5 files changed, 1139 insertions, 11 deletions

diff --git a/src/main/java/sevenUnits/utils/NameSymbol.java b/src/main/java/sevenUnits/utils/NameSymbol.java
new file mode 100644
index 0000000..7ef2967
--- /dev/null
+++ b/src/main/java/sevenUnits/utils/NameSymbol.java
@@ -0,0 +1,308 @@
+/**
+ * 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 sevenUnits.utils;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+
+/**
+ * A class that can be used to specify names and a symbol for a unit.
+ * 
+ * @author Adrien Hopkins
+ * @since 2019-10-21
+ */
+public final class NameSymbol {
+	public static final NameSymbol EMPTY = new NameSymbol(Optional.empty(),
+			Optional.empty(), new HashSet<>());
+	
+	/**
+	 * Creates a {@code NameSymbol}, ensuring that if primaryName is null and
+	 * otherNames is not empty, one name is moved from otherNames to primaryName
+	 * 
+	 * Ensure that otherNames is not a copy of the inputted argument.
+	 */
+	private static final NameSymbol create(final String name,
+			final String symbol, final Set<String> otherNames) {
+		final Optional<String> primaryName;
+		
+		if (name == null && !otherNames.isEmpty()) {
+			// get primary name and remove it from savedNames
+			final Iterator<String> it = otherNames.iterator();
+			assert it.hasNext();
+			primaryName = Optional.of(it.next());
+			otherNames.remove(primaryName.get());
+		} else {
+			primaryName = Optional.ofNullable(name);
+		}
+		
+		return new NameSymbol(primaryName, Optional.ofNullable(symbol),
+				otherNames);
+	}
+	
+	/**
+	 * Gets a {@code NameSymbol} with a primary name, a symbol and no other
+	 * names.
+	 * 
+	 * @param name   name to use
+	 * @param symbol symbol to use
+	 * @return NameSymbol instance
+	 * @since 2019-10-21
+	 * @throws NullPointerException if name or symbol is null
+	 */
+	public static final NameSymbol of(final String name, final String symbol) {
+		return new NameSymbol(Optional.of(name), Optional.of(symbol),
+				new HashSet<>());
+	}
+	
+	/**
+	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional
+	 * names.
+	 * 
+	 * @param name       name to use
+	 * @param symbol     symbol to use
+	 * @param otherNames other names to use
+	 * @return NameSymbol instance
+	 * @since 2019-10-21
+	 * @throws NullPointerException if any argument is null
+	 */
+	public static final NameSymbol of(final String name, final String symbol,
+			final Set<String> otherNames) {
+		return new NameSymbol(Optional.of(name), Optional.of(symbol),
+				new HashSet<>(Objects.requireNonNull(otherNames,
+						"otherNames must not be null.")));
+	}
+	
+	/**
+	 * h * Gets a {@code NameSymbol} with a primary name, a symbol and additional
+	 * names.
+	 * 
+	 * @param name       name to use
+	 * @param symbol     symbol to use
+	 * @param otherNames other names to use
+	 * @return NameSymbol instance
+	 * @since 2019-10-21
+	 * @throws NullPointerException if any argument is null
+	 */
+	public static final NameSymbol of(final String name, final String symbol,
+			final String... otherNames) {
+		return new NameSymbol(Optional.of(name), Optional.of(symbol),
+				new HashSet<>(Arrays.asList(Objects.requireNonNull(otherNames,
+						"otherNames must not be null."))));
+	}
+	
+	/**
+	 * Gets a {@code NameSymbol} with a primary name, no symbol, and no other
+	 * names.
+	 * 
+	 * @param name name to use
+	 * @return NameSymbol instance
+	 * @since 2019-10-21
+	 * @throws NullPointerException if name is null
+	 */
+	public static final NameSymbol ofName(final String name) {
+		return new NameSymbol(Optional.of(name), Optional.empty(),
+				new HashSet<>());
+	}
+	
+	/**
+	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional
+	 * names.
+	 * <p>
+	 * If any argument is null, this static factory replaces it with an empty
+	 * Optional or empty Set.
+	 * <p>
+	 * If {@code name} is null and {@code otherNames} is not empty, a primary
+	 * name will be picked from {@code otherNames}. This name will not appear in
+	 * getOtherNames().
+	 * 
+	 * @param name       name to use
+	 * @param symbol     symbol to use
+	 * @param otherNames other names to use
+	 * @return NameSymbol instance
+	 * @since 2019-11-26
+	 */
+	public static final NameSymbol ofNullable(final String name,
+			final String symbol, final Set<String> otherNames) {
+		return NameSymbol.create(name, symbol,
+				otherNames == null ? new HashSet<>() : new HashSet<>(otherNames));
+	}
+	
+	/**
+	 * h * Gets a {@code NameSymbol} with a primary name, a symbol and additional
+	 * names.
+	 * <p>
+	 * If any argument is null, this static factory replaces it with an empty
+	 * Optional or empty Set.
+	 * <p>
+	 * If {@code name} is null and {@code otherNames} is not empty, a primary
+	 * name will be picked from {@code otherNames}. This name will not appear in
+	 * getOtherNames().
