Merge branch 'release-0.3.2'

9 files changed, 159 insertions, 121 deletions

diff --git a/src/main/java/sevenUnits/ProgramInfo.java b/src/main/java/sevenUnits/ProgramInfo.java
index 2a0edde..31e43c7 100644
--- a/src/main/java/sevenUnits/ProgramInfo.java
+++ b/src/main/java/sevenUnits/ProgramInfo.java
@@ -24,7 +24,7 @@ package sevenUnits;
  */
 public final class ProgramInfo {
 	
-	public static final String VERSION = "0.3.1";
+	public static final String VERSION = "0.3.2";
 	
 	private ProgramInfo() {}
 	
diff --git a/src/main/java/sevenUnits/unit/BritishImperial.java b/src/main/java/sevenUnits/unit/BritishImperial.java
index 81a3f2a..743beeb 100644
--- a/src/main/java/sevenUnits/unit/BritishImperial.java
+++ b/src/main/java/sevenUnits/unit/BritishImperial.java
@@ -37,7 +37,7 @@ public final class BritishImperial {
 		public static final LinearUnit ROOD = Length.ROD.times(Length.FURLONG);
 		public static final LinearUnit ACRE = Length.FURLONG.times(Length.CHAIN);
 	}
-
+	
 	/**
 	 * Imperial units that measure length
 	 * 
@@ -46,7 +46,8 @@ public final class BritishImperial {
 	 */
 	public static final class Length {
 		/**
-		 * According to the International Yard and Pound of 1959, a yard is defined as exactly 0.9144 metres.
+		 * According to the International Yard and Pound of 1959, a yard is
+		 * defined as exactly 0.9144 metres.
 		 */
 		public static final LinearUnit YARD = Metric.METRE.times(0.9144);
 		public static final LinearUnit FOOT = YARD.dividedBy(3);
@@ -56,15 +57,15 @@ public final class BritishImperial {
 		public static final LinearUnit FURLONG = CHAIN.times(10);
 		public static final LinearUnit MILE = FURLONG.times(8);
 		public static final LinearUnit LEAGUE = MILE.times(3);
-
+		
 		public static final LinearUnit NAUTICAL_MILE = Metric.METRE.times(1852);
 		public static final LinearUnit CABLE = NAUTICAL_MILE.dividedBy(10);
 		public static final LinearUnit FATHOM = CABLE.dividedBy(100);
-
+		
 		public static final LinearUnit ROD = YARD.times(5.5);
 		public static final LinearUnit LINK = ROD.dividedBy(25);
 	}
-
+	
 	/**
 	 * British Imperial units that measure mass.
 	 * 
@@ -82,7 +83,7 @@ public final class BritishImperial {
 		public static final LinearUnit LONG_TON = HUNDREDWEIGHT.times(20);
 		public static final LinearUnit SLUG = Metric.KILOGRAM.times(14.59390294);
 	}
-
+	
 	/**
 	 * British Imperial units that measure volume
 	 * 
@@ -90,27 +91,33 @@ public final class BritishImperial {
 	 * @since 2019-11-08
 	 */
 	public static final class Volume {
-		public static final LinearUnit FLUID_OUNCE = Metric.LITRE.withPrefix(Metric.MILLI).times(28.4130625);
+		public static final LinearUnit FLUID_OUNCE = Metric.LITRE
+				.withPrefix(Metric.MILLI).times(28.4130625);
 		public static final LinearUnit GILL = FLUID_OUNCE.times(5);
 		public static final LinearUnit PINT = FLUID_OUNCE.times(20);
 		public static final LinearUnit QUART = PINT.times(2);
 		public static final LinearUnit GALLON = QUART.times(4);
 		public static final LinearUnit PECK = GALLON.times(2);
 		public static final LinearUnit BUSHEL = PECK.times(4);
-
+		
 		public static final LinearUnit CUBIC_INCH = Length.INCH.toExponent(3);
 		public static final LinearUnit CUBIC_FOOT = Length.FOOT.toExponent(3);
 		public static final LinearUnit CUBIC_YARD = Length.YARD.toExponent(3);
 		public static final LinearUnit ACRE_FOOT = Area.ACRE.times(Length.FOOT);
 	}
-
-	public static final LinearUnit OUNCE_FORCE = Mass.OUNCE.times(Metric.Constants.EARTH_GRAVITY);
-	public static final LinearUnit POUND_FORCE = Mass.POUND.times(Metric.Constants.EARTH_GRAVITY);
-
-	public static final LinearUnit BRITISH_THERMAL_UNIT = Metric.JOULE.times(1055.06);
+	
+	public static final LinearUnit OUNCE_FORCE = Mass.OUNCE
+			.times(Metric.Constants.EARTH_GRAVITY);
+	public static final LinearUnit POUND_FORCE = Mass.POUND
+			.times(Metric.Constants.EARTH_GRAVITY);
+	
+	public static final LinearUnit BRITISH_THERMAL_UNIT = Metric.JOULE
+			.times(1055.06);
 	public static final LinearUnit CALORIE = Metric.JOULE.times(4.184);
 	public static final LinearUnit KILOCALORIE = Metric.JOULE.times(4184);
-
-	public static final Unit FAHRENHEIT = Unit.fromConversionFunctions(Metric.KELVIN.getBase(),
-			tempK -> tempK * 1.8 - 459.67, tempF -> (tempF + 459.67) / 1.8);
+	
+	public static final Unit FAHRENHEIT = Unit
+			.fromConversionFunctions(Metric.KELVIN.getBase(),
+					tempK -> tempK * 1.8 - 459.67, tempF -> (tempF + 459.67) / 1.8)
+			.withName(NameSymbol.of("degrees Fahrenheit", "\u00B0F"));
 }
diff --git a/src/main/java/sevenUnits/unit/LinearUnitValue.java b/src/main/java/sevenUnits/unit/LinearUnitValue.java
index a36d568..a50e1f5 100644
--- a/src/main/java/sevenUnits/unit/LinearUnitValue.java
+++ b/src/main/java/sevenUnits/unit/LinearUnitValue.java
@@ -324,17 +324,18 @@ public final class LinearUnitValue {
 		
