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diff --git a/src/org/unitConverter/unit/FunctionalUnit.java b/src/org/unitConverter/unit/FunctionalUnit.java
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+++ b/src/org/unitConverter/unit/FunctionalUnit.java
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+/**
+ * Copyright (C) 2019 Adrien Hopkins
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.unitConverter.unit;
+
+import java.util.function.DoubleUnaryOperator;
+
+/**
+ * A unit that uses functional objects to convert to and from its base.
+ * 
+ * @author Adrien Hopkins
+ * @since 2019-05-22
+ */
+final class FunctionalUnit extends AbstractUnit {
+	/**
+	 * Returns a unit from its base and the functions it uses to convert to and from its base.
+	 * 
+	 * @param base
+	 *            unit's base
+	 * @param converterFrom
+	 *            function that accepts a value expressed in the unit's base and returns that value expressed in this
+	 *            unit.
+	 * @param converterTo
+	 *            function that accepts a value expressed in the unit and returns that value expressed in the unit's
+	 *            base.
+	 * @return a unit that uses the provided functions to convert.
+	 * @since 2019-05-22
+	 */
+	public static FunctionalUnit valueOf(final BaseUnit base, final DoubleUnaryOperator converterFrom,
+			final DoubleUnaryOperator converterTo) {
+		return new FunctionalUnit(base, converterFrom, converterTo);
+	}
+
+	/**
+	 * A function that accepts a value expressed in the unit's base and returns that value expressed in this unit.
+	 * 
+	 * @since 2019-05-22
+	 */
+	private final DoubleUnaryOperator converterFrom;
+
+	/**
+	 * A function that accepts a value expressed in the unit and returns that value expressed in the unit's base.
+	 * 
+	 * @since 2019-05-22
+	 */
+	private final DoubleUnaryOperator converterTo;
+
+	/**
+	 * Creates the {@code FunctionalUnit}.
+	 * 
+	 * @param base
+	 *            unit's base
+	 * @param converterFrom
+	 *            function that accepts a value expressed in the unit's base and returns that value expressed in this
+	 *            unit.
+	 * @param converterTo
+	 *            function that accepts a value expressed in the unit and returns that value expressed in the unit's
+	 *            base.
+	 * @since 2019-05-22
+	 */
+	private FunctionalUnit(final BaseUnit base, final DoubleUnaryOperator converterFrom,
+			final DoubleUnaryOperator converterTo) {
+		super(base);
+		this.converterFrom = converterFrom;
+		this.converterTo = converterTo;
+	}
+
+	@Override
+	public double convertFromBase(final double value) {
+		return this.converterFrom.applyAsDouble(value);
+	}
+
+	@Override
+	public double convertToBase(final double value) {
+		return this.converterTo.applyAsDouble(value);
+	}
+
+}