Add ElectricDisplacementField with related units.

src/si/electric_displacement_field.rs

@@ -0,0 +1,51 @@
+//! Electric displacement field (base unit coulomb per square meter, m⁻² · A · s).
+
+quantity! {
+    ///Electric displacement field (base unit coulomb per square meter, m⁻² · A · s).
+    quantity: ElectricDisplacementField; "electric displacement field";
+    /// Dimension of electric displacement field, L⁻²TI (base unit coulomb per square meter,
+    /// m⁻² · A · s).
+    dimension: ISQ<
+        N2,     // length
+        Z0,     // mass
+        P1,     // time
+        P1,     // electric current
+        Z0,     // thermodynamic temperature
+        Z0,     // amount of substance
+        Z0>;    // luminous intensity
+    units {
+        @coulomb_per_square_meter: prefix!(none); "C/m²", "coulomb per square meter",
+            "coulombs per square meter";
+        @coulomb_per_square_centimeter: prefix!(none) / prefix!(centi) / prefix!(centi); "C/cm²",
+            "coulomb per square centimeter", "coulombs per square centimeter";
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    storage_types! {
+        use crate::num::One;
+        use crate::si::electric_charge as q;
+        use crate::si::electric_displacement_field as d;
+        use crate::si::quantities::*;
+        use crate::si::area as a;
+        use crate::tests::Test;
+
+        #[test]
+        fn check_dimension() {
+            let _: ElectricDisplacementField<V> = ElectricCharge::new::<q::coulomb>(V::one())
+                / Area::new::<a::square_meter>(V::one());
+        }
+
+        #[test]
+        fn check_units() {
+            test::<q::coulomb, a::square_meter, d::coulomb_per_square_meter>();
+            test::<q::coulomb, a::square_centimeter, d::coulomb_per_square_centimeter>();
+
+            fn test<Q: q::Conversion<V>, A: a::Conversion<V>, D: d::Conversion<V>>() {
+                Test::assert_approx_eq(&ElectricDisplacementField::new::<D>(V::one()),
+                    &(ElectricCharge::new::<Q>(V::one()) / Area::new::<A>(V::one())));
+            }
+        }
+    }
+}

src/si/mod.rs

@@ -62,6 +62,7 @@ system! {
         dynamic_viscosity::DynamicViscosity,
         electric_charge::ElectricCharge,
         electric_current::ElectricCurrent,
+        electric_displacement_field::ElectricDisplacementField,
         electric_permittivity::ElectricPermittivity,
         electric_potential::ElectricPotential,
         electrical_conductance::ElectricalConductance,