 		// get rounded strings
 		// if showUncertainty is true, add brackets around the string
-		final String valueString = showUncertainty ? "("
-				: "" + this.value.toString(showUncertainty)
-						+ (showUncertainty ? ")" : "");
-		final String baseValueString = showUncertainty ? "("
-				: "" + baseValue.toString(showUncertainty)
-						+ (showUncertainty ? ")" : "");
+		final String valueString = (showUncertainty ? "(" : "")
+				+ this.value.toString(showUncertainty)
+				+ (showUncertainty ? ")" : "");
+		final String baseValueString = (showUncertainty ? "(" : "")
+				+ baseValue.toString(showUncertainty)
+				+ (showUncertainty ? ")" : "");
 		
 		// create string
-		if (primaryName.isEmpty() && symbol.isEmpty())
+		if (chosenName == null)
 			return String.format("%s unnamed unit (= %s %s)", valueString,
-					baseValueString, this.unit.getBase());
+					baseValueString, this.unit.getBase()
+							.toString(unit -> unit.getSymbol().orElseThrow()));
 		else
 			return String.format("%s %s", valueString, chosenName);
 	}
diff --git a/src/main/java/sevenUnits/unit/UnitDatabase.java b/src/main/java/sevenUnits/unit/UnitDatabase.java
index b45d9cf..18ac619 100644
--- a/src/main/java/sevenUnits/unit/UnitDatabase.java
+++ b/src/main/java/sevenUnits/unit/UnitDatabase.java
@@ -243,7 +243,8 @@ public final class UnitDatabase {
 						return false;
 					else {
 						if (this.prefixNames.isEmpty())
-							return this.unitNamePosition >= this.unitNames.size() - 1;
+							return this.prefixCoordinates.isEmpty()
+									&& this.unitNamePosition < this.unitNames.size();
 						else
 							return true;
 					}
@@ -557,7 +558,8 @@ public final class UnitDatabase {
 						return false;
 					else {
 						if (this.prefixNames.isEmpty())
-							return this.unitNamePosition >= this.unitNames.size() - 1;
+							return this.prefixCoordinates.isEmpty()
+									&& this.unitNamePosition < this.unitNames.size();
 						else
 							return true;
 					}
@@ -1038,7 +1040,7 @@ public final class UnitDatabase {
 		@Override
 		public String toString() {
 			if (this.units.isEmpty() || this.prefixes.isEmpty())
-				return super.toString();
+				return new HashMap<>(this).toString();
 			else
 				return String.format(
 						"Infinite map of name-unit entries created from units %s and prefixes %s",
@@ -1161,7 +1163,7 @@ public final class UnitDatabase {
 	 * @return true if entry represents a removable duplicate entry of unitMap.
 	 * @since 2021-05-22
 	 */
-	private static boolean isRemovableDuplicate(Map<String, Unit> unitMap,
+	static boolean isRemovableDuplicate(Map<String, Unit> unitMap,
 			Entry<String, Unit> entry) {
 		for (final Entry<String, Unit> e : unitMap.entrySet()) {
 			final String name = e.getKey();
@@ -1344,10 +1346,10 @@ public final class UnitDatabase {
 		final String name = lineMatcher.group(1);
 		final String expression = lineMatcher.group(2);
 		
