Add ability to convert expression to sum of units

1 files changed, 341 insertions, 265 deletions

diff --git a/src/main/java/sevenUnitsGUI/Presenter.java b/src/main/java/sevenUnitsGUI/Presenter.java
index eba8438..8f99649 100644
--- a/src/main/java/sevenUnitsGUI/Presenter.java
+++ b/src/main/java/sevenUnitsGUI/Presenter.java
@@ -72,30 +72,7 @@ public final class Presenter {
 	private static final String DEFAULT_DIMENSIONS_FILEPATH = "/dimensionfile.txt";
 	/** The default place where exceptions are stored. */
 	private static final String DEFAULT_EXCEPTIONS_FILEPATH = "/metric_exceptions.txt";
-
-	private static final Path userConfigDir() {
-		if (System.getProperty("os.name").startsWith("Windows")) {
-			final String envFolder = System.getenv("LOCALAPPDATA");
-			if (envFolder == null || "".equals(envFolder)) {
-				return Path.of(System.getenv("USERPROFILE"), "AppData", "Local");
-			} else {
-				return Path.of(envFolder);
-			}
-		} else {
-			final String envFolder = System.getenv("XDG_CONFIG_HOME");
-			if (envFolder == null || "".equals(envFolder)) {
-				return Path.of(System.getenv("HOME"), ".config");
-			} else {
-				return Path.of(envFolder);
-			}
-		}
-	}
-
-	/** Gets a Path from a pathname in the config file. */
-	private static Path pathFromConfig(String pathname) {
-		return CONFIG_FILE.getParent().resolve(pathname);
-	}
-
+	
 	/**
 	 * Adds default units and dimensions to a database.
 	 * 
@@ -117,14 +94,28 @@ public final class Presenter {
 		// nonlinear units - must be loaded manually
 		database.addUnit("tempCelsius", Metric.CELSIUS);
 		database.addUnit("tempFahrenheit", BritishImperial.FAHRENHEIT);
-
+		
 		// load initial dimensions
 		database.addDimension("Length", Metric.Dimensions.LENGTH);
 		database.addDimension("Mass", Metric.Dimensions.MASS);
 		database.addDimension("Time", Metric.Dimensions.TIME);
 		database.addDimension("Temperature", Metric.Dimensions.TEMPERATURE);
 	}
-
+	
+	private static String displayRuleToString(
+			Function<UncertainDouble, String> numberDisplayRule) {
+		if (numberDisplayRule instanceof FixedDecimals)
+			return String.format("FIXED_DECIMALS %d",
+					((FixedDecimals) numberDisplayRule).decimalPlaces());
+		else if (numberDisplayRule instanceof FixedPrecision)
+			return String.format("FIXED_PRECISION %d",
+					((FixedPrecision) numberDisplayRule).significantFigures());
+		else if (numberDisplayRule instanceof UncertaintyBased)
+			return "UNCERTAINTY_BASED";
+		else
+			return numberDisplayRule.toString();
+	}
+	
 	/**
 	 * @return text in About file
 	 * @since 2022-02-19
@@ -134,7 +125,7 @@ public final class Presenter {
 				.map(Presenter::withoutComments).collect(Collectors.joining("\n"))
 				.replaceAll("\\[VERSION\\]", ProgramInfo.VERSION.toString());
 	}
-
+	
 	/**
 	 * Gets the text of a resource file as a set of strings (each one is one line
 	 * of the text).
@@ -145,7 +136,7 @@ public final class Presenter {
 	 */
 	private static final List<String> getLinesFromResource(String filename) {
 		final List<String> lines = new ArrayList<>();
-
+		
 		try (InputStream stream = inputStream(filename);
 				Scanner scanner = new Scanner(stream)) {
 			while (scanner.hasNextLine()) {
@@ -155,10 +146,10 @@ public final class Presenter {
 			throw new AssertionError(
 					"Error occurred while loading file " + filename, e);
 		}
-
+		
 		return lines;
 	}
-
+	
 	/**
 	 * Gets an input stream for a resource file.
