Add "inch of mercury" pressure unit as US Custom Unit

Signed-off-by: Tobias Lorenz <tobias.lorenz@gmx.net>

docs/reference/systems/isq/si/uscs/pressure.rst

@@ -0,0 +1,4 @@
+Pressure
+========
+
+.. doxygenfile:: si/uscs/pressure.h

docs/reference/systems/isq/si_uscs.rst

@@ -5,3 +5,4 @@ U.S. Customary Units (based on SI)
     :maxdepth: 2
 
     si/uscs/length
+    si/uscs/pressure

src/systems/si-uscs/CMakeLists.txt

@@ -23,5 +23,6 @@
 cmake_minimum_required(VERSION 3.19)
 
 add_units_module(
-    si-uscs DEPENDENCIES mp-units::si HEADERS include/units/isq/si/uscs/length.h include/units/isq/si/uscs/uscs.h
+    si-uscs DEPENDENCIES mp-units::si HEADERS include/units/isq/si/uscs/length.h include/units/isq/si/uscs/pressure.h
+                                              include/units/isq/si/uscs/uscs.h
 )

src/systems/si-uscs/include/units/isq/si/uscs/pressure.h

@@ -0,0 +1,88 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+// Copyright (c) 2023 Tobias Lorenz
+//
+// 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, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+// IWYU pragma: begin_exports
+#include <units/isq/dimensions/pressure.h>
+#include <units/quantity.h>
+#include <units/reference.h>
+#include <units/symbol_text.h>
+// IWYU pragma: end_exports
+
+#include <units/isq/si/pressure.h>
+#include <units/unit.h>
+
+namespace units::isq::si::uscs {
+
+// https://en.wikipedia.org/wiki/Inch_of_mercury
+// https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8
+struct inch_of_mercury : named_scaled_unit<inch_of_mercury, "inHg", mag<ratio(3'386'389, 1'000)>(), si::pascal> {};
+
+#ifndef UNITS_NO_LITERALS
+
+inline namespace literals {
+
+// inHg
+constexpr auto operator"" _q_inHg(unsigned long long l)
+{
+  gsl_ExpectsAudit(std::in_range<std::int64_t>(l));
+  return si::pressure<units::isq::si::uscs::inch_of_mercury, std::int64_t>(static_cast<std::int64_t>(l));
+}
+constexpr auto operator"" _q_inHg(long double l)
+{
+  return si::pressure<units::isq::si::uscs::inch_of_mercury, long double>(l);
+}
+
+}  // namespace literals
+
+#endif  // UNITS_NO_LITERALS
+
+#ifndef UNITS_NO_REFERENCES
+
+namespace pressure_references {
+
+inline constexpr auto inHg = reference<si::dim_pressure, uscs::inch_of_mercury>{};
+
+}  // namespace pressure_references
+
+namespace references {
+
+using namespace pressure_references;
+
+}  // namespace references
+
+#endif  // UNITS_NO_REFERENCES
+
+}  // namespace units::isq::si::uscs
+
+#ifndef UNITS_NO_ALIASES
+
+namespace units::aliases::isq::si::uscs::inline pressure {
+
+template<Representation Rep = double>
+using inHg = units::isq::si::pressure<units::isq::si::uscs::inch_of_mercury, Rep>;
+
+}  // namespace units::aliases::isq::si::uscs::inline pressure
+
+#endif  // UNITS_NO_ALIASES

src/systems/si-uscs/include/units/isq/si/uscs/uscs.h

@@ -24,4 +24,5 @@
 
 // IWYU pragma: begin_exports
 #include <units/isq/si/uscs/length.h>
+#include <units/isq/si/uscs/pressure.h>
 // IWYU pragma: end_exports

test/unit_test/static/us_test.cpp

@@ -23,7 +23,9 @@
 #include <units/isq/si/international/length.h>
 #include <units/isq/si/international/speed.h>
 #include <units/isq/si/length.h>
+#include <units/isq/si/pressure.h>
 #include <units/isq/si/time.h>
+#include <units/isq/si/uscs/pressure.h>
 #include <units/unit.h>
 
 namespace {
@@ -31,6 +33,7 @@ namespace {
 using namespace units;
 using namespace units::isq::si;
 using namespace units::isq::si::international;
+using namespace units::isq::si::uscs;
 
 /* ************** BASE DIMENSIONS **************** */
 
@@ -52,4 +55,12 @@ static_assert(10.0_q_mi / 2_q_h == 5_q_mi_per_h);
 
 static_assert(mile_per_hour::symbol == "mi/h");
 
+
+/* ************** US CUSTOMARY UNITS **************** */
+
+// pressure
+
+// 29.9213 inHg = 1013.25 hPa
+static_assert(1_q_inHg == 3386.389_q_Pa);
+
 }  // namespace