+	 * 
+	 * @param name       name to use
+	 * @param symbol     symbol to use
+	 * @param otherNames other names to use
+	 * @return NameSymbol instance
+	 * @since 2019-11-26
+	 */
+	public static final NameSymbol ofNullable(final String name,
+			final String symbol, final String... otherNames) {
+		return create(name, symbol, otherNames == null ? new HashSet<>()
+				: new HashSet<>(Arrays.asList(otherNames)));
+	}
+	
+	/**
+	 * Gets a {@code NameSymbol} with a symbol and no names.
+	 * 
+	 * @param symbol symbol to use
+	 * @return NameSymbol instance
+	 * @since 2019-10-21
+	 * @throws NullPointerException if symbol is null
+	 */
+	public static final NameSymbol ofSymbol(final String symbol) {
+		return new NameSymbol(Optional.empty(), Optional.of(symbol),
+				new HashSet<>());
+	}
+	
+	private final Optional<String> primaryName;
+	private final Optional<String> symbol;
+	
+	private final Set<String> otherNames;
+	
+	/**
+	 * Creates the {@code NameSymbol}.
+	 * 
+	 * @param primaryName primary name of unit
+	 * @param symbol      symbol used to represent unit
+	 * @param otherNames  other names and/or spellings, should be a mutable copy
+	 *                    of the argument
+	 * @since 2019-10-21
+	 */
+	private NameSymbol(final Optional<String> primaryName,
+			final Optional<String> symbol, final Set<String> otherNames) {
+		this.primaryName = primaryName;
+		this.symbol = symbol;
+		otherNames.remove(null);
+		this.otherNames = Collections.unmodifiableSet(otherNames);
+		
+		if (this.primaryName.isEmpty()) {
+			assert this.otherNames.isEmpty();
+		}
+	}
+	
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (!(obj instanceof NameSymbol))
+			return false;
+		final NameSymbol other = (NameSymbol) obj;
+		if (this.otherNames == null) {
+			if (other.otherNames != null)
+				return false;
+		} else if (!this.otherNames.equals(other.otherNames))
+			return false;
+		if (this.primaryName == null) {
+			if (other.primaryName != null)
+				return false;
+		} else if (!this.primaryName.equals(other.primaryName))
+			return false;
+		if (this.symbol == null) {
+			if (other.symbol != null)
+				return false;
+		} else if (!this.symbol.equals(other.symbol))
+			return false;
+		return true;
+	}
+	
+	/**
+	 * @return otherNames
+	 * @since 2019-10-21
+	 */
+	public final Set<String> getOtherNames() {
+		return this.otherNames;
+	}
+	
+	/**
+	 * @return primaryName
+	 * @since 2019-10-21
+	 */
+	public final Optional<String> getPrimaryName() {
+		return this.primaryName;
+	}
+	
+	/**
+	 * @return symbol
+	 * @since 2019-10-21
+	 */
+	public final Optional<String> getSymbol() {
+		return this.symbol;
+	}
+	
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result
+				+ (this.otherNames == null ? 0 : this.otherNames.hashCode());
+		result = prime * result
+				+ (this.primaryName == null ? 0 : this.primaryName.hashCode());
+		result = prime * result
+				+ (this.symbol == null ? 0 : this.symbol.hashCode());
+		return result;
+	}
+	
+	/**
+	 * @return true iff this {@code NameSymbol} contains no names or symbols.
+	 */
+	public final boolean isEmpty() {
+		// if primaryName is empty, otherNames must also be empty
+		return this.primaryName.isEmpty() && this.symbol.isEmpty();
+	}
+	
+	@Override
+	public String toString() {
+		if (this.isEmpty())
+			return "NameSymbol.EMPTY";
+		else if (this.primaryName.isPresent() && this.symbol.isPresent())
+			return this.primaryName.orElseThrow() + " ("
+					+ this.symbol.orElseThrow() + ")";
+		else
+			return this.primaryName.orElseGet(this.symbol::orElseThrow);
+	}
+	
+	/**
+	 * Creates and returns a copy of this {@code NameSymbol} with the provided
+	 * extra name. If this {@code NameSymbol} has a primary name, the provided
+	 * name will become an other name, otherwise it will become the primary name.
+	 *
+	 * @since 2022-04-19
+	 */
+	public final NameSymbol withExtraName(String name) {
+		if (this.primaryName.isPresent()) {
+			final var otherNames = new HashSet<>(this.otherNames);
+			otherNames.add(name);
+			return NameSymbol.ofNullable(this.primaryName.orElse(null),
+					this.symbol.orElse(null), otherNames);
+		} else
+			return NameSymbol.ofNullable(name, this.symbol.orElse(null));
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/sevenUnits/utils/Nameable.java b/src/main/java/sevenUnits/utils/Nameable.java
new file mode 100644
index 0000000..e469d04
--- /dev/null
+++ b/src/main/java/sevenUnits/utils/Nameable.java
@@ -0,0 +1,79 @@
+/**
+ * Copyright (C) 2020 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 sevenUnits.utils;
+
+import java.util.Optional;
+import java.util.Set;
+
+/**
+ * An object that can hold one or more names, and possibly a symbol. The name
+ * and symbol data should be immutable.