 	 *
@@ -169,7 +160,38 @@ public final class Presenter {
 	private static final InputStream inputStream(String filepath) {
 		return Presenter.class.getResourceAsStream(filepath);
 	}
-
+	
+	private static Map.Entry<String, String> parseSettingLine(String line) {
+		final int equalsIndex = line.indexOf('=');
+		if (equalsIndex == -1)
+			throw new IllegalStateException(
+					"Settings file is malformed at line: " + line);
+		
+		final String param = line.substring(0, equalsIndex);
+		final String value = line.substring(equalsIndex + 1);
+		
+		return Map.entry(param, value);
+	}
+	
+	/** Gets a Path from a pathname in the config file. */
+	private static Path pathFromConfig(String pathname) {
+		return CONFIG_FILE.getParent().resolve(pathname);
+	}
+	
+	private static String searchRuleToString(
+			Function<Map.Entry<String, LinearUnit>, Map<String, LinearUnit>> searchRule) {
+		if (PrefixSearchRule.NO_PREFIXES.equals(searchRule))
+			return "NO_PREFIXES";
+		else if (PrefixSearchRule.COMMON_PREFIXES.equals(searchRule))
+			return "COMMON_PREFIXES";
+		else if (PrefixSearchRule.ALL_METRIC_PREFIXES.equals(searchRule))
+			return "ALL_METRIC_PREFIXES";
+		else
+			return searchRule.toString();
+	}
+	
+	// ====== SETTINGS ======
+	
 	/**
 	 * @return true iff a and b have any elements in common
 	 * @since 2022-04-19
@@ -181,7 +203,23 @@ public final class Presenter {
 		}
 		return false;
 	}
-
+	
+	private static final Path userConfigDir() {
+		if (System.getProperty("os.name").startsWith("Windows")) {
+			final String envFolder = System.getenv("LOCALAPPDATA");
+			if (envFolder == null || "".equals(envFolder))
+				return Path.of(System.getenv("USERPROFILE"), "AppData", "Local");
+			else
+				return Path.of(envFolder);
+		} else {
+			final String envFolder = System.getenv("XDG_CONFIG_HOME");
+			if (envFolder == null || "".equals(envFolder))
+				return Path.of(System.getenv("HOME"), ".config");
+			else
+				return Path.of(envFolder);
+		}
+	}
+	
 	/**
 	 * @return {@code line} with any comments removed.
 	 * @since 2021-03-13
@@ -190,25 +228,23 @@ public final class Presenter {
 		final int index = line.indexOf('#');
 		return index == -1 ? line : line.substring(0, index);
 	}
-
-	// ====== SETTINGS ======
-
+	
 	/**
 	 * The view that this presenter communicates with
 	 */
 	private final View view;
-
+	
 	/**
 	 * The database that this presenter communicates with (effectively the model)
 	 */
 	final UnitDatabase database;
-
+	
 	/**
 	 * The rule used for parsing input numbers. Any number-string inputted into
 	 * this program will be parsed using this method. <b>Not implemented yet.</b>
 	 */
 	private Function<String, UncertainDouble> numberParsingRule;
-
+	
 	/**
 	 * The rule used for displaying the results of unit conversions. The result
 	 * of unit conversions will be put into this function, and the resulting
@@ -216,41 +252,41 @@ public final class Presenter {
 	 */
 	private Function<UncertainDouble, String> numberDisplayRule = StandardDisplayRules
 			.uncertaintyBased();
-
+	
 	/**
 	 * A predicate that determines whether or not a certain combination of
 	 * prefixes is allowed. If it returns false, a combination of prefixes will
 	 * not be allowed. Prefixes are put in the list from right to left.
 	 */
 	private Predicate<List<UnitPrefix>> prefixRepetitionRule = DefaultPrefixRepetitionRule.NO_RESTRICTION;
-
+	
 	/**
 	 * A rule that accepts a prefixless name-unit pair and returns a map mapping
 	 * names to prefixed versions of that unit (including the unit itself) that
 	 * should be searchable.
 	 */
 	private Function<Map.Entry<String, LinearUnit>, Map<String, LinearUnit>> searchRule = PrefixSearchRule.NO_PREFIXES;
-
+	
 	/**
 	 * The set of units that is considered neither metric nor nonmetric for the
 	 * purposes of the metric-imperial one-way conversion. These units are
 	 * included in both From and To, even if One Way Conversion is enabled.
 	 */
 	private final Set<String> metricExceptions;
-
+	
 	/**
 	 * If this is true, views that show units as a list will have metric units
 	 * removed from the From unit list and imperial/USC units removed from the To
 	 * unit list.
 	 */
 	private boolean oneWayConversionEnabled = false;
-
+	
 	/**
 	 * If this is false, duplicate units and prefixes will be removed from the
 	 * unit view in views that show units as a list to choose from.
