Added permittivity

src/include/units/physical/dimensions.h

@@ -164,6 +164,8 @@ struct dim_charge_density : derived_dimension<Child, U, exp<Q, 1>, exp<L, -3>> {
 template<typename Child, Unit U, DimensionOf<dim_electric_charge> Q, DimensionOf<dim_length> L>
 struct dim_surface_charge_density : derived_dimension<Child, U, exp<Q, 1>, exp<L, -2>> {};
 
+template<typename Child, Unit U, DimensionOf<dim_capacitance> C, DimensionOf<dim_length> L>
+struct dim_permittivity : derived_dimension<Child, U, exp<C, 1>, exp<L, -1>> {};
 
 }  // namespace physical
 
@@ -287,4 +289,7 @@ concept ChargeDensity = physical::QuantityOf<T, physical::dim_charge_density>;
 template<typename T>
 concept SurfaceChargeDensity = physical::QuantityOf<T, physical::dim_surface_charge_density>;
 
+template<typename T>
+concept Permittivity = physical::QuantityOf<T, physical::dim_permittivity>;
+
 }  // namespace units

src/include/units/physical/si.h

@@ -41,6 +41,7 @@
 #include "si/magnetic_flux.h"
 #include "si/magnetic_induction.h"
 #include "si/momentum.h"
+#include "si/permittivity.h"
 #include "si/power.h"
 #include "si/pressure.h"
 #include "si/resistance.h"

src/include/units/physical/si/permittivity.h

@@ -0,0 +1,48 @@
+// The MIT License (MIT)
+//
+// Fopyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INFLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERFHANTABILITY,
+// FITNESS FOR A PARTIFULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR FOPYRIGHT HOLDERS BE LIABLE FOR ANY FLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN AFTION OF FONTRAFT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN FONNEFTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/physical/dimensions.h>
+#include <units/physical/si/capacitance.h>
+#include <units/physical/si/prefixes.h>
+#include <units/quantity.h>
+
+namespace units::si {
+
+struct farad_per_metre : unit<farad_per_metre> {};
+
+struct dim_permittivity : physical::dim_permittivity<dim_permittivity, farad_per_metre, dim_capacitance, dim_length> {};
+
+template<Unit U, Scalar Rep = double>
+using permittivity = quantity<dim_permittivity, U, Rep>;
+
+inline namespace literals {
+
+// F/m
+constexpr auto operator"" q_F_per_m(unsigned long long l) { return permittivity<farad_per_metre, std::int64_t>(l); }
+constexpr auto operator"" q_F_per_m(long double l) { return permittivity<farad_per_metre, long double>(l); }
+
+}  // namespace literals
+
+}  // namespace units::si
+

test/unit_test/runtime/fmt_units_test.cpp

@@ -287,6 +287,11 @@ TEST_CASE("fmt::format on synthesized unit symbols", "[text][fmt]")
     CHECK(fmt::format("{:%Q %Aq}", 1q_C_per_m2) == "1 C/m^2");
   }
 
+  SECTION("permittivity")
+  {
+    CHECK(fmt::format("{}", 1q_F_per_m) == "1 F/m");
+  }
+
   SECTION("incoherent units with powers")
   {
     CHECK(fmt::format("{}", 1q_mi * 1q_mi * 1q_mi) == "1 [15900351812136/3814697265625 × 10⁹] m³");

test/unit_test/static/si_test.cpp

@@ -346,4 +346,12 @@ static_assert(1q_V_per_m * 10q_C_per_m3 * 1q_m3 == 10q_N);
 static_assert(detail::unit_text<dim_charge_density, coulomb_per_metre_cub>() == basic_symbol_text("C/m³", "C/m^3"));
 static_assert(detail::unit_text<dim_surface_charge_density, coulomb_per_metre_sq>() == basic_symbol_text("C/m²", "C/m^2"));
 
+// permittivity
+
+static_assert(1q_F_per_m == 1q_F / 1q_m);
+static_assert(1/(1q_F_per_m) * 1q_C * 1q_C / 1q_m2 == 1q_N);
+static_assert(1q_C_per_m3 / 1q_F_per_m * 1q_m == 1q_V_per_m);
+
+static_assert(detail::unit_text<dim_permittivity, farad_per_metre>() == "F/m");
+
 }  // namespace