Added unit prefixes.

3 files changed, 229 insertions, 1 deletions

diff --git a/src/org/unitConverter/math/DecimalComparison.java b/src/org/unitConverter/math/DecimalComparison.java
index 7cdbe5b..859e8da 100644
--- a/src/org/unitConverter/math/DecimalComparison.java
+++ b/src/org/unitConverter/math/DecimalComparison.java
@@ -16,6 +16,8 @@
  */
 package org.unitConverter.math;
 
+import java.math.BigDecimal;
+
 /**
  * A class that contains methods to compare float and double values.
  * 
@@ -44,6 +46,18 @@ public final class DecimalComparison {
 
 	/**
 	 * Tests for equality of double values using {@link #DOUBLE_EPSILON}.
+	 * <p>
+	 * <strong>WARNING: </strong>this method is not technically transitive. If a and b are off by slightly less than
+	 * {@code epsilon * max(abs(a), abs(b))}, and b and c are off by slightly less than
+	 * {@code epsilon * max(abs(b), abs(c))}, then equals(a, b) and equals(b, c) will both return true, but equals(a, c)
+	 * will return false. However, this situation is very unlikely to ever happen in a real programming situation.
+	 * <p>
+	 * If this does become a concern, some ways to solve this problem:
+	 * <ol>
+	 * <li>Raise the value of epsilon using {@link #equals(double, double, double)} (this does not make a violation of
+	 * transitivity impossible, it just significantly reduces the chances of it happening)
+	 * <li>Use {@link BigDecimal} instead of {@code double} (this will make a violation of transitivity 100% impossible)
+	 * </ol>
 	 * 
 	 * @param a
 	 *            first value to test
@@ -52,6 +66,7 @@ public final class DecimalComparison {
 	 * @return whether they are equal
 	 * @since 2019-03-18
 	 * @since v0.2.0
+	 * @see #hashCode(double)
 	 */
 	public static final boolean equals(final double a, final double b) {
 		return DecimalComparison.equals(a, b, DOUBLE_EPSILON);
@@ -60,6 +75,19 @@ public final class DecimalComparison {
 	/**
 	 * Tests for double equality using a custom epsilon value.
 	 * 
+	 * <p>
+	 * <strong>WARNING: </strong>this method is not technically transitive. If a and b are off by slightly less than
+	 * {@code epsilon * max(abs(a), abs(b))}, and b and c are off by slightly less than
+	 * {@code epsilon * max(abs(b), abs(c))}, then equals(a, b) and equals(b, c) will both return true, but equals(a, c)
+	 * will return false. However, this situation is very unlikely to ever happen in a real programming situation.
+	 * <p>
+	 * If this does become a concern, some ways to solve this problem:
+	 * <ol>
+	 * <li>Raise the value of epsilon (this does not make a violation of transitivity impossible, it just significantly
+	 * reduces the chances of it happening)
+	 * <li>Use {@link BigDecimal} instead of {@code double} (this will make a violation of transitivity 100% impossible)
+	 * </ol>
+	 * 
 	 * @param a
 	 *            first value to test
 	 * @param b
@@ -77,6 +105,19 @@ public final class DecimalComparison {
 	/**
 	 * Tests for equality of float values using {@link #FLOAT_EPSILON}.
 	 * 
+	 * <p>
+	 * <strong>WARNING: </strong>this method is not technically transitive. If a and b are off by slightly less than
+	 * {@code epsilon * max(abs(a), abs(b))}, and b and c are off by slightly less than
+	 * {@code epsilon * max(abs(b), abs(c))}, then equals(a, b) and equals(b, c) will both return true, but equals(a, c)
+	 * will return false. However, this situation is very unlikely to ever happen in a real programming situation.
+	 * <p>
+	 * If this does become a concern, some ways to solve this problem:
+	 * <ol>
+	 * <li>Raise the value of epsilon using {@link #equals(float, float, float)} (this does not make a violation of
+	 * transitivity impossible, it just significantly reduces the chances of it happening)
+	 * <li>Use {@link BigDecimal} instead of {@code float} (this will make a violation of transitivity 100% impossible)
+	 * </ol>
+	 * 
 	 * @param a
 	 *            first value to test
 	 * @param b
@@ -92,6 +133,19 @@ public final class DecimalComparison {
 	/**
 	 * Tests for float equality using a custom epsilon value.
 	 * 
+	 * <p>
+	 * <strong>WARNING: </strong>this method is not technically transitive. If a and b are off by slightly less than
+	 * {@code epsilon * max(abs(a), abs(b))}, and b and c are off by slightly less than
+	 * {@code epsilon * max(abs(b), abs(c))}, then equals(a, b) and equals(b, c) will both return true, but equals(a, c)
+	 * will return false. However, this situation is very unlikely to ever happen in a real programming situation.
+	 * <p>
+	 * If this does become a concern, some ways to solve this problem:
+	 * <ol>
+	 * <li>Raise the value of epsilon (this does not make a violation of transitivity impossible, it just significantly
+	 * reduces the chances of it happening)
+	 * <li>Use {@link BigDecimal} instead of {@code float} (this will make a violation of transitivity 100% impossible)
+	 * </ol>
+	 * 
 	 * @param a
 	 *            first value to test
 	 * @param b
@@ -106,6 +160,19 @@ public final class DecimalComparison {
 		return Math.abs(a - b) <= epsilon * Math.max(Math.abs(a), Math.abs(b));
 	}
 