-		if (name.endsWith(" ")) {
-			System.err.printf("Warning - line %d's dimension name ends in a space",
-					lineCounter);
-		}
+		// if (name.endsWith(" ")) {
+		// System.err.printf("Warning - line %d's dimension name ends in a space",
+		// lineCounter);
+		// }
 		
 		// if expression is "!", search for an existing dimension
 		// if no unit found, throw an error
@@ -1360,7 +1362,7 @@ public final class UnitDatabase {
 			final ObjectProduct<BaseDimension> dimension;
 			try {
 				dimension = this.getDimensionFromExpression(expression);
-			} catch (final IllegalArgumentException e) {
+			} catch (final IllegalArgumentException | NoSuchElementException e) {
 				System.err.printf("Parsing error on line %d:%n", lineCounter);
 				throw e;
 			}
@@ -1427,10 +1429,11 @@ public final class UnitDatabase {
 		
 		final String expression = lineMatcher.group(2);
 		
-		if (name.endsWith(" ")) {
-			System.err.printf("Warning - line %d's unit name ends in a space",
-					lineCounter);
-		}
+		// this code should never occur
+		// if (name.endsWith(" ")) {
+		// System.err.printf("Warning - line %d's unit name ends in a space",
+		// lineCounter);
+		// }
 		
 		// if expression is "!", search for an existing unit
 		// if no unit found, throw an error
@@ -1443,7 +1446,8 @@ public final class UnitDatabase {
 				final UnitPrefix prefix;
 				try {
 					prefix = this.getPrefixFromExpression(expression);
-				} catch (final IllegalArgumentException e) {
+				} catch (final IllegalArgumentException
+						| NoSuchElementException e) {
 					System.err.printf("Parsing error on line %d:%n", lineCounter);
 					throw e;
 				}
@@ -1453,7 +1457,8 @@ public final class UnitDatabase {
 				final Unit unit;
 				try {
 					unit = this.getUnitFromExpression(expression);
-				} catch (final IllegalArgumentException e) {
+				} catch (final IllegalArgumentException
+						| NoSuchElementException e) {
 					System.err.printf("Parsing error on line %d:%n", lineCounter);
 					throw e;
 				}
@@ -1581,8 +1586,15 @@ public final class UnitDatabase {
 			}
 			
 			return base.toExponent(exponent);
+		} else {
+			final ObjectProduct<BaseDimension> dimension = this.dimensions
+					.get(name);
+			if (dimension == null)
+				throw new NoSuchElementException(
+						"No dimension with name \"" + name + "\".");
+			else
+				return dimension;
 		}
-		return this.dimensions.get(name);
 	}
 	
 	/**
@@ -1635,7 +1647,7 @@ public final class UnitDatabase {
 	 * @since 2019-03-22
 	 * @since v0.2.0
 	 */
-	private LinearUnit getLinearUnit(final String name) {
+	LinearUnit getLinearUnit(final String name) {
 		// see if I am using a function-unit like tempC(100)
 		Objects.requireNonNull(name, "name may not be null");
 		if (name.contains("(") && name.contains(")")) {
@@ -1670,7 +1682,7 @@ public final class UnitDatabase {
 	 * @return {@code LinearUnitValue} instance
 	 * @since 2020-08-04
 	 */
-	private LinearUnitValue getLinearUnitValue(final String name) {
+	LinearUnitValue getLinearUnitValue(final String name) {
 		try {
 			// try to parse it as a number - otherwise it is not a number!
 			final BigDecimal number = new BigDecimal(name);
@@ -1695,7 +1707,12 @@ public final class UnitDatabase {
 		try {
 			return UnitPrefix.valueOf(Double.parseDouble(name));
 		} catch (final NumberFormatException e) {
-			return this.prefixes.get(name);
+			final UnitPrefix prefix = this.prefixes.get(name);
+			if (prefix == null)
+				throw new NoSuchElementException(
+						"No prefix with name \"" + name + "\".");
+			else
+				return prefix;
 		}
 	}
 	