 	 */
 	private boolean showDuplicates = false;
-
+	
 	/**
 	 * Creates a Presenter
 	 * 
@@ -261,14 +297,14 @@ public final class Presenter {
 		this.view = view;
 		this.database = new UnitDatabase();
 		addDefaults(this.database);
-
+		
 		// load units and prefixes
 		try (final InputStream units = inputStream(DEFAULT_UNITS_FILEPATH)) {
 			this.database.loadUnitsFromStream(units);
 		} catch (final IOException e) {
 			throw new AssertionError("Loading of unitsfile.txt failed.", e);
 		}
-
+		
 		// load dimensions
 		try (final InputStream dimensions = inputStream(
 				DEFAULT_DIMENSIONS_FILEPATH)) {
@@ -276,7 +312,7 @@ public final class Presenter {
 		} catch (final IOException e) {
 			throw new AssertionError("Loading of dimensionfile.txt failed.", e);
 		}
-
+		
 		// load metric exceptions
 		try {
 			this.metricExceptions = new HashSet<>();
@@ -294,16 +330,16 @@ public final class Presenter {
 			throw new AssertionError("Loading of metric_exceptions.txt failed.",
 					e);
 		}
-
+		
 		// set default settings temporarily
 		if (Files.exists(CONFIG_FILE)) {
 			this.loadSettings(CONFIG_FILE);
 		}
-
+		
 		// a Predicate that returns true iff the argument is a full base unit
 		final Predicate<Unit> isFullBase = unit -> unit instanceof LinearUnit
 				&& ((LinearUnit) unit).isBase();
-
+		
 		// print out unit counts
 		System.out.printf(
 				"Successfully loaded %d units with %d unit names (%d base units).%n",
@@ -312,7 +348,7 @@ public final class Presenter {
 				this.database.unitMapPrefixless(false).values().stream()
 						.filter(isFullBase).count());
 	}
-
+	
 	/**
 	 * Applies a search rule to an entry in a name-unit map.
 	 *
@@ -332,7 +368,7 @@ public final class Presenter {
 		} else
 			return Stream.of(e);
 	}
-
+	
 	/**
 	 * Converts from the view's input expression to its output expression.
 	 * Displays an error message if any of the required fields are invalid.
@@ -346,10 +382,10 @@ public final class Presenter {
 	public void convertExpressions() {
 		if (this.view instanceof ExpressionConversionView) {
 			final ExpressionConversionView xcview = (ExpressionConversionView) this.view;
-
+			
 			final String fromExpression = xcview.getFromExpression();
 			final String toExpression = xcview.getToExpression();
-
+			
 			// expressions must not be empty
 			if (fromExpression.isEmpty()) {
 				this.view.showErrorMessage("Parse Error",
@@ -361,54 +397,131 @@ public final class Presenter {
 						"Please enter a unit expression in the To: box.");
 				return;
 			}
-
-			// evaluate expressions
-			final LinearUnitValue from;
-			final Unit to;
-			try {
-				from = this.database.evaluateUnitExpression(fromExpression);
-			} catch (final IllegalArgumentException | NoSuchElementException e) {
-				this.view.showErrorMessage("Parse Error",
-						"Could not recognize text in From entry: " + e.getMessage());
-				return;
+			
+			final Optional<UnitConversionRecord> uc;
+			if (toExpression.contains(";")) {
+				final String[] toExpressions = toExpression.split(";");
+				uc = this.convertExpressionToMultiUnit(fromExpression,
+						toExpressions);
+			} else {
+				uc = this.convertExpressionToExpression(fromExpression,
+						toExpression);
+			}
+			
+			uc.ifPresent(xcview::showExpressionConversionOutput);
+		} else
+			throw new UnsupportedOperationException(
+					"This function can only be called when the view is an ExpressionConversionView");
+	}
+	
+	/**
+	 * Converts a unit expression to another expression.
+	 * 
+	 * If an error happened, it is shown to the view and Optional.empty() is
+	 * returned.
+	 * 
+	 * @since 2024-08-15
+	 */
+	private Optional<UnitConversionRecord> convertExpressionToExpression(
+			String fromExpression, String toExpression) {
+		// evaluate expressions
+		final LinearUnitValue from;
+		final Unit to;
+		try {
+			from = this.database.evaluateUnitExpression(fromExpression);
+		} catch (final IllegalArgumentException | NoSuchElementException e) {
+			this.view.showErrorMessage("Parse Error",
+					"Could not recognize text in From entry: " + e.getMessage());
+			return Optional.empty();
+		}
+		try {
+			to = this.database.getUnitFromExpression(toExpression);
+		} catch (final IllegalArgumentException | NoSuchElementException e) {
+			this.view.showErrorMessage("Parse Error",
+					"Could not recognize text in To entry: " + e.getMessage());
+			return Optional.empty();
+		}
+		
+		// convert and show output
+		if (from.getUnit().canConvertTo(to)) {
+			final UncertainDouble uncertainValue;
+			
+			// uncertainty is meaningless for non-linear units, so we will have
+			// to erase uncertainty information for them
+			if (to instanceof LinearUnit) {
+				final var toLinear = (LinearUnit) to;
+				uncertainValue = from.convertTo(toLinear).getValue();
+			} else {
+				final double value = from.asUnitValue().convertTo(to).getValue();
+				uncertainValue = UncertainDouble.of(value, 0);
 			}
+			
+			final UnitConversionRecord uc = UnitConversionRecord.valueOf(
+					fromExpression, toExpression, "",
+					this.numberDisplayRule.apply(uncertainValue));
+			return Optional.of(uc);
+		} else {
+			this.view.showErrorMessage("Conversion Error",
+					"Cannot convert between \"" + fromExpression + "\" and \""
+							+ toExpression + "\".");
+			return Optional.empty();
+		}
+		
+	}
+	
+	/**
+	 * Convert an expression to a MultiUnit. If an error happened, it is shown to
+	 * the view and Optional.empty() is returned.
