+}