+ *
+ * @since 2020-09-07
+ */
+public interface Nameable {
+	/**
+	 * @return a name for the object - if there's a primary name, it's that,
+	 *         otherwise the symbol, otherwise "Unnamed"
+	 * @since 2022-02-26
+	 */
+	default String getName() {
+		final NameSymbol ns = this.getNameSymbol();
+		return ns.getPrimaryName().or(ns::getSymbol).orElse("Unnamed");
+	}
+	
+	/**
+	 * @return a {@code NameSymbol} that contains this object's primary name,
+	 *         symbol and other names
+	 * @since 2020-09-07
+	 */
+	NameSymbol getNameSymbol();
+	
+	/**
+	 * @return set of alternate names
+	 * @since 2020-09-07
+	 */
+	default Set<String> getOtherNames() {
+		return this.getNameSymbol().getOtherNames();
+	}
+	
+	/**
+	 * @return preferred name of object
+	 * @since 2020-09-07
+	 */
+	default Optional<String> getPrimaryName() {
+		return this.getNameSymbol().getPrimaryName();
+	}
+	
+	/**
+	 * @return a short name for the object - if there's a symbol, it's that,
+	 *         otherwise the symbol, otherwise "Unnamed"
+	 * @since 2022-02-26
+	 */
+	default String getShortName() {
+		final NameSymbol ns = this.getNameSymbol();
+		return ns.getSymbol().or(ns::getPrimaryName).orElse("Unnamed");
+	}
+	
+	/**
+	 * @return short symbol representing object
+	 * @since 2020-09-07
+	 */
+	default Optional<String> getSymbol() {
+		return this.getNameSymbol().getSymbol();
+	}
+}
diff --git a/src/main/java/sevenUnits/utils/ObjectProduct.java b/src/main/java/sevenUnits/utils/ObjectProduct.java
index 5b1b739..66bb773 100644
--- a/src/main/java/sevenUnits/utils/ObjectProduct.java
+++ b/src/main/java/sevenUnits/utils/ObjectProduct.java
@@ -33,7 +33,7 @@ import java.util.function.Function;
  * @author Adrien Hopkins
  * @since 2019-10-16
  */
-public final class ObjectProduct<T> {
+public class ObjectProduct<T> implements Nameable {
 	/**
 	 * Returns an empty ObjectProduct of a certain type
 	 * 
@@ -83,15 +83,32 @@ public final class ObjectProduct<T> {
 	final Map<T, Integer> exponents;
 	
 	/**
-	 * Creates the {@code ObjectProduct}.
+	 * The object's name and symbol
+	 */
+	private final NameSymbol nameSymbol;
+	
+	/**
+	 * Creates a {@code ObjectProduct} without a name/symbol.
 	 * 
 	 * @param exponents objects that make up this product
 	 * @since 2019-10-16
 	 */
-	private ObjectProduct(final Map<T, Integer> exponents) {
+	ObjectProduct(final Map<T, Integer> exponents) {
+		this(exponents, NameSymbol.EMPTY);
+	}
+	
+	/**
+	 * Creates the {@code ObjectProduct}.
+	 * 
+	 * @param exponents  objects that make up this product
+	 * @param nameSymbol name and symbol of object product
+	 * @since 2019-10-16
+	 */
+	ObjectProduct(final Map<T, Integer> exponents, NameSymbol nameSymbol) {
 		this.exponents = Collections.unmodifiableMap(
 				ConditionalExistenceCollections.conditionalExistenceMap(exponents,
 						e -> !Integer.valueOf(0).equals(e.getValue())));
+		this.nameSymbol = nameSymbol;
 	}
 	
 	/**
@@ -171,6 +188,11 @@ public final class ObjectProduct<T> {
 	}
 	
 	@Override
+	public NameSymbol getNameSymbol() {
+		return this.nameSymbol;
+	}
+	
+	@Override
 	public int hashCode() {
 		return Objects.hash(this.exponents);
 	}
@@ -235,16 +257,19 @@ public final class ObjectProduct<T> {
 	
 	/**
 	 * Converts this product to a string using the objects'
-	 * {@link Object#toString()} method. If objects have a long toString
-	 * representation, it is recommended to use {@link #toString(Function)}
-	 * instead to shorten the returned string.
+	 * {@link Object#toString()} method (or {@link Nameable#getShortName} if
+	 * available). If objects have a long toString representation, it is
+	 * recommended to use {@link #toString(Function)} instead to shorten the
+	 * returned string.