+	 *
+	 * @since 2024-08-15
+	 */
+	private Optional<UnitConversionRecord> convertExpressionToMultiUnit(
+			String fromExpression, String[] toExpressions) {
+		final LinearUnitValue from;
+		try {
+			from = this.database.evaluateUnitExpression(fromExpression);
+		} catch (final IllegalArgumentException | NoSuchElementException e) {
+			this.view.showErrorMessage("Parse Error",
+					"Could not recognize text in From entry: " + e.getMessage());
+			return Optional.empty();
+		}
+		
+		final List<LinearUnit> toUnits = new ArrayList<>(toExpressions.length);
+		for (int i = 0; i < toExpressions.length; i++) {
 			try {
-				to = this.database.getUnitFromExpression(toExpression);
+				final Unit toI = this.database
+						.getUnitFromExpression(toExpressions[i].trim());
+				if (toI instanceof LinearUnit) {
+					toUnits.add((LinearUnit) toI);
+				} else {
+					this.view.showErrorMessage("Unit Type Error",
+							"Units separated by ';' must be linear; " + toI
+									+ " is not.");
+					return Optional.empty();
+				}
 			} catch (final IllegalArgumentException | NoSuchElementException e) {
 				this.view.showErrorMessage("Parse Error",
 						"Could not recognize text in To entry: " + e.getMessage());
-				return;
-			}
-
-			// convert and show output
-			if (from.getUnit().canConvertTo(to)) {
-				final UncertainDouble uncertainValue;
-
-				// uncertainty is meaningless for non-linear units, so we will have
-				// to erase uncertainty information for them
-				if (to instanceof LinearUnit) {
-					final var toLinear = (LinearUnit) to;
-					uncertainValue = from.convertTo(toLinear).getValue();
-				} else {
-					final double value = from.asUnitValue().convertTo(to).getValue();
-					uncertainValue = UncertainDouble.of(value, 0);
-				}
-
-				final UnitConversionRecord uc = UnitConversionRecord.valueOf(
-						fromExpression, toExpression, "",
-						this.numberDisplayRule.apply(uncertainValue));
-				xcview.showExpressionConversionOutput(uc);
-			} else {
-				this.view.showErrorMessage("Conversion Error",
-						"Cannot convert between \"" + fromExpression + "\" and \""
-								+ toExpression + "\".");
+				return Optional.empty();
 			}
-
-		} else
-			throw new UnsupportedOperationException(
-					"This function can only be called when the view is an ExpressionConversionView");
+		}
+		
+		final List<LinearUnitValue> toValues;
+		try {
+			toValues = from.convertToMultiple(toUnits);
+		} catch (final IllegalArgumentException e) {
+			this.view.showErrorMessage("Unit Error",
+					"Invalid units separated by ';': " + e.getMessage());
+			return Optional.empty();
+		}
+		
+		final String toExpression = toValues.stream().map(
+				v -> this.numberDisplayRule.apply(v.getValue()) + " " + v.getUnit())
+				.collect(Collectors.joining(" + "));
+		return Optional.of(
+				UnitConversionRecord.valueOf(fromExpression, toExpression, "", ""));
 	}
-
+	
 	/**
 	 * Converts from the view's input unit to its output unit. Displays an error
 	 * message if any of the required fields are invalid.
@@ -422,11 +535,11 @@ public final class Presenter {
 	public void convertUnits() {
 		if (this.view instanceof UnitConversionView) {
 			final UnitConversionView ucview = (UnitConversionView) this.view;
-
+			
 			final Optional<String> fromUnitOptional = ucview.getFromSelection();
 			final Optional<String> toUnitOptional = ucview.getToSelection();
 			final String inputValueString = ucview.getInputValue();
-
+			
 			// extract values from optionals
 			final String fromUnitString, toUnitString;
 			if (fromUnitOptional.isPresent()) {
@@ -443,11 +556,11 @@ public final class Presenter {
 						"Please specify a To unit");
 				return;
 			}
-
+			
 			// convert strings to data, checking if anything is invalid
 			final Unit fromUnit, toUnit;
 			final UncertainDouble uncertainValue;
-
+			
 			if (this.database.containsUnitName(fromUnitString)) {
 				fromUnit = this.database.getUnit(fromUnitString);
 			} else
@@ -464,11 +577,11 @@ public final class Presenter {
 						"Invalid value " + inputValueString);