diff --git a/src/main/java/sevenUnits/unit/UnitValue.java b/src/main/java/sevenUnits/unit/UnitValue.java
index 2fedd81..f6d18f8 100644
--- a/src/main/java/sevenUnits/unit/UnitValue.java
+++ b/src/main/java/sevenUnits/unit/UnitValue.java
@@ -163,7 +163,8 @@ public final class UnitValue {
 		if (primaryName.isEmpty() && symbol.isEmpty()) {
 			final double baseValue = this.getUnit().convertToBase(this.getValue());
 			return String.format("%s unnamed unit (= %s %s)", this.getValue(),
-					baseValue, this.getUnit().getBase());
+					baseValue, this.getUnit().getBase()
+							.toString(unit -> unit.getSymbol().orElseThrow()));
 		} else {
 			final String unitName = symbol.orElse(primaryName.get());
 			return this.getValue() + " " + unitName;
diff --git a/src/main/java/sevenUnits/utils/ConditionalExistenceCollections.java b/src/main/java/sevenUnits/utils/ConditionalExistenceCollections.java
index 2adb579..bee4dd1 100644
--- a/src/main/java/sevenUnits/utils/ConditionalExistenceCollections.java
+++ b/src/main/java/sevenUnits/utils/ConditionalExistenceCollections.java
@@ -283,7 +283,7 @@ public final class ConditionalExistenceCollections {
 		
 		@Override
 		public Set<K> keySet() {
-			return conditionalExistenceSet(super.keySet(),
+			return conditionalExistenceSet(this.map.keySet(),
 					k -> this.entryExistenceCondition.test(this.getEntry(k)));
 		}
 		
diff --git a/src/main/java/sevenUnits/utils/ExpressionParser.java b/src/main/java/sevenUnits/utils/ExpressionParser.java
index 1d3d44d..941c2a4 100644
--- a/src/main/java/sevenUnits/utils/ExpressionParser.java
+++ b/src/main/java/sevenUnits/utils/ExpressionParser.java
@@ -461,10 +461,12 @@ public final class ExpressionParser<T> {
 	 * 
 	 * @param expression expression
 	 * @return expression in RPN
+	 * @throws IllegalArgumentException if expression is invalid (e.g.
+	 *                                  "{@code 3 *}")
 	 * @since 2019-03-17
 	 * @since v0.2.0
 	 */
-	private String convertExpressionToReversePolish(final String expression) {
+	String convertExpressionToReversePolish(final String expression) {
 		Objects.requireNonNull(expression, "expression must not be null.");
 		
 		final List<String> components = new ArrayList<>();
@@ -541,6 +543,9 @@ public final class ExpressionParser<T> {
 			switch (this
 					.getTokenType(components.get(highestPriorityOperatorPosition))) {
 			case UNARY_OPERATOR:
+				if (components.size() < 2)
+					throw new IllegalArgumentException(
+							"Invalid expression \"" + expression + "\"");
 				final String unaryOperator = components
 						.remove(highestPriorityOperatorPosition);
 				final String operand = components
@@ -549,6 +554,9 @@ public final class ExpressionParser<T> {
 						operand + " " + unaryOperator);
 				break;
 			case BINARY_OPERATOR:
+				if (components.size() < 3)
+					throw new IllegalArgumentException(
+							"Invalid expression \"" + expression + "\"");
 				final String binaryOperator = components
 						.remove(highestPriorityOperatorPosition);
 				final String operand1 = components
@@ -672,7 +680,7 @@ public final class ExpressionParser<T> {
 	 * @since 2019-03-14
 	 * @since v0.2.0
 	 */
-	private T parseReversePolishExpression(final String expression) {
+	T parseReversePolishExpression(final String expression) {
 		Objects.requireNonNull(expression, "expression must not be null.");
 		