+	/**
+	 * Takes the hash code of doubles. Values that are equal according to {@link #equals(double, double)} will have the
+	 * same hash code.
+	 * 
+	 * @param d
+	 *            double to hash
+	 * @return hash code of double
+	 * @since 2019-10-16
+	 */
+	public static final int hash(final double d) {
+		return Float.hashCode((float) d);
+	}
+
 	// You may NOT get any DecimalComparison instances
 	private DecimalComparison() {
 		throw new AssertionError();
diff --git a/src/org/unitConverter/newUnits/LinearUnit.java b/src/org/unitConverter/newUnits/LinearUnit.java
index 5a589b7..7600dad 100644
--- a/src/org/unitConverter/newUnits/LinearUnit.java
+++ b/src/org/unitConverter/newUnits/LinearUnit.java
@@ -29,6 +29,21 @@ import org.unitConverter.math.ObjectProduct;
  */
 public final class LinearUnit extends AbstractUnit {
 	/**
+	 * Gets a {@code LinearUnit} from a unit and a value. For example, converts '59 °F' to a linear unit with the value
+	 * of '288.15 K'
+	 * 
+	 * @param unit
+	 *            unit to convert
+	 * @param value
+	 *            value to convert
+	 * @return value expressed as a {@code LinearUnit}
+	 * @since 2019-10-16
+	 */
+	public static LinearUnit fromValue(final Unit unit, final double value) {
+		return new LinearUnit(unit.getBase(), unit.convertToBase(value));
+	}
+
+	/**
 	 * Gets a {@code LinearUnit} from a unit base and a conversion factor. In other words, gets the product of
 	 * {@code unitBase} and {@code conversionFactor}, expressed as a {@code LinearUnit}.
 	 * 
@@ -129,7 +144,7 @@ public final class LinearUnit extends AbstractUnit {
 
 	@Override
 	public int hashCode() {
-		return Objects.hash(this.getBase(), this.getConversionFactor());
+		return 31 * this.getBase().hashCode() + DecimalComparison.hash(this.getConversionFactor());
 	}
 
 	/**
@@ -258,4 +273,16 @@ public final class LinearUnit extends AbstractUnit {
 		return Double.toString(this.conversionFactor) + " * " + this.getBase().toString(BaseUnit::getSymbol);
 	}
 