 				return;
 			}
-
+			
 			if (!fromUnit.canConvertTo(toUnit))
 				throw this.viewError("Could not convert between %s and %s",
 						fromUnit, toUnit);
-
+				
 			// convert - we will need to erase uncertainty for non-linear units, so
 			// we need to treat linear and non-linear units differently
 			final String outputValueString;
@@ -478,18 +591,18 @@ public final class Presenter {
 				final LinearUnitValue initialValue = LinearUnitValue.of(fromLinear,
 						uncertainValue);
 				final LinearUnitValue converted = initialValue.convertTo(toLinear);
-
+				
 				outputValueString = this.numberDisplayRule
 						.apply(converted.getValue());
 			} else {
 				final UnitValue initialValue = UnitValue.of(fromUnit,
 						uncertainValue.value());
 				final UnitValue converted = initialValue.convertTo(toUnit);
-
+				
 				outputValueString = this.numberDisplayRule
 						.apply(UncertainDouble.of(converted.getValue(), 0));
 			}
-
+			
 			ucview.showUnitConversionOutput(
 					UnitConversionRecord.valueOf(fromUnitString, toUnitString,
 							inputValueString, outputValueString));
@@ -497,7 +610,7 @@ public final class Presenter {
 			throw new UnsupportedOperationException(
 					"This function can only be called when the view is a UnitConversionView.");
 	}
-
+	
 	/**
 	 * @return true iff duplicate units are shown in unit lists
 	 * @since 2022-03-30
@@ -505,7 +618,7 @@ public final class Presenter {
 	public boolean duplicatesShown() {
 		return this.showDuplicates;
 	}
-
+	
 	/**
 	 * Gets a name for this dimension using the database
 	 *
@@ -520,7 +633,7 @@ public final class Presenter {
 				.filter(d -> d.equals(dimension)).findAny().map(Nameable::getName)
 				.orElse(dimension.toString(Nameable::getName));
 	}
-
+	
 	/**
 	 * @return the rule that is used by this presenter to convert numbers into
 	 *         strings
@@ -529,7 +642,7 @@ public final class Presenter {
 	public Function<UncertainDouble, String> getNumberDisplayRule() {
 		return this.numberDisplayRule;
 	}
-
+	
 	/**
 	 * @return the rule that is used by this presenter to convert strings into
 	 *         numbers
@@ -539,7 +652,7 @@ public final class Presenter {
 	private Function<String, UncertainDouble> getNumberParsingRule() {
 		return this.numberParsingRule;
 	}
-
+	
 	/**
 	 * @return the rule that determines whether a set of prefixes is valid
 	 * @since 2022-04-19
@@ -547,7 +660,7 @@ public final class Presenter {
 	public Predicate<List<UnitPrefix>> getPrefixRepetitionRule() {
 		return this.prefixRepetitionRule;
 	}
-
+	
 	/**
 	 * @return the rule that determines which units are prefixed
 	 * @since 2022-07-08
@@ -555,7 +668,7 @@ public final class Presenter {
 	public Function<Map.Entry<String, LinearUnit>, Map<String, LinearUnit>> getSearchRule() {
 		return this.searchRule;
 	}
-
+	
 	/**
 	 * @return a search rule that shows all single prefixes
 	 * @since 2022-07-08
@@ -564,7 +677,7 @@ public final class Presenter {
 		return PrefixSearchRule.getCoherentOnlyRule(
 				new HashSet<>(this.database.prefixMap(true).values()));
 	}
-
+	
 	/**
 	 * @return the view associated with this presenter
 	 * @since 2022-04-19
@@ -572,7 +685,7 @@ public final class Presenter {
 	public View getView() {
 		return this.view;
 	}
-
+	
 	/**
 	 * @return whether or not the provided unit is semi-metric (i.e. an
 	 *         exception)
@@ -588,7 +701,18 @@ public final class Presenter {
 						&& this.metricExceptions.contains(symbol.orElseThrow())
 				|| sharesAnyElements(this.metricExceptions, u.getOtherNames());
 	}
-
+	
+	private void loadExceptionFile(Path exceptionFile) {
+		try (Stream<String> lines = Files.lines(exceptionFile)) {
+			lines.map(Presenter::withoutComments)
+					.forEach(this.metricExceptions::add);
+		} catch (final IOException e) {
+			this.view.showErrorMessage("File Load Error",
+					"Error loading configured metric exception file \""
+							+ exceptionFile + "\": " + e.getLocalizedMessage());
+		}
+	}
+	
 	/**
 	 * Loads settings from the user's settings file and applies them to the
 	 * presenter.
