Add electric potential quantity and units.

Resolves #74.

src/si/electric_potential.rs

@@ -0,0 +1,96 @@
+//! Electric potential (base unit volt, m<sup>2</sup> · kg · s<sup>-3</sup> · A<sup>-1</sup>).
+
+quantity! {
+    /// Electric potential (base unit volt, m<sup>2</sup> · kg · s<sup>-3</sup> · A<sup>-1</sup>).
+    quantity: ElectricPotential; "electric potential";
+    /// Electric potential dimension, m<sup>2</sup> · kg · s<sup>-3</sup> · A<sup>-1</sup>.
+    dimension: ISQ<
+        P2,     // length
+        P1,     // mass
+        N3,     // time
+        N1,     // electric current
+        Z0,     // thermodynamic temperature
+        Z0,     // amount of substance
+        Z0>;    // luminous intensity
+    units {
+        @yottavolt: prefix!(yotta); "YV", "yottavolt", "yottavolts";
+        @zettavolt: prefix!(zetta); "ZV", "zettavolt", "zettavolts";
+        @exavolt: prefix!(exa); "EV", "exavolt", "exavolts";
+        @petavolt: prefix!(peta); "PV", "petavolt", "petavolts";
+        @teravolt: prefix!(tera); "TV", "teravolt", "teravolts";
+        @gigavolt: prefix!(giga); "GV", "gigavolt", "gigavolts";
+        @megavolt: prefix!(mega); "MV", "megavolt", "megavolts";
+        @kilovolt: prefix!(kilo); "kV", "kilovolt", "kilovolts";
+        @hectovolt: prefix!(hecto); "hV", "hectovolt", "hectovolts";
+        @decavolt: prefix!(deca); "daV", "decavolt", "decavolts";
+        /// Derived unit of electric potential.
+        @volt: prefix!(none); "V", "volt", "volts";
+        @decivolt: prefix!(deci); "dV", "decivolt", "decivolts";
+        @centivolt: prefix!(centi); "cV", "centivolt", "centivolts";
+        @millivolt: prefix!(milli); "mV", "millivolt", "millivolts";
+        @microvolt: prefix!(micro); "µV", "microvolt", "microvolts";
+        @nanovolt: prefix!(nano); "nV", "nanovolt", "nanovolts";
+        @picovolt: prefix!(pico); "pV", "picovolt", "picovolts";
+        @femtovolt: prefix!(femto); "fV", "femtovolt", "femtovolts";
+        @attovolt: prefix!(atto); "aV", "attovolt", "attovolts";
+        @zeptovolt: prefix!(zepto); "zV", "zeptovolt", "zeptovolts";
+        @yoctovolt: prefix!(yocto); "yV", "yoctovolt", "yoctovolts";
+
+        @abvolt: 1.0_E-8; "abV", "abvolt", "abvolts";
+        @statvolt: 2.997_925_E2; "statV", "statvolt", "statvolts";
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    storage_types! {
+        use num::One;
+        use si::quantities::*;
+        use si::mass as m;
+        use si::time as t;
+        use si::area as a;
+        use si::electric_current as i;
+        use si::electric_potential as v;
+        use tests::Test;
+
+        #[test]
+        fn check_dimension() {
+            let _: ElectricPotential<V> = Area::new::<a::square_meter>(V::one())
+                * Mass::new::<m::kilogram>(V::one())
+                / (ElectricCurrent::new::<i::ampere>(V::one())
+                    * Time::new::<t::second>(V::one()).powi(::typenum::P3::new()));
+        }
+
+        #[test]
+        fn check_units() {
+            test::<i::yottaampere, v::yoctovolt>();
+            test::<i::zettaampere, v::zeptovolt>();
+            test::<i::exaampere, v::attovolt>();
+            test::<i::petaampere, v::femtovolt>();
+            test::<i::teraampere, v::picovolt>();
+            test::<i::gigaampere, v::nanovolt>();
+            test::<i::megaampere, v::microvolt>();
+            test::<i::kiloampere, v::millivolt>();
+            test::<i::hectoampere, v::centivolt>();
+            test::<i::decaampere, v::decivolt>();
+            test::<i::ampere, v::volt>();
+            test::<i::deciampere, v::decavolt>();
+            test::<i::centiampere, v::hectovolt>();
+            test::<i::milliampere, v::kilovolt>();
+            test::<i::microampere, v::megavolt>();
+            test::<i::nanoampere, v::gigavolt>();
+            test::<i::picoampere, v::teravolt>();
+            test::<i::femtoampere, v::petavolt>();
+            test::<i::attoampere, v::exavolt>();
+            test::<i::zeptoampere, v::zettavolt>();
+            test::<i::yoctoampere, v::yottavolt>();
+
+            fn test<I: i::Conversion<V>, E: v::Conversion<V>>() {
+                Test::assert_approx_eq(&ElectricPotential::new::<E>(V::one()),
+                    &(Area::new::<a::square_meter>(V::one()) * Mass::new::<m::kilogram>(V::one())
+                        / (ElectricCurrent::new::<I>(V::one())
+                            * Time::new::<t::second>(V::one()).powi(::typenum::P3::new()))));
+            }
+        }
+    }
+}

src/si/mod.rs

@@ -26,6 +26,7 @@ system! {
         available_energy::AvailableEnergy,
         area::Area,
         electric_current::ElectricCurrent,
+        electric_potential::ElectricPotential,
         energy::Energy,
         force::Force,
         frequency::Frequency,