 		final Deque<T> stack = new ArrayDeque<>();
diff --git a/src/main/java/sevenUnits/utils/ObjectProduct.java b/src/main/java/sevenUnits/utils/ObjectProduct.java
index 1dacb7d..5b1b739 100644
--- a/src/main/java/sevenUnits/utils/ObjectProduct.java
+++ b/src/main/java/sevenUnits/utils/ObjectProduct.java
@@ -27,8 +27,8 @@ import java.util.Set;
 import java.util.function.Function;
 
 /**
- * An immutable product of multiple objects of a type, such as base units. The objects can be multiplied and
- * exponentiated.
+ * An immutable product of multiple objects of a type, such as base units. The
+ * objects can be multiplied and exponentiated.
  * 
  * @author Adrien Hopkins
  * @since 2019-10-16
@@ -37,38 +37,35 @@ public final class ObjectProduct<T> {
 	/**
 	 * Returns an empty ObjectProduct of a certain type
 	 * 
-	 * @param <T>
-	 *            type of objects that can be multiplied
+	 * @param <T> type of objects that can be multiplied
 	 * @return empty product
 	 * @since 2019-10-16
 	 */
 	public static final <T> ObjectProduct<T> empty() {
 		return new ObjectProduct<>(new HashMap<>());
 	}
-
+	
 	/**
 	 * Gets an {@code ObjectProduct} from an object-to-integer mapping
 	 * 
-	 * @param <T>
-	 *            type of object in product
-	 * @param map
-	 *            map mapping objects to exponents
+	 * @param <T> type of object in product
+	 * @param map map mapping objects to exponents
 	 * @return object product
 	 * @since 2019-10-16
 	 */
-	public static final <T> ObjectProduct<T> fromExponentMapping(final Map<T, Integer> map) {
+	public static final <T> ObjectProduct<T> fromExponentMapping(
+			final Map<T, Integer> map) {
 		return new ObjectProduct<>(new HashMap<>(map));
 	}
-
+	
 	/**
-	 * Gets an ObjectProduct that has one of the inputted argument, and nothing else.
+	 * Gets an ObjectProduct that has one of the inputted argument, and nothing
+	 * else.
 	 * 
-	 * @param object
-	 *            object that will be in the product
+	 * @param object object that will be in the product
 	 * @return product
 	 * @since 2019-10-16
-	 * @throws NullPointerException
-	 *             if object is null
+	 * @throws NullPointerException if object is null
 	 */
 	public static final <T> ObjectProduct<T> oneOf(final T object) {
 		Objects.requireNonNull(object, "object must not be null.");
@@ -76,35 +73,34 @@ public final class ObjectProduct<T> {
 		map.put(object, 1);
 		return new ObjectProduct<>(map);
 	}
-
+	
 	/**
-	 * The objects that make up the product, mapped to their exponents. This map treats zero as null, and is immutable.
+	 * The objects that make up the product, mapped to their exponents. This map
+	 * treats zero as null, and is immutable.
 	 * 
 	 * @since 2019-10-16
 	 */
 	final Map<T, Integer> exponents;
-
+	
 	/**
 	 * Creates the {@code ObjectProduct}.
 	 * 
-	 * @param exponents
-	 *            objects that make up this product
+	 * @param exponents objects that make up this product
 	 * @since 2019-10-16
 	 */
 	private ObjectProduct(final Map<T, Integer> exponents) {
-		this.exponents = Collections.unmodifiableMap(ConditionalExistenceCollections.conditionalExistenceMap(exponents,
-				e -> !Integer.valueOf(0).equals(e.getValue())));
+		this.exponents = Collections.unmodifiableMap(
+				ConditionalExistenceCollections.conditionalExistenceMap(exponents,
+						e -> !Integer.valueOf(0).equals(e.getValue())));
 	}
-
+	
 	/**
 	 * Calculates the quotient of two products
 	 *
-	 * @param other
-	 *            other product
+	 * @param other other product
 	 * @return quotient of two products
 	 * @since 2019-10-16
-	 * @throws NullPointerException
-	 *             if other is null
+	 * @throws NullPointerException if other is null
 	 */
 	public ObjectProduct<T> dividedBy(final ObjectProduct<T> other) {
 		Objects.requireNonNull(other, "other must not be null.");
@@ -112,17 +108,17 @@ public final class ObjectProduct<T> {
 		final Set<T> objects = new HashSet<>();
 		objects.addAll(this.getBaseSet());
 		objects.addAll(other.getBaseSet());
-
+		
 		// get a list of all exponents
 		final Map<T, Integer> map = new HashMap<>(objects.size());
 		for (final T key : objects) {
 			map.put(key, this.getExponent(key) - other.getExponent(key));
 		}
-
+		
 		// create the product
 		return new ObjectProduct<>(map);
 	}
-
+	
 	// this method relies on the use of ZeroIsNullMap
 	@Override
 	public boolean equals(final Object obj) {
@@ -133,7 +129,7 @@ public final class ObjectProduct<T> {
 		final ObjectProduct<?> other = (ObjectProduct<?>) obj;
 		return Objects.equals(this.exponents, other.exponents);
 	}
-
+	
 	/**
 	 * @return immutable map mapping objects to exponents
 	 * @since 2019-10-16
@@ -141,30 +137,31 @@ public final class ObjectProduct<T> {
 	public Map<T, Integer> exponentMap() {
 		return this.exponents;
 	}
-
+	
 	/**
-	 * @return a set of all of the base objects with non-zero exponents that make up this dimension.
+	 * @return a set of all of the base objects with non-zero exponents that make
+	 *         up this dimension.
 	 * @since 2018-12-12
 	 * @since v0.1.0
 	 */
 	public final Set<T> getBaseSet() {