@@ -597,9 +721,10 @@ public final class Presenter {
 	 * @since 2021-12-15
 	 */
 	void loadSettings(Path settingsFile) {
-		for (Map.Entry<String, String> setting : settingsFromFile(settingsFile)) {
+		for (final Map.Entry<String, String> setting : this
+				.settingsFromFile(settingsFile)) {
 			final String value = setting.getValue();
-
+			
 			switch (setting.getKey()) {
 			// set manually to avoid the unnecessary saving of the non-manual
 			// methods
@@ -635,86 +760,12 @@ public final class Presenter {
 				break;
 			}
 		}
-
+		
 		if (this.view.getPresenter() != null) {
 			this.updateView();
 		}
 	}
-
-	private List<Map.Entry<String, String>> settingsFromFile(Path settingsFile) {
-		try (Stream<String> lines = Files.lines(settingsFile)) {
-			return lines.map(Presenter::withoutComments)
-					.filter(line -> !line.isBlank()).map(Presenter::parseSettingLine)
-					.toList();
-		} catch (final IOException e) {
-			this.view.showErrorMessage("Settings Loading Error",
-					"Error loading settings file.  Using default settings.");
-			return null;
-		}
-	}
-
-	private static Map.Entry<String, String> parseSettingLine(String line) {
-		final int equalsIndex = line.indexOf('=');
-		if (equalsIndex == -1)
-			throw new IllegalStateException(
-					"Settings file is malformed at line: " + line);
-
-		final String param = line.substring(0, equalsIndex);
-		final String value = line.substring(equalsIndex + 1);
-
-		return Map.entry(param, value);
-	}
-
-	private void setSearchRuleFromString(String ruleString) {
-		switch (ruleString) {
-		case "NO_PREFIXES":
-			this.searchRule = PrefixSearchRule.NO_PREFIXES;
-			break;
-		case "COMMON_PREFIXES":
-			this.searchRule = PrefixSearchRule.COMMON_PREFIXES;
-			break;
-		case "ALL_METRIC_PREFIXES":
-			this.searchRule = PrefixSearchRule.ALL_METRIC_PREFIXES;
-			break;
-		default:
-			System.err.printf(
-					"Warning: unrecognized value for search_prefix_rule: %s\n",
-					ruleString);
-		}
-	}
-
-	private void setDisplayRuleFromString(String ruleString) {
-		String[] tokens = ruleString.split(" ");
-		switch (tokens[0]) {
-		case "FIXED_DECIMALS":
-			final int decimals = Integer.parseInt(tokens[1]);
-			this.numberDisplayRule = StandardDisplayRules.fixedDecimals(decimals);
-			break;
-		case "FIXED_PRECISION":
-			final int sigDigs = Integer.parseInt(tokens[1]);
-			this.numberDisplayRule = StandardDisplayRules.fixedPrecision(sigDigs);
-			break;
-		case "UNCERTAINTY_BASED":
-			this.numberDisplayRule = StandardDisplayRules.uncertaintyBased();
-			break;
-		default:
-			this.numberDisplayRule = StandardDisplayRules
-					.getStandardRule(ruleString);
-			break;
-		}
-	}
-
-	private void loadExceptionFile(Path exceptionFile) {
-		try (Stream<String> lines = Files.lines(exceptionFile)) {
-			lines.map(Presenter::withoutComments)
-					.forEach(this.metricExceptions::add);
-		} catch (IOException e) {
-			this.view.showErrorMessage("File Load Error",
-					"Error loading configured metric exception file \""
-							+ exceptionFile + "\": " + e.getLocalizedMessage());
-		}
-	}
-
+	
 	/**
 	 * @return true iff the One-Way Conversion feature is available (views that
 	 *         show units as a list will have metric units removed from the From
@@ -725,7 +776,7 @@ public final class Presenter {
 	public boolean oneWayConversionEnabled() {
 		return this.oneWayConversionEnabled;
 	}
-
+	
 	/**
 	 * Completes creation of the presenter. This part of the initialization
 	 * depends on the view's functions, so it cannot be run if the components
@@ -739,10 +790,10 @@ public final class Presenter {
 			final UnitConversionView ucview = (UnitConversionView) this.view;
 			ucview.setDimensionNames(this.database.dimensionMap().keySet());
 		}
-
+		
 		this.updateView();
 	}
-
+	
 	void prefixSelected() {
 		final Optional<String> selectedPrefixName = this.view
 				.getViewedPrefixName();
@@ -754,7 +805,7 @@ public final class Presenter {
 				.ifPresent(prefix -> this.view.showPrefix(prefix.getNameSymbol(),
 						String.valueOf(prefix.getMultiplier())));
 	}
-
+	
 	/**
 	 * Saves the presenter's current settings to the config file, creating it if
 	 * it doesn't exist.
@@ -767,68 +818,35 @@ public final class Presenter {
 		if (!Files.exists(configDir)) {
 			try {
 				Files.createDirectories(configDir);
-			} catch (IOException e) {
+			} catch (final IOException e) {
 				return false;
 			}
 		}
-
+		
 		return this.writeSettings(CONFIG_FILE);
 	}
-
-	/**
-	 * Saves the presenter's settings to the user settings file.