 	 * 
 	 * <p>
 	 * {@inheritDoc}
 	 */
 	@Override
 	public String toString() {
-		return this.toString(Object::toString);
+		return this
+				.toString(o -> o instanceof Nameable ? ((Nameable) o).getShortName()
+						: o.toString());
 	}
 	
 	/**
@@ -280,4 +305,13 @@ public final class ObjectProduct<T> {
 		
 		return positiveString + negativeString;
 	}
+	
+	/**
+	 * @return named version of this {@code ObjectProduct}, using data from
+	 *         {@code nameSymbol}
+	 * @since 2021-12-15
+	 */
+	public ObjectProduct<T> withName(NameSymbol nameSymbol) {
+		return new ObjectProduct<>(this.exponents, nameSymbol);
+	}
 }
diff --git a/src/main/java/sevenUnits/utils/SemanticVersionNumber.java b/src/main/java/sevenUnits/utils/SemanticVersionNumber.java
new file mode 100644
index 0000000..06417c5
--- /dev/null
+++ b/src/main/java/sevenUnits/utils/SemanticVersionNumber.java
@@ -0,0 +1,691 @@
+/**
+ * Copyright (C) 2022 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 sevenUnits.utils;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * A version number in the <a href="https://semver.org">Semantic Versioning</a>
+ * scheme
+ * <p>
+ * Each version number has three main parts:
+ * <ol>
+ * <li>The major version, which increments when backwards incompatible changes
+ * are made
+ * <li>The minor version, which increments when backwards compatible feature
+ * changes are made
+ * <li>The patch version, which increments when backwards compatible bug fixes
+ * are made
+ * </ol>
+ *
+ * @since 2022-02-19
+ */
+public final class SemanticVersionNumber
+		implements Comparable<SemanticVersionNumber> {
+	/**
+	 * A builder that can be used to create complex version numbers.
+	 * <p>
+	 * Note: None of this builder's methods tolerate null arguments, arrays
+	 * containing nulls, negative numbers, or non-alphanumeric identifiers. Nulls
+	 * throw NullPointerExceptions, everything else throws
+	 * IllegalArgumentException.
+	 *
+	 * @since 2022-02-19
+	 */
+	public static final class Builder {
+		private final int major;
+		private final int minor;
+		private final int patch;
+		private final List<String> preReleaseIdentifiers;
+		private final List<String> buildMetadata;
+		
+		/**
+		 * Creates a builder which can be used to create a
+		 * {@code SemanticVersionNumber}
+		 *
+		 * @param major major version number of final version
+		 * @param minor minor version number of final version
+		 * @param patch patch version number of final version
+		 * @since 2022-02-19
+		 */
+		private Builder(int major, int minor, int patch) {
+			this.major = major;
+			this.minor = minor;
+			this.patch = patch;
+			this.preReleaseIdentifiers = new ArrayList<>();
+			this.buildMetadata = new ArrayList<>();
+		}
+		
+		/**
+		 * @return version number created by this builder
+		 * @since 2022-02-19
+		 */
+		public SemanticVersionNumber build() {
+			return new SemanticVersionNumber(this.major, this.minor, this.patch,
+					this.preReleaseIdentifiers, this.buildMetadata);
+		}
+		
+		/**
+		 * Adds one or more build metadata identifiers
+		 *
+		 * @param identifiers build metadata
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder buildMetadata(List<String> identifiers) {
+			Objects.requireNonNull(identifiers, "identifiers may not be null");
+			for (final String identifier : identifiers) {
+				Objects.requireNonNull(identifier, "identifier may not be null");
+				if (!VALID_IDENTIFIER.matcher(identifier).matches())
+					throw new IllegalArgumentException(
+							String.format("Invalid identifier \"%s\"", identifier));
+				this.buildMetadata.add(identifier);
+			}
+			return this;
+		}
+		
+		/**
+		 * Adds one or more build metadata identifiers
+		 *
+		 * @param identifiers build metadata
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder buildMetadata(String... identifiers) {
+			Objects.requireNonNull(identifiers, "identifiers may not be null");
+			for (final String identifier : identifiers) {
+				Objects.requireNonNull(identifier, "identifier may not be null");
+				if (!VALID_IDENTIFIER.matcher(identifier).matches())
+					throw new IllegalArgumentException(
+							String.format("Invalid identifier \"%s\"", identifier));
+				this.buildMetadata.add(identifier);
+			}
+			return this;
+		}
+		
+		@Override
+		public boolean equals(Object obj) {
+			if (this == obj)
+				return true;
+			if (!(obj instanceof Builder))
+				return false;
+			final Builder other = (Builder) obj;
+			return Objects.equals(this.buildMetadata, other.buildMetadata)
+					&& this.major == other.major && this.minor == other.minor
+					&& this.patch == other.patch && Objects.equals(
+							this.preReleaseIdentifiers, other.preReleaseIdentifiers);
+		}
+		
+		@Override
+		public int hashCode() {
+			return Objects.hash(this.buildMetadata, this.major, this.minor,
+					this.patch, this.preReleaseIdentifiers);
+		}
+		
+		/**
+		 * Adds one or more numeric identifiers to the version number
+		 *
+		 * @param identifiers pre-release identifier(s) to add
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder preRelease(int... identifiers) {
+			Objects.requireNonNull(identifiers, "identifiers may not be null");