 		final Set<T> dimensions = new HashSet<>();
-
-		// add all dimensions with a nonzero exponent - zero exponents shouldn't be there in the first place
+		
+		// add all dimensions with a nonzero exponent - zero exponents shouldn't
+		// be there in the first place
 		for (final T dimension : this.exponents.keySet()) {
 			if (!this.exponents.get(dimension).equals(0)) {
 				dimensions.add(dimension);
 			}
 		}
-
+		
 		return dimensions;
 	}
-
+	
 	/**
 	 * Gets the exponent for a specific dimension.
 	 * 
-	 * @param dimension
-	 *            dimension to check
+	 * @param dimension dimension to check
 	 * @return exponent for that dimension
 	 * @since 2018-12-12
 	 * @since v0.1.0
@@ -172,14 +169,15 @@ public final class ObjectProduct<T> {
 	public int getExponent(final T dimension) {
 		return this.exponents.getOrDefault(dimension, 0);
 	}
-
+	
 	@Override
 	public int hashCode() {
 		return Objects.hash(this.exponents);
 	}
-
+	
 	/**
-	 * @return true if this product is a single object, i.e. it has one exponent of one and no other nonzero exponents
+	 * @return true if this product is a single object, i.e. it has one exponent
+	 *         of one and no other nonzero exponents
 	 * @since 2019-10-16
 	 */
 	public boolean isSingleObject() {
@@ -194,16 +192,14 @@ public final class ObjectProduct<T> {
 		}
 		return oneCount == 1 && !twoOrMore;
 	}
-
+	
 	/**
 	 * Multiplies this product by another
 	 *
-	 * @param other
-	 *            other product
+	 * @param other other product
 	 * @return product of two products
 	 * @since 2019-10-16
-	 * @throws NullPointerException
-	 *             if other is null
+	 * @throws NullPointerException if other is null
 	 */
 	public ObjectProduct<T> times(final ObjectProduct<T> other) {
 		Objects.requireNonNull(other, "other must not be null.");
@@ -211,22 +207,21 @@ public final class ObjectProduct<T> {
 		final Set<T> objects = new HashSet<>();
 		objects.addAll(this.getBaseSet());
 		objects.addAll(other.getBaseSet());
-
+		
 		// get a list of all exponents
 		final Map<T, Integer> map = new HashMap<>(objects.size());
 		for (final T key : objects) {
 			map.put(key, this.getExponent(key) + other.getExponent(key));
 		}
-
+		
 		// create the product
 		return new ObjectProduct<>(map);
 	}
-
+	
 	/**
 	 * Returns this product, but to an exponent
 	 * 
-	 * @param exponent
-	 *            exponent
+	 * @param exponent exponent
 	 * @return result of exponentiation
 	 * @since 2019-10-16
 	 */
@@ -237,11 +232,12 @@ public final class ObjectProduct<T> {
 		}
 		return new ObjectProduct<>(map);
 	}
-
+	
 	/**
-	 * 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.
+	 * 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.
 	 * 
 	 * <p>
 	 * {@inheritDoc}
@@ -250,35 +246,38 @@ public final class ObjectProduct<T> {
 	public String toString() {
 		return this.toString(Object::toString);
 	}
-
+	
 	/**
-	 * Converts this product to a string. The objects that make up this product are represented by
-	 * {@code objectToString}
+	 * Converts this product to a string. The objects that make up this product
+	 * are represented by {@code objectToString}
 	 * 
-	 * @param objectToString
-	 *            function to convert objects to strings
+	 * @param objectToString function to convert objects to strings
 	 * @return string representation of product
 	 * @since 2019-10-16
 	 */
 	public String toString(final Function<T, String> objectToString) {
 		final List<String> positiveStringComponents = new ArrayList<>();
 		final List<String> negativeStringComponents = new ArrayList<>();
-
+		
 		// for each base object that makes up this object, add it and its exponent
 		for (final T object : this.getBaseSet()) {
 			final int exponent = this.exponents.get(object);
-			if (exponent > 0) {
-				positiveStringComponents.add(String.format("%s^%d", objectToString.apply(object), exponent));
+			if (exponent > 1) {
+				positiveStringComponents.add(String.format("%s^%d",
+						objectToString.apply(object), exponent));
+			} else if (exponent == 1) {
+				positiveStringComponents.add(objectToString.apply(object));
 			} else if (exponent < 0) {
-				negativeStringComponents.add(String.format("%s^%d", objectToString.apply(object), -exponent));
+				negativeStringComponents.add(String.format("%s^%d",
+						objectToString.apply(object), -exponent));
 			}
 		}
-
+		
 		final String positiveString = positiveStringComponents.isEmpty() ? "1"
 				: String.join(" * ", positiveStringComponents);
 		final String negativeString = negativeStringComponents.isEmpty() ? ""
 				: " / " + String.join(" * ", negativeStringComponents);
-
+		
 		return positiveString + negativeString;
 	}
 }
diff --git a/src/main/java/sevenUnits/utils/UncertainDouble.java b/src/main/java/sevenUnits/utils/UncertainDouble.java
index 8fe4b31..fe41104 100644
--- a/src/main/java/sevenUnits/utils/UncertainDouble.java
+++ b/src/main/java/sevenUnits/utils/UncertainDouble.java
@@ -36,13 +36,14 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 	 */
 	public static final UncertainDouble ZERO = UncertainDouble.of(0, 0);
 	