-	 * 
-	 * @param settingsFile file settings should be saved to
-	 * @since 2021-12-15
-	 */
-	boolean writeSettings(Path settingsFile) {
-		try (BufferedWriter writer = Files.newBufferedWriter(settingsFile)) {
-			writer.write(String.format("number_display_rule=%s\n",
-					displayRuleToString(this.numberDisplayRule)));
-			writer.write(
-					String.format("prefix_rule=%s\n", this.prefixRepetitionRule));
-			writer.write(
-					String.format("one_way=%s\n", this.oneWayConversionEnabled));
-			writer.write(
-					String.format("include_duplicates=%s\n", this.showDuplicates));
-			writer.write(String.format("search_prefix_rule=%s\n",
-					searchRuleToString(this.searchRule)));
-			return true;
-		} catch (final IOException e) {
-			e.printStackTrace();
-			this.view.showErrorMessage("I/O Error",
-					"Error occurred while saving settings: "
-							+ e.getLocalizedMessage());
-			return false;
+	
+	private void setDisplayRuleFromString(String ruleString) {
+		final String[] tokens = ruleString.split(" ");
+		switch (tokens[0]) {
+		case "FIXED_DECIMALS":
+			final int decimals = Integer.parseInt(tokens[1]);
+			this.numberDisplayRule = StandardDisplayRules.fixedDecimals(decimals);
+			break;
+		case "FIXED_PRECISION":
+			final int sigDigs = Integer.parseInt(tokens[1]);
+			this.numberDisplayRule = StandardDisplayRules.fixedPrecision(sigDigs);
+			break;
+		case "UNCERTAINTY_BASED":
+			this.numberDisplayRule = StandardDisplayRules.uncertaintyBased();
+			break;
+		default:
+			this.numberDisplayRule = StandardDisplayRules
+					.getStandardRule(ruleString);
+			break;
 		}
 	}
-
-	private static String searchRuleToString(
-			Function<Map.Entry<String, LinearUnit>, Map<String, LinearUnit>> searchRule) {
-		if (PrefixSearchRule.NO_PREFIXES.equals(searchRule)) {
-			return "NO_PREFIXES";
-		} else if (PrefixSearchRule.COMMON_PREFIXES.equals(searchRule)) {
-			return "COMMON_PREFIXES";
-		} else if (PrefixSearchRule.ALL_METRIC_PREFIXES.equals(searchRule)) {
-			return "ALL_METRIC_PREFIXES";
-		} else
-			return searchRule.toString();
-	}
-
-	private static String displayRuleToString(
-			Function<UncertainDouble, String> numberDisplayRule) {
-		if (numberDisplayRule instanceof FixedDecimals) {
-			return String.format("FIXED_DECIMALS %d",
-					((FixedDecimals) numberDisplayRule).decimalPlaces());
-		} else if (numberDisplayRule instanceof FixedPrecision) {
-			return String.format("FIXED_PRECISION %d",
-					((FixedPrecision) numberDisplayRule).significantFigures());
-		} else if (numberDisplayRule instanceof UncertaintyBased) {
-			return "UNCERTAINTY_BASED";
-		} else
-			return numberDisplayRule.toString();
-	}
-
+	
 	/**
 	 * @param numberDisplayRule the new rule that will be used by this presenter
 	 *                          to convert numbers into strings
@@ -838,7 +856,7 @@ public final class Presenter {
 			Function<UncertainDouble, String> numberDisplayRule) {
 		this.numberDisplayRule = numberDisplayRule;
 	}
-
+	
 	/**
 	 * @param numberParsingRule the new rule that will be used by this presenter
 	 *                          to convert strings into numbers
@@ -849,7 +867,7 @@ public final class Presenter {
 			Function<String, UncertainDouble> numberParsingRule) {
 		this.numberParsingRule = numberParsingRule;
 	}
-
+	
 	/**
 	 * @param oneWayConversionEnabled whether not one-way conversion should be
 	 *                                enabled
@@ -860,7 +878,7 @@ public final class Presenter {
 		this.oneWayConversionEnabled = oneWayConversionEnabled;
 		this.updateView();
 	}
-
+	
 	/**
 	 * @param prefixRepetitionRule the rule that determines whether a set of
 	 *                             prefixes is valid
@@ -871,7 +889,7 @@ public final class Presenter {
 		this.prefixRepetitionRule = prefixRepetitionRule;
 		this.database.setPrefixRepetitionRule(prefixRepetitionRule);
 	}
-
+	
 	/**
 	 * @param searchRule A rule that accepts a prefixless name-unit pair and
 	 *                   returns a map mapping names to prefixed versions of that
@@ -883,7 +901,25 @@ public final class Presenter {
 			Function<Map.Entry<String, LinearUnit>, Map<String, LinearUnit>> searchRule) {
 		this.searchRule = searchRule;
 	}
-
+	
+	private void setSearchRuleFromString(String ruleString) {
+		switch (ruleString) {
+		case "NO_PREFIXES":
+			this.searchRule = PrefixSearchRule.NO_PREFIXES;
+			break;
+		case "COMMON_PREFIXES":
+			this.searchRule = PrefixSearchRule.COMMON_PREFIXES;
+			break;
+		case "ALL_METRIC_PREFIXES":
+			this.searchRule = PrefixSearchRule.ALL_METRIC_PREFIXES;
+			break;
+		default:
+			System.err.printf(
+					"Warning: unrecognized value for search_prefix_rule: %s\n",
+					ruleString);
+		}
+	}
+	
 	/**
 	 * @param showDuplicateUnits whether or not duplicate units should be shown
 	 * @since 2022-03-30
@@ -892,7 +928,19 @@ public final class Presenter {
 		this.showDuplicates = showDuplicateUnits;
 		this.updateView();
 	}
-
+	
+	private List<Map.Entry<String, String>> settingsFromFile(Path settingsFile) {
+		try (Stream<String> lines = Files.lines(settingsFile)) {
+			return lines.map(Presenter::withoutComments)
+					.filter(line -> !line.isBlank()).map(Presenter::parseSettingLine)
+					.toList();
+		} catch (final IOException e) {
+			this.view.showErrorMessage("Settings Loading Error",
+					"Error loading settings file.  Using default settings.");
+			return null;
+		}
+	}
+	
 	/**
 	 * Shows a unit in the unit viewer
 	 *
@@ -908,7 +956,7 @@ public final class Presenter {
 		final var unitType = UnitType.getType(u, this::isSemiMetric);
 		this.view.showUnit(nameSymbol, definition, dimensionString, unitType);
 	}
-
+	
 	/**
 	 * Runs whenever a unit name is selected in the unit viewer. Gets the
 	 * description of a unit and displays it.
