From ec036fdad931fbbd7dec28b864150f8668e91b41 Mon Sep 17 00:00:00 2001
From: Adrien Hopkins <adrien.p.hopkins@gmail.com>
Date: Wed, 10 Apr 2019 21:00:49 -0400
Subject: Edited dimension database code and improved comments.

getDimension() now works with exponents,
Added a dimension parser,
comments can now be in the middle of lines
---
 CHANGELOG.org                            |   1 +
 src/org/unitConverter/UnitsDatabase.java | 181 +++++++++++++++++++------------
 2 files changed, 115 insertions(+), 67 deletions(-)

diff --git a/CHANGELOG.org b/CHANGELOG.org
index 95dc57a..8a79c46 100644
--- a/CHANGELOG.org
+++ b/CHANGELOG.org
@@ -6,6 +6,7 @@ All notable changes in this project will be shown in this file.
  - Moved project to Maven
  - Downgraded JUnit to 4.11
  - BaseUnit is now a subclass of LinearUnit
+ - Comments can now start in the middle of lines
 *** Added
  - GUI for a selection-based unit converter
  - The UnitDatabase now stores dimensions.
diff --git a/src/org/unitConverter/UnitsDatabase.java b/src/org/unitConverter/UnitsDatabase.java
index 290a425..69b25d8 100755
--- a/src/org/unitConverter/UnitsDatabase.java
+++ b/src/org/unitConverter/UnitsDatabase.java
@@ -48,6 +48,32 @@ import org.unitConverter.unit.UnitPrefix;
  * @since v0.1.0
  */
 public final class UnitsDatabase {
+	/**
+	 * The exponent operator
+	 * 
+	 * @param base
+	 *            base of exponentiation
+	 * @param exponentUnit
+	 *            exponent
+	 * @return result
+	 * @since 2019-04-10
+	 */
+	private static final LinearUnit exponent(final LinearUnit base, final LinearUnit exponentUnit) {
+		// exponent function - first check if o2 is a number,
+		if (exponentUnit.getBase().equals(SI.SI.getBaseUnit(UnitDimension.EMPTY))) {
+			// then check if it is an integer,
+			final double exponent = exponentUnit.getConversionFactor();
+			if (DecimalComparison.equals(exponent % 1, 0))
+				// then exponentiate
+				return base.toExponent((int) (exponent % 1 + 0.5));
+			else
+				// not an integer
+				throw new UnsupportedOperationException("Decimal exponents are currently not supported.");
+		} else
+			// not a number
+			throw new IllegalArgumentException("Exponents must be numbers.");
+	}
+
 	/**
 	 * The units in this system.
 	 * 
@@ -80,22 +106,12 @@ public final class UnitsDatabase {
 			this::getLinearUnit).addBinaryOperator("+", (o1, o2) -> o1.plus(o2), 0)
 					.addBinaryOperator("-", (o1, o2) -> o1.minus(o2), 0)
 					.addBinaryOperator("*", (o1, o2) -> o1.times(o2), 1).addSpaceFunction("*")
-					.addBinaryOperator("/", (o1, o2) -> o1.dividedBy(o2), 1).addBinaryOperator("^", (o1, o2) -> {
-						// exponent function - first check if o2 is a number,
-						if (o2.getBase().equals(SI.SI.getBaseUnit(UnitDimension.EMPTY))) {
-							// then check if it is an integer,
-							final double exponent = o2.getConversionFactor();
-							if (DecimalComparison.equals(exponent % 1, 0))
-								// then exponentiate
-								return o1.toExponent((int) (exponent % 1 + 0.5));
-							else
-								// not an integer
-								throw new UnsupportedOperationException(
-										"Decimal exponents are currently not supported.");
-						} else
-							// not a number
-							throw new IllegalArgumentException("Exponents must be numbers.");
-					}, 2).build();
+					.addBinaryOperator("/", (o1, o2) -> o1.dividedBy(o2), 1)
+					.addBinaryOperator("^", UnitsDatabase::exponent, 2).build();
+
+	private final ExpressionParser<UnitDimension> unitDimensionParser = new ExpressionParser.Builder<>(
+			this::getDimension).addBinaryOperator("*", (o1, o2) -> o1.times(o2), 0).addSpaceFunction("*")
+					.addBinaryOperator("/", (o1, o2) -> o1.dividedBy(o2), 0).build();
 
