From 94f1b8ce996cc05227bbc694ccc4895601e3682b Mon Sep 17 00:00:00 2001
From: Vlad Voronenkov <v.v.voronenkov@ya.ru>
Date: Tue, 2 Aug 2022 19:01:55 +0200
Subject: [PATCH] Add diffusion coefficient quantities and related units.

Resolves #321

Co-authored-by: Mike Boutin <mike.boutin@gmail.com>
---
 src/si/diffusion_coefficient.rs | 66 +++++++++++++++++++++++++++++++++
 src/si/mod.rs                   |  1 +
 2 files changed, 67 insertions(+)
 create mode 100644 src/si/diffusion_coefficient.rs

diff --git a/src/si/diffusion_coefficient.rs b/src/si/diffusion_coefficient.rs
new file mode 100644
index 00000000..959d4ac0
--- /dev/null
+++ b/src/si/diffusion_coefficient.rs
@@ -0,0 +1,66 @@
+//! Diffusion coefficient (base unit square meter per second, m² · s⁻¹).
+
+quantity! {
+    /// Diffusion coefficient (base unit square meter per second, m² · s⁻¹).
+    quantity: DiffusionCoefficient; "diffusion coefficient";
+    /// Dimension of diffusion coefficient, L²T⁻¹ (base unit square meter per second, m² · s⁻¹).
+    dimension: ISQ<
+        P2,     // length
+        Z0,     // mass
+        N1,     // time
+        Z0,     // electric current
+        Z0,     // thermodynamic temperature
+        Z0,     // amount of substance
+        Z0>;    // luminous intensity
+    units {
+        @square_meter_per_second: prefix!(none); "m²/s", "square meter per second",
+            "square meters per second";
+        @square_centimeter_per_second: prefix!(centi) * prefix!(centi); "cm²/s",
+            "square centimeter per second", "square centimeters per second";
+        @square_millimeter_per_second: prefix!(milli) * prefix!(milli); "mm²/s",
+            "square millimeter per second", "square millimeters per second";
+        @square_micrometer_per_second: prefix!(micro) * prefix!(micro); "µm²/s",
+            "square micrometer per second", "square micrometers per second";
+        @square_nanometer_per_second: prefix!(nano) * prefix!(nano); "nm²/s",
+            "square nanometer per second", "square nanometers per second";
+        @stokes: prefix!(centi) * prefix!(centi); "St", "Stokes", "Stokes";
+        @centistokes: prefix!(centi) * prefix!(centi) * prefix!(centi); "cSt", "centistokes",
+            "centistokes";
+        }
+}
+
+#[cfg(test)]
+mod test {
+    storage_types! {
+        use crate::num::One;
+        use crate::si::quantities::*;
+        use crate::si::time as t;
+        use crate::si::area as area;
+        use crate::si::diffusion_coefficient as dc;
+
+        use crate::tests::Test;
+
+        #[test]
+        fn check_dimension() {
+            let _: DiffusionCoefficient<V> = Area::new::<area::square_meter>(V::one())
+                / Time::new::<t::second>(V::one());
+        }
+
+        #[test]
+        fn check_units() {
+            test::<area::square_meter, t::second, dc::square_meter_per_second>();
+            test::<area::square_centimeter, t::second, dc::square_centimeter_per_second>();
+            test::<area::square_millimeter, t::second, dc::square_millimeter_per_second>();
+            test::<area::square_micrometer, t::second, dc::square_micrometer_per_second>();
+            test::<area::square_nanometer, t::second, dc::square_nanometer_per_second>();
+            test::<area::square_centimeter, t::second, dc::stokes>();
+            test::<area::square_millimeter, t::second, dc::centistokes>();
+
+            fn test<A: area::Conversion<V>, T: t::Conversion<V>, DC: dc::Conversion<V>>() {
+                Test::assert_approx_eq(&DiffusionCoefficient::new::<DC>(V::one()),
+                    &(Area::new::<A>(V::one())
+                        / Time::new::<T>(V::one())));
+            }
+        }
+    }
+}
diff --git a/src/si/mod.rs b/src/si/mod.rs
index 5a986a4c..175cddf6 100644
--- a/src/si/mod.rs
+++ b/src/si/mod.rs
@@ -58,6 +58,7 @@ system! {
         catalytic_activity::CatalyticActivity,
         catalytic_activity_concentration::CatalyticActivityConcentration,
         curvature::Curvature,
+        diffusion_coefficient::DiffusionCoefficient,
         electric_charge::ElectricCharge,
         electric_current::ElectricCurrent,
         electric_potential::ElectricPotential,