[wpiunits] Add resistance units (#7168)

wpiunits/src/main/java/edu/wpi/first/units/ResistanceUnit.java

@@ -0,0 +1,104 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.units;
+
+import edu.wpi.first.units.measure.ImmutableResistance;
+import edu.wpi.first.units.measure.MutResistance;
+import edu.wpi.first.units.measure.Resistance;
+
+/**
+ * Unit of resistance dimension.
+ *
+ * <p>This is the base type for units of resistance dimension. It is also used to specify the
+ * dimension for {@link Measure}: <code>Measure&lt;ResistanceUnit&gt;</code>.
+ *
+ * <p>Actual units (such as {@link Units#Ohms} and {@link Units#KiloOhms}) can be found in the
+ * {@link Units} class.
+ */
+public final class ResistanceUnit extends PerUnit<VoltageUnit, CurrentUnit> {
+  private static final CombinatoryUnitCache<VoltageUnit, CurrentUnit, ResistanceUnit> cache =
+      new CombinatoryUnitCache<>(ResistanceUnit::new);
+
+  ResistanceUnit(VoltageUnit numerator, CurrentUnit denominator) {
+    super(
+        numerator.isBaseUnit() && denominator.isBaseUnit()
+            ? null
+            : combine(numerator.getBaseUnit(), denominator.getBaseUnit()),
+        numerator,
+        denominator);
+  }
+
+  ResistanceUnit(
+      ResistanceUnit baseUnit,
+      UnaryFunction toBaseConverter,
+      UnaryFunction fromBaseConverter,
+      String name,
+      String symbol) {
+    super(baseUnit, toBaseConverter, fromBaseConverter, name, symbol);
+  }
+
+  /**
+   * Combines an voltage and a current unit to form a unit of resistance.
+   *
+   * @param voltage the unit of voltage
+   * @param current the unit of current
+   * @return the combined unit of resistance
+   */
+  public static ResistanceUnit combine(VoltageUnit voltage, CurrentUnit current) {
+    return cache.combine(voltage, current);
+  }
+
+  @Override
+  public ResistanceUnit getBaseUnit() {
+    return (ResistanceUnit) super.getBaseUnit();
+  }
+
+  @Override
+  public Resistance of(double magnitude) {
+    return new ImmutableResistance(magnitude, toBaseUnits(magnitude), this);
+  }
+
+  @Override
+  public Resistance ofBaseUnits(double baseUnitMagnitude) {
+    return new ImmutableResistance(fromBaseUnits(baseUnitMagnitude), baseUnitMagnitude, this);
+  }
+
+  @Override
+  public Resistance zero() {
+    return (Resistance) super.zero();
+  }
+
+  @Override
+  public Resistance one() {
+    return (Resistance) super.one();
+  }
+
+  @Override
+  public MutResistance mutable(double initialMagnitude) {
+    return new MutResistance(initialMagnitude, toBaseUnits(initialMagnitude), this);
+  }
+
+  /**
+   * Creates a ratio unit between this unit and an arbitrary other unit.
+   *
+   * @param other the other unit
+   * @param <U> the type of the other unit
+   * @return the ratio unit
+   */
+  public <U extends Unit> PerUnit<ResistanceUnit, U> per(U other) {
+    return PerUnit.combine(this, other);
+  }
+
+  /**
+   * Converts a measurement value in terms of another power unit to this unit.
+   *
+   * @param magnitude the magnitude of the measurement in terms of the other power unit
+   * @param otherUnit the other power unit
+   * @return the value of the measurement in terms of this unit
+   */
+  public double convertFrom(double magnitude, ResistanceUnit otherUnit) {
+    return fromBaseUnits(otherUnit.toBaseUnits(magnitude));
+  }
+}