+			for (final int identifier : identifiers) {
+				if (identifier < 0)
+					throw new IllegalArgumentException(
+							"Numeric identifiers may not be negative");
+				this.preReleaseIdentifiers.add(Integer.toString(identifier));
+			}
+			return this;
+		}
+		
+		/**
+		 * Adds one or more pre-release identifier(s) to the version number
+		 *
+		 * @param identifiers pre-release identifier(s) to add
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder preRelease(List<String> identifiers) {
+			Objects.requireNonNull(identifiers, "identifiers may not be null");
+			for (final String identifier : identifiers) {
+				Objects.requireNonNull(identifier, "identifier may not be null");
+				if (!VALID_IDENTIFIER.matcher(identifier).matches())
+					throw new IllegalArgumentException(
+							String.format("Invalid identifier \"%s\"", identifier));
+				this.preReleaseIdentifiers.add(identifier);
+			}
+			return this;
+		}
+		
+		/**
+		 * Adds one or more pre-release identifier(s) to the version number
+		 *
+		 * @param identifiers pre-release identifier(s) to add
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder preRelease(String... identifiers) {
+			Objects.requireNonNull(identifiers, "identifiers may not be null");
+			for (final String identifier : identifiers) {
+				Objects.requireNonNull(identifier, "identifier may not be null");
+				if (!VALID_IDENTIFIER.matcher(identifier).matches())
+					throw new IllegalArgumentException(
+							String.format("Invalid identifier \"%s\"", identifier));
+				this.preReleaseIdentifiers.add(identifier);
+			}
+			return this;
+		}
+		
+		/**
+		 * Adds a string identifier and an integer identifer to pre-release data
+		 *
+		 * @param identifier1 first identifier
+		 * @param identifier2 second identifier
+		 * @return this builder
+		 * @since 2022-02-19
+		 */
+		public Builder preRelease(String identifier1, int identifier2) {
+			Objects.requireNonNull(identifier1, "identifier1 may not be null");
+			if (!VALID_IDENTIFIER.matcher(identifier1).matches())
+				throw new IllegalArgumentException(
+						String.format("Invalid identifier \"%s\"", identifier1));
+			if (identifier2 < 0)
+				throw new IllegalArgumentException(
+						"Integer identifier cannot be negative");
+			this.preReleaseIdentifiers.add(identifier1);
+			this.preReleaseIdentifiers.add(Integer.toString(identifier2));
+			return this;
+		}
+		
+		@Override
+		public String toString() {
+			return "Semantic Version Builder: " + this.build().toString();
+		}
+	}
+	
+	/**
+	 * An alternative comparison method for version numbers. This uses the
+	 * version's natural order, but the build metadata will be compared (using
+	 * the same rules as pre-release identifiers) if everything else is equal.
+	 * <p>
+	 * This ordering is consistent with equals, unlike
+	 * {@code SemanticVersionNumber}'s natural ordering.
+	 */
+	public static final Comparator<SemanticVersionNumber> BUILD_METADATA_COMPARATOR = new Comparator<>() {
+		@Override
+		public int compare(SemanticVersionNumber o1, SemanticVersionNumber o2) {
+			Objects.requireNonNull(o1, "o1 may not be null");
+			Objects.requireNonNull(o2, "o2 may not be null");
+			final int naturalComparison = o1.compareTo(o2);
+			if (naturalComparison == 0)
+				return SemanticVersionNumber.compareIdentifiers(o1.buildMetadata,
+						o2.buildMetadata);
+			else
+				return naturalComparison;
+		};
+	};
+	
+	/** The alphanumeric pattern all identifiers must follow */
+	private static final Pattern VALID_IDENTIFIER = Pattern
+			.compile("[0-9A-Za-z-]+");
+	
+	/** The numeric pattern which causes special behaviour */
+	private static final Pattern NUMERIC_IDENTIFER = Pattern.compile("[0-9]+");
+	
+	/** The pattern for a version number */
+	private static final Pattern VERSION_NUMBER = Pattern
+			.compile("(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)" // main
+					// version
+					+ "(?:-([0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?" // pre-release
+					+ "(?:\\+([0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?"); // build data
+	
+	/**
+	 * Creates a builder that can be used to create a version number
+	 *
+	 * @param major major version number of final version
+	 * @param minor minor version number of final version
+	 * @param patch patch version number of final version
+	 * @return version number builder
+	 * @throws IllegalArgumentException if any argument is negative
+	 * @since 2022-02-19
+	 */
+	public static final SemanticVersionNumber.Builder builder(int major,
+			int minor, int patch) {
+		if (major < 0)
+			throw new IllegalArgumentException(
+					"Major version must be non-negative.");
+		if (minor < 0)
+			throw new IllegalArgumentException(
+					"Minor version must be non-negative.");
+		if (patch < 0)
+			throw new IllegalArgumentException(
+					"Patch version must be non-negative.");
+		return new SemanticVersionNumber.Builder(major, minor, patch);
+	}
+	
+	/**
+	 * Compares two lists of strings based on SemVer's precedence rules
+	 *
+	 * @param a first list
+	 * @param b second list
+	 * @return result of comparison as in a comparator