+	/**
+	 * Returns the result of applying {@code prefix} to this unit.
+	 * 
+	 * @param prefix
+	 *            prefix to apply
+	 * @return unit with prefix
+	 * @since 2019-03-18
+	 * @since v0.2.0
+	 */
+	public LinearUnit withPrefix(final UnitPrefix prefix) {
+		return this.times(prefix.getMultiplier());
+	}
 }
diff --git a/src/org/unitConverter/newUnits/UnitPrefix.java b/src/org/unitConverter/newUnits/UnitPrefix.java
new file mode 100644
index 0000000..905ca19
--- /dev/null
+++ b/src/org/unitConverter/newUnits/UnitPrefix.java
@@ -0,0 +1,134 @@
+/**
+ * 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.newUnits;
+
+import org.unitConverter.math.DecimalComparison;
+
+/**
+ * A prefix that can be applied to a {@code LinearUnit} to multiply it by some value
+ * 
+ * @author Adrien Hopkins
+ * @since 2019-10-16
+ */
+public final class UnitPrefix {
+	/**
+	 * The number that this prefix multiplies units by
+	 * 
+	 * @since 2019-10-16
+	 */
+	private final double multiplier;
+
+	/**
+	 * Creates the {@code DefaultUnitPrefix}.
+	 * 
+	 * @param multiplier
+	 * @since 2019-01-14
+	 * @since v0.2.0
+	 */
+	private UnitPrefix(final double multiplier) {
+		this.multiplier = multiplier;
+	}
+
+	/**
+	 * Divides this prefix by a scalar
+	 * 
+	 * @param divisor
+	 *            number to divide by
+	 * @return quotient of prefix and scalar
+	 * @since 2019-10-16
+	 */
+	public UnitPrefix dividedBy(final double divisor) {
+		return new UnitPrefix(this.getMultiplier() / divisor);
+	}
+
+	/**
+	 * Divides this prefix by {@code other}.
+	 * 
+	 * @param other
+	 *            prefix to divide by
+	 * @return quotient of prefixes
+	 * @since 2019-04-13
+	 * @since v0.2.0
+	 */
+	public UnitPrefix dividedBy(final UnitPrefix other) {
+		return new UnitPrefix(this.getMultiplier() / other.getMultiplier());
+	}
+
+	@Override
+	public boolean equals(final Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (!(obj instanceof UnitPrefix))
+			return false;
+		final UnitPrefix other = (UnitPrefix) obj;
+		return DecimalComparison.equals(this.getMultiplier(), other.getMultiplier());
+	}
+
+	public double getMultiplier() {
+		return this.multiplier;
+	}
+
+	@Override
+	public int hashCode() {
+		return DecimalComparison.hash(this.getMultiplier());
+	}
+
+	/**
+	 * Multiplies this prefix by a scalar
+	 * 
+	 * @param multiplicand
+	 *            number to multiply by
+	 * @return product of prefix and scalar
+	 * @since 2019-10-16
+	 */
+	public UnitPrefix times(final double multiplicand) {
+		return new UnitPrefix(this.getMultiplier() * multiplicand);
+	}
+
+	/**
+	 * Multiplies this prefix by {@code other}.
+	 * 
+	 * @param other
+	 *            prefix to multiply by
+	 * @return product of prefixes
+	 * @since 2019-04-13
+	 * @since v0.2.0
+	 */
+	public UnitPrefix times(final UnitPrefix other) {
+		return new UnitPrefix(this.getMultiplier() * other.getMultiplier());
+	}
+
+	/**
+	 * Raises this prefix to an exponent.
+	 * 
+	 * @param exponent
+	 *            exponent to raise to
+	 * @return result of exponentiation.
+	 * @since 2019-04-13
+	 * @since v0.2.0
+	 */
+	public UnitPrefix toExponent(final double exponent) {
+		return new UnitPrefix(Math.pow(this.getMultiplier(), exponent));
+	}
+
+	@Override
+	public String toString() {
+		return String.format("Unit prefix equal to %s", this.multiplier);
+	}
+}