+	static final String NUMBER_REGEX = "(\\d+(?:[\\.,]\\d+))";
+	
 	/**
 	 * A regular expression that can recognize toString forms
 	 */
-	private static final Pattern TO_STRING = Pattern
-			.compile("([a-zA-Z_0-9\\.\\,]+)" // a number
-					// optional "± [number]"
-					+ "(?:\\s*(?:±|\\+-)\\s*([a-zA-Z_0-9\\.\\,]+))?");
+	static final Pattern TO_STRING = Pattern.compile(NUMBER_REGEX
+			// optional "± [number]"
+			+ "(?:\\s*(?:±|\\+-)\\s*" + NUMBER_REGEX + ")?");
 	
 	/**
 	 * Parses a string in the form of {@link UncertainDouble#toString(boolean)}
@@ -60,10 +61,14 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 		Objects.requireNonNull(s, "s may not be null");
 		final Matcher matcher = TO_STRING.matcher(s);
 		
+		if (!matcher.matches())
+			throw new IllegalArgumentException(
+					"Could not parse stirng \"" + s + "\".");
+		
 		double value, uncertainty;
 		try {
 			value = Double.parseDouble(matcher.group(1));
-		} catch (IllegalStateException | NumberFormatException e) {
+		} catch (final NumberFormatException e) {
 			throw new IllegalArgumentException(
 					"String " + s + " not in correct format.");
 		}