+	 * @see Comparator
+	 * @since 2022-02-20
+	 */
+	private static final int compareIdentifiers(List<String> a, List<String> b) {
+		// test pre-release size
+		final int aSize = a.size();
+		final int bSize = b.size();
+		
+		// no identifiers is greater than any identifiers
+		if (aSize != 0 && bSize == 0)
+			return -1;
+		else if (aSize == 0 && bSize != 0)
+			return 1;
+		
+		// test identifiers one by one
+		for (int i = 0; i < Math.min(aSize, bSize); i++) {
+			final String aElement = a.get(i);
+			final String bElement = b.get(i);
+			
+			if (NUMERIC_IDENTIFER.matcher(aElement).matches()) {
+				if (NUMERIC_IDENTIFER.matcher(bElement).matches()) {
+					// both are numbers, compare them
+					final int aNumber = Integer.parseInt(aElement);
+					final int bNumber = Integer.parseInt(bElement);
+					
+					if (aNumber < bNumber)
+						return -1;
+					else if (aNumber > bNumber)
+						return 1;
+				} else
+					// aElement is a number and bElement is not a number
+					// by the rules, a goes before b
+					return -1;
+			} else {
+				if (NUMERIC_IDENTIFER.matcher(bElement).matches())
+					// aElement is not a number but bElement is
+					// by the rules, a goes after b
+					return 1;
+				else {
+					// both are not numbers, compare them
+					final int comparison = aElement.compareTo(bElement);
+					if (comparison != 0)
+						return comparison;
+				}
+			}
+		}
+		
+		// we just tested the stuff that's in common, maybe someone has more
+		if (aSize < bSize)
+			return -1;
+		else if (aSize > bSize)
+			return 1;
+		else
+			return 0;
+	}
+	
+	/**
+	 * Gets a version number from a string in the official format
+	 *
+	 * @param versionString string to parse
+	 * @return {@code SemanticVersionNumber} instance
+	 * @since 2022-02-19
+	 * @see {@link #toString}
+	 */
+	public static final SemanticVersionNumber fromString(String versionString) {
+		// parse & validate version string
+		Objects.requireNonNull(versionString, "versionString may not be null");
+		final Matcher m = VERSION_NUMBER.matcher(versionString);
+		if (!m.matches())
+			throw new IllegalArgumentException(
+					String.format("Provided string \"%s\" is not a version number",
+							versionString));
+		
+		// main parts
+		final int major = Integer.parseInt(m.group(1));
+		final int minor = Integer.parseInt(m.group(2));
+		final int patch = Integer.parseInt(m.group(3));
+		
+		// pre release
+		final List<String> preRelease;
+		if (m.group(4) == null) {
+			preRelease = List.of();
+		} else {
+			preRelease = Arrays.asList(m.group(4).split("\\."));
+		}
+		
+		// build metadata
+		final List<String> buildMetadata;
+		if (m.group(5) == null) {
+			buildMetadata = List.of();
+		} else {
+			buildMetadata = Arrays.asList(m.group(5).split("\\."));
+		}
+		
+		// return number
+		return new SemanticVersionNumber(major, minor, patch, preRelease,
+				buildMetadata);
+	}
+	
+	/**
+	 * Tests whether a string is a valid Semantic Version string
+	 * 
+	 * @param versionString string to test
+	 * @return true iff string is valid
+	 * @since 2022-02-19
+	 */
+	public static final boolean isValidVersionString(String versionString) {
+		return VERSION_NUMBER.matcher(versionString).matches();
+	}
+	
+	/**
+	 * Creates a simple pre-release version number of the form
+	 * MAJOR.MINOR.PATH-TYPE.NUMBER (e.g. 1.2.3-alpha.4).
+	 *
+	 * @param major            major version number
+	 * @param minor            minor version number
+	 * @param patch            patch version number
+	 * @param preReleaseType   first pre-release element
+	 * @param preReleaseNumber second pre-release element
+	 * @return {@code SemanticVersionNumber} instance
+	 * @throws IllegalArgumentException if any argument is negative or if the
+	 *                                  preReleaseType is null, empty or not
+	 *                                  alphanumeric (0-9, A-Z, a-z, - only)
+	 * @since 2022-02-19
+	 */
+	public static final SemanticVersionNumber preRelease(int major, int minor,
+			int patch, String preReleaseType, int preReleaseNumber) {
+		if (major < 0)
+			throw new IllegalArgumentException(
+					"Major version must be non-negative.");
+		if (minor < 0)
+			throw new IllegalArgumentException(
+					"Minor version must be non-negative.");
+		if (patch < 0)
+			throw new IllegalArgumentException(
+					"Patch version must be non-negative.");
+		Objects.requireNonNull(preReleaseType, "preReleaseType may not be null");
+		if (!VALID_IDENTIFIER.matcher(preReleaseType).matches())
+			throw new IllegalArgumentException(
+					String.format("Invalid identifier \"%s\".", preReleaseType));
+		if (preReleaseNumber < 0)
+			throw new IllegalArgumentException(
+					"Pre-release number must be non-negative.");
+		return new SemanticVersionNumber(major, minor, patch,
+				List.of(preReleaseType, Integer.toString(preReleaseNumber)),
+				List.of());
+	}
+	
+	/**
+	 * Creates a {@code SemanticVersionNumber} instance without pre-release
+	 * identifiers or build metadata.
+	 * <p>
+	 * Note: this method allows you to create versions with major version number
+	 * 0, even though these versions would not be considered stable.