 	/**
 	 * Creates the {@code UnitsDatabase}.
@@ -118,7 +134,7 @@ public final class UnitsDatabase {
 	 * <p>
 	 * Allowed exceptions:
 	 * <ul>
-	 * <li>Any line that begins with the '#' character is considered a comment and ignored.</li>
+	 * <li>Anything after a '#' character is considered a comment and ignored.</li>
 	 * <li>Blank lines are also ignored</li>
 	 * <li>If an expression consists of a single exclamation point, instead of parsing it, this method will search the
 	 * database for an existing unit. If no unit is found, an IllegalArgumentException is thrown. This is used to define
@@ -140,56 +156,7 @@ public final class UnitsDatabase {
 			// while the reader has lines to read, read a line, then parse it, then add it
 			long lineCounter = 0;
 			while (reader.ready()) {
-				final String line = reader.readLine();
-				lineCounter++;
-
-				// ignore lines that start with a # sign - they're comments
-				if (line.startsWith("#") || line.isEmpty()) {
-					continue;
-				}
-
-				// divide line into name and expression
-				final String[] parts = line.split("\t");
-				if (parts.length < 2)
-					throw new IllegalArgumentException(String.format(
-							"Lines must consist of a unit name and its definition, separated by tab(s) (line %d).",
-							lineCounter));
-				final String name = parts[0];
-				final String expression = parts[parts.length - 1];
-
-				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
-				if (expression.equals("!")) {
-					if (!this.containsUnitName(name))
-						throw new IllegalArgumentException(
-								String.format("! used but no unit found (line %d).", lineCounter));
-				} else {
-					if (name.endsWith("-")) {
-						final UnitPrefix prefix;
-						try {
-							prefix = this.getPrefixFromExpression(expression);
-						} catch (final IllegalArgumentException e) {
-							System.err.printf("Parsing error on line %d:%n", lineCounter);
-							throw e;
-						}
-						this.addPrefix(name.substring(0, name.length() - 1), prefix);
-					} else {
-						// it's a unit, get the unit
-						final Unit unit;
-						try {
-							unit = this.getUnitFromExpression(expression);
-						} catch (final IllegalArgumentException e) {
-							System.err.printf("Parsing error on line %d:%n", lineCounter);
-							throw e;
-						}
-
-						this.addUnit(name, unit);
-					}
-				}
+				this.addFromLine(reader.readLine(), ++lineCounter);
 			}
 		} catch (final FileNotFoundException e) {
 			throw new IllegalArgumentException("Could not find file " + file, e);
@@ -214,6 +181,67 @@ public final class UnitsDatabase {
 				Objects.requireNonNull(dimension, "dimension must not be null."));
 	}
 
+	/**
+	 * Adds to the list from a line in a unit file.
+	 * 
+	 * @param line
+	 *            line to look at
+	 * @param lineCounter
+	 *            number of line, for error messages
+	 * @since 2019-04-10
+	 */
+	private void addFromLine(final String line, final long lineCounter) {
+		// ignore lines that start with a # sign - they're comments
+		if (line.isEmpty())
+			return;
+		if (line.contains("#")) {
+			this.addFromLine(line.substring(0, line.indexOf("#")), lineCounter);
+			return;
+		}
+
+		// divide line into name and expression
+		final String[] parts = line.split("\t");
+		if (parts.length < 2)
+			throw new IllegalArgumentException(String.format(
+					"Lines must consist of a unit name and its definition, separated by tab(s) (line %d).",
+					lineCounter));
+		final String name = parts[0];
+		final String expression = parts[parts.length - 1];
+
+		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
+		if (expression.equals("!")) {
+			if (!this.containsUnitName(name))
+				throw new IllegalArgumentException(String.format("! used but no unit found (line %d).", lineCounter));
+		} else {
+			if (name.endsWith("-")) {
+				final UnitPrefix prefix;
+				try {
+					prefix = this.getPrefixFromExpression(expression);
+				} catch (final IllegalArgumentException e) {
+					System.err.printf("Parsing error on line %d:%n", lineCounter);
+					throw e;
+				}
+				this.addPrefix(name.substring(0, name.length() - 1), prefix);
+			} else {
+				// it's a unit, get the unit
+				final Unit unit;
+				try {
+					unit = this.getUnitFromExpression(expression);
+				} catch (final IllegalArgumentException e) {
+					System.err.printf("Parsing error on line %d:%n", lineCounter);
+					throw e;
+				}
+
+				this.addUnit(name, unit);
+			}
+		}
+	}
+
 	/**
 	 * Adds a unit prefix to the database.
 	 * 
@@ -316,12 +344,31 @@ public final class UnitsDatabase {
 	/**
 	 * Gets a unit dimension from the database using its name.
 	 * 
+	 * <p>
+	 * This method accepts exponents, like "L^3"
+	 * </p>
+	 * 
 	 * @param name
 	 *            dimension's name
 	 * @return dimension
 	 * @since 2019-03-14
 	 */
 	public UnitDimension getDimension(final String name) {
+		Objects.requireNonNull(name, "name must not be null.");
+		if (name.contains("^")) {
+			final String[] baseAndExponent = name.split("\\^");
+
+			final UnitDimension base = this.getDimension(baseAndExponent[0]);
+
+			final int exponent;
+			try {
+				exponent = Integer.parseInt(baseAndExponent[baseAndExponent.length - 1]);
+			} catch (final NumberFormatException e2) {
+				throw new IllegalArgumentException("Exponent must be an integer.");
+			}
+
+			return base.toExponent(exponent);
+		}
 		return this.dimensions.get(name);
 	}
 
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