1 files changed, 47 insertions, 1 deletions
diff --git a/src/org/unitConverter/unit/BaseUnit.java b/src/org/unitConverter/unit/BaseUnit.java
index 1f0c825..894d338 100755
--- a/src/org/unitConverter/unit/BaseUnit.java
+++ b/src/org/unitConverter/unit/BaseUnit.java
@@ -28,7 +28,7 @@ import org.unitConverter.dimension.UnitDimension;
  * @since 2018-12-23
  * @since v0.1.0
  */
-public final class BaseUnit extends AbstractUnit {
+public final class BaseUnit extends AbstractUnit implements OperatableUnit {
 	/**
 	 * Is this unit a full base (i.e. m, s, ... but not N, J, ...)
 	 * 
@@ -126,6 +126,35 @@ public final class BaseUnit extends AbstractUnit {
 		return result;
 	}
 
+	@Override
+	public LinearUnit negated() {
+		return this.times(-1);
+	}
+
+	@Override
+	public OperatableUnit plus(final OperatableUnit addend) {
+		Objects.requireNonNull(addend, "addend must not be null.");
+
+		// reject addends that cannot be added to this unit
+		if (!this.getSystem().equals(addend.getSystem()))
+			throw new IllegalArgumentException(
+					String.format("Incompatible units for addition or subtraction \"%s\" and \"%s\".", this, addend));
+		if (!this.getDimension().equals(addend.getDimension()))
+			throw new IllegalArgumentException(
+					String.format("Incompatible units for addition or subtraction \"%s\" and \"%s\".", this, addend));
+
+		// add them together
+		if (addend instanceof BaseUnit)
+			return this.times(2);
+		else
+			return addend.plus(this);
+	}
+
+	@Override
+	public BaseUnit reciprocal() {
+		return this.toExponent(-1);
+	}
+
 	/**
 	 * Multiplies this unit by another unit.
 	 * 
@@ -159,6 +188,22 @@ public final class BaseUnit extends AbstractUnit {
 		return new LinearUnit(this, multiplier);
 	}
 
+	@Override
+	public OperatableUnit times(final OperatableUnit multiplier) {
+		Objects.requireNonNull(multiplier, "multiplier must not be null.");
+
+		// reject multipliers that cannot be muliplied by this unit
+		if (!this.getSystem().equals(multiplier.getSystem()))
+			throw new IllegalArgumentException(String
+					.format("Incompatible units for multiplication or division \"%s\" and \"%s\".", this, multiplier));
+
+		// multiply the units
+		if (multiplier instanceof BaseUnit)
+			return new BaseUnit(this.getDimension().times(multiplier.getDimension()), this.getSystem());
+		else
+			return multiplier.times(this);
+	}
+
 	/**
 	 * Returns this unit, but to an exponent.
 	 * 
@@ -168,6 +213,7 @@ public final class BaseUnit extends AbstractUnit {
 	 * @since 2019-01-15
 	 * @since v0.1.0
 	 */
+	@Override
 	public BaseUnit toExponent(final int exponent) {
 		return this.getSystem().getBaseUnit(this.getDimension().toExponent(exponent));
 	}