+	 *
+	 * @param major major version number
+	 * @param minor minor version number
+	 * @param patch patch version number
+	 * @return {@code SemanticVersionNumber} instance
+	 * @throws IllegalArgumentException if any argument is negative
+	 * @since 2022-02-19
+	 */
+	public static final SemanticVersionNumber stableVersion(int major, int minor,
+			int patch) {
+		if (major < 0)
+			throw new IllegalArgumentException(
+					"Major version must be non-negative.");
+		if (minor < 0)
+			throw new IllegalArgumentException(
+					"Minor version must be non-negative.");
+		if (patch < 0)
+			throw new IllegalArgumentException(
+					"Patch version must be non-negative.");
+		return new SemanticVersionNumber(major, minor, patch, List.of(),
+				List.of());
+	}
+	
+	// parts of the version number
+	private final int major;
+	private final int minor;
+	private final int patch;
+	private final List<String> preReleaseIdentifiers;
+	private final List<String> buildMetadata;
+	
+	/**
+	 * Creates a version number
+	 *
+	 * @param major                 major version number
+	 * @param minor                 minor version number
+	 * @param patch                 patch version number
+	 * @param preReleaseIdentifiers pre-release version data
+	 * @param buildMetadata         build metadata
+	 * @since 2022-02-19
+	 */
+	private SemanticVersionNumber(int major, int minor, int patch,
+			List<String> preReleaseIdentifiers, List<String> buildMetadata) {
+		this.major = major;
+		this.minor = minor;
+		this.patch = patch;
+		this.preReleaseIdentifiers = preReleaseIdentifiers;
+		this.buildMetadata = buildMetadata;
+	}
+	
+	/**
+	 * @return build metadata (empty if there is none)
+	 * @since 2022-02-19
+	 */
+	public List<String> buildMetadata() {
+		return Collections.unmodifiableList(this.buildMetadata);
+	}
+	
+	/**
+	 * Compares two version numbers according to the official Semantic Versioning
+	 * order.
+	 * <p>
+	 * Note: this ordering is not consistent with equals. Specifically, two
+	 * versions that are identical except for their build metadata will be
+	 * considered different by equals but the same by this method. This is
+	 * required to follow the official Semantic Versioning specification.
+	 * <p>
+	 */
+	@Override
+	public int compareTo(SemanticVersionNumber o) {
+		// test the three big numbers in order first
+		if (this.major < o.major)
+			return -1;
+		else if (this.major > o.major)
+			return 1;
+		
+		if (this.minor < o.minor)
+			return -1;
+		else if (this.minor > o.minor)
+			return 1;
+		
+		if (this.patch < o.patch)
+			return -1;
+		else if (this.patch > o.patch)
+			return 1;
+			
+		// now we just compare pre-release identifiers
+		// (remember: build metadata is ignored)
+		return SemanticVersionNumber.compareIdentifiers(this.preReleaseIdentifiers,
+				o.preReleaseIdentifiers);
+	}
+	
+	/**
+	 * Determines the compatibility of code written for this version to
+	 * {@code other}. More specifically:
+	 * <p>
+	 * If this function returns <b>true</b>, then there should be no problems
+	 * upgrading code written for this version to version {@code other} as long
+	 * as:
+	 * <ul>
+	 * <li>Semantic Versioning is being used properly
+	 * <li>Your code doesn't depend on unintended features (if it does, it isn't
+	 * necessarily compatible with any other version)
+	 * </ul>
+	 * If this function returns <b>false</b>, you may have to change your code to
+	 * upgrade it to {@code other}
+	 * 
+	 * <p>
+	 * Two version numbers that are identical (ignoring build metadata) are
+	 * always compatible. Different version numbers are compatible as long as:
+	 * <ul>
+	 * <li>The major version number is not 0 (if it is, the API is considered
+	 * unstable and any upgrade can be backwards compatible)
+	 * <li>The major version number is the same (changing the major version
+	 * number implies bacwards incompatible changes)
+	 * <li>This version comes before the other one in the official precedence
+	 * order (downgrading can remove features you depend on)
+	 * </ul>
+	 *
+	 * @param other version to compare with
+	 * @return true if you can definitely upgrade to {@code other} without
+	 *         changing code
+	 * @since 2022-02-20
+	 */
+	public boolean compatibleWith(SemanticVersionNumber other) {
+		Objects.requireNonNull(other, "other may not be null");
+		
+		return this.compareTo(other) == 0 || this.major != 0
+				&& this.major == other.major && this.compareTo(other) < 0;
+	}
+	
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (!(obj instanceof SemanticVersionNumber))
+			return false;
+		final SemanticVersionNumber other = (SemanticVersionNumber) obj;
+		if (this.buildMetadata == null) {
+			if (other.buildMetadata != null)
+				return false;
+		} else if (!this.buildMetadata.equals(other.buildMetadata))
+			return false;
+		if (this.major != other.major)
+			return false;
+		if (this.minor != other.minor)
+			return false;
+		if (this.patch != other.patch)
+			return false;
+		if (this.preReleaseIdentifiers == null) {