@@ -924,7 +972,7 @@ public final class Presenter {
 						: null);
 		selectedUnit.ifPresent(this::showUnit);
 	}
-
+	
 	/**
 	 * Updates the view's From and To units, if it has some
 	 * 
@@ -934,19 +982,19 @@ public final class Presenter {
 		if (this.view instanceof UnitConversionView) {
 			final UnitConversionView ucview = (UnitConversionView) this.view;
 			final var selectedDimensionName = ucview.getSelectedDimensionName();
-
+			
 			// load units & prefixes into viewers
 			this.view.setViewableUnitNames(
 					this.database.unitMapPrefixless(this.showDuplicates).keySet());
 			this.view.setViewablePrefixNames(
 					this.database.prefixMap(this.showDuplicates).keySet());
-
+			
 			// get From and To units
 			var fromUnits = this.database.unitMapPrefixless(this.showDuplicates)
 					.entrySet().stream();
 			var toUnits = this.database.unitMapPrefixless(this.showDuplicates)
 					.entrySet().stream();
-
+			
 			// filter by dimension, if one is selected
 			if (selectedDimensionName.isPresent()) {
 				final var viewDimension = this.database
@@ -956,7 +1004,7 @@ public final class Presenter {
 				toUnits = toUnits.filter(
 						u -> viewDimension.equals(u.getValue().getDimension()));
 			}
-
+			
 			// filter by unit type, if desired
 			if (this.oneWayConversionEnabled) {
 				fromUnits = fromUnits.filter(u -> UnitType.getType(u.getValue(),
@@ -964,7 +1012,7 @@ public final class Presenter {
 				toUnits = toUnits.filter(u -> UnitType.getType(u.getValue(),
 						this::isSemiMetric) != UnitType.NON_METRIC);
 			}
-
+			
 			// set unit names
 			ucview.setFromUnitNames(fromUnits.flatMap(this::applySearchRule)
 					.map(Map.Entry::getKey).collect(Collectors.toSet()));
@@ -972,7 +1020,7 @@ public final class Presenter {
 					.map(Map.Entry::getKey).collect(Collectors.toSet()));
 		}
 	}
-
+	
 	/**
 	 * @param message message to add
 	 * @param args    string formatting arguments for message
@@ -984,4 +1032,32 @@ public final class Presenter {
 		return new AssertionError("View Programming Error (from " + this.view
 				+ "): " + String.format(message, args));
 	}
+	
+	/**
+	 * Saves the presenter's settings to the user settings file.
+	 * 
+	 * @param settingsFile file settings should be saved to
+	 * @since 2021-12-15
+	 */
+	boolean writeSettings(Path settingsFile) {
+		try (BufferedWriter writer = Files.newBufferedWriter(settingsFile)) {
+			writer.write(String.format("number_display_rule=%s\n",
+					displayRuleToString(this.numberDisplayRule)));
+			writer.write(
+					String.format("prefix_rule=%s\n", this.prefixRepetitionRule));
+			writer.write(
+					String.format("one_way=%s\n", this.oneWayConversionEnabled));
+			writer.write(
+					String.format("include_duplicates=%s\n", this.showDuplicates));
+			writer.write(String.format("search_prefix_rule=%s\n",
+					searchRuleToString(this.searchRule)));
+			return true;
+		} catch (final IOException e) {
+			e.printStackTrace();
+			this.view.showErrorMessage("I/O Error",
+					"Error occurred while saving settings: "
+							+ e.getLocalizedMessage());
+			return false;
+		}
+	}
 }