+			if (other.preReleaseIdentifiers != null)
+				return false;
+		} else if (!this.preReleaseIdentifiers
+				.equals(other.preReleaseIdentifiers))
+			return false;
+		return true;
+	}
+	
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result
+				+ (this.buildMetadata == null ? 0 : this.buildMetadata.hashCode());
+		result = prime * result + this.major;
+		result = prime * result + this.minor;
+		result = prime * result + this.patch;
+		result = prime * result + (this.preReleaseIdentifiers == null ? 0
+				: this.preReleaseIdentifiers.hashCode());
+		return result;
+	}
+	
+	/**
+	 * @return true iff this version is stable (major version > 0 and not a
+	 *         pre-release)
+	 * @since 2022-02-19
+	 */
+	public boolean isStable() {
+		return this.major > 0 && this.preReleaseIdentifiers.isEmpty();
+	}
+	
+	/**
+	 * @return the MAJOR version number, incremented when you make backwards
+	 *         incompatible API changes
+	 * @since 2022-02-19
+	 */
+	public int majorVersion() {
+		return this.major;
+	}
+	
+	/**
+	 * @return the MINOR version number, incremented when you add backwards
+	 *         compatible functionality
+	 * @since 2022-02-19
+	 */
+	public int minorVersion() {
+		return this.minor;
+	}
+	
+	/**
+	 * @return the PATCH version number, incremented when you make backwards
+	 *         compatible bug fixes
+	 * @since 2022-02-19
+	 */
+	public int patchVersion() {
+		return this.patch;
+	}
+	
+	/**
+	 * @return identifiers describing this pre-release (empty if not a
+	 *         pre-release)
+	 * @since 2022-02-19
+	 */
+	public List<String> preReleaseIdentifiers() {
+		return Collections.unmodifiableList(this.preReleaseIdentifiers);
+	}
+	
+	/**
+	 * Converts a version number to a string using the official SemVer format.
+	 * The core of a version is MAJOR.MINOR.PATCH, without zero-padding. If
+	 * pre-release identifiers are present, they are separated by periods and
+	 * added after a '-'. If build metadata is present, it is separated by
+	 * periods and added after a '+'. Pre-release identifiers go before version
+	 * metadata.
+	 * <p>
+	 * For example, the version with major number 3, minor number 2, patch number
+	 * 1, pre-release identifiers "alpha" and "1" and build metadata "2022-02-19"
+	 * has a string representation "3.2.1-alpha.1+2022-02-19".
+	 * 
+	 * @see <a href="https://semver.org">The official SemVer specification</a>
+	 */
+	@Override
+	public String toString() {
+		String versionString = String.format("%d.%d.%d", this.major, this.minor,
+				this.patch);
+		if (!this.preReleaseIdentifiers.isEmpty()) {
+			versionString += "-" + String.join(".", this.preReleaseIdentifiers);
+		}
+		if (!this.buildMetadata.isEmpty()) {
+			versionString += "+" + String.join(".", this.buildMetadata);
+		}
+		return versionString;
+	}
+}
diff --git a/src/main/java/sevenUnits/utils/UncertainDouble.java b/src/main/java/sevenUnits/utils/UncertainDouble.java
index fe41104..ac523b3 100644
--- a/src/main/java/sevenUnits/utils/UncertainDouble.java
+++ b/src/main/java/sevenUnits/utils/UncertainDouble.java
@@ -46,6 +46,21 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 			+ "(?:\\s*(?:±|\\+-)\\s*" + NUMBER_REGEX + ")?");
 	
 	/**
+	 * Gets an UncertainDouble from a double string. The uncertainty of the
+	 * double will be one of the lowest decimal place of the number. For example,
+	 * "12345.678" will become 12345.678 ± 0.001.
+	 * 
+	 * @throws NumberFormatException if the argument is not a number
+	 *
+	 * @since 2022-04-18
+	 */
+	public static final UncertainDouble fromRoundedString(String s) {
+		final BigDecimal value = new BigDecimal(s);
+		final double uncertainty = Math.pow(10, -value.scale());
+		return UncertainDouble.of(value.doubleValue(), uncertainty);
+	}
+	
+	/**
 	 * Parses a string in the form of {@link UncertainDouble#toString(boolean)}
 	 * and returns the corresponding {@code UncertainDouble} instance.
 	 * <p>
@@ -348,7 +363,7 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 	 */
 	@Override
 	public final String toString() {
-		return this.toString(!this.isExact());
+		return this.toString(!this.isExact(), RoundingMode.HALF_EVEN);
 	}
 	
 	/**
@@ -379,7 +394,8 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 	 * 
 	 * @since 2020-09-07
 	 */
-	public final String toString(boolean showUncertainty) {
+	public final String toString(boolean showUncertainty,
+			RoundingMode roundingMode) {
 		String valueString, uncertaintyString;
 		
 		// generate the string representation of value and uncertainty
@@ -394,9 +410,9 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 			
 			final int displayScale = this.getDisplayScale();
 			final BigDecimal roundedUncertainty = bigUncertainty
-					.setScale(displayScale, RoundingMode.HALF_EVEN);
+					.setScale(displayScale, roundingMode);
 			final BigDecimal roundedValue = bigValue.setScale(displayScale,
-					RoundingMode.HALF_EVEN);
+					roundingMode);
 			
 			valueString = roundedValue.toString();
 			uncertaintyString = roundedUncertainty.toString();