Bug fixes with fractions

- Entering negative fractions would calculate incorrectly
- Fraction rounding didn't work correctly
- Updated and added tests for fractions
- When rounding, allow for a precions of 0 (no decimals)
- Created a spreadsheet to help with fraction testing
- Removed the silly '0/1' in the fraction display

pom.xml

@@ -3,7 +3,7 @@
 
 	<groupId>org.fross</groupId>
 	<artifactId>rpncalc</artifactId>
-	<version>5.0.14</version>
+	<version>5.1.0</version>
 	<packaging>jar</packaging>
 
 	<name>rpncalc</name>

snap/snapcraft.yaml

@@ -1,5 +1,5 @@
 name: rpncalc
-version: '5.0.14'
+version: '5.1.0'
 summary: The command line Reverse Polish Notation (RPN) calculator
 description: |
   RPNCalc is an easy to use command line based Reverse Polish

src/main/java/org/fross/rpncalc/CommandParser.java

@@ -206,6 +206,7 @@ public static void Parse(StackObj calcStack, StackObj calcStack2, String cmdInpu
 		case "frac":
 		case "fraction":
 			String[] outString = StackConversions.cmdFraction(calcStack, cmdInputParam);
+			// If there wasn't an error (which would return an empty string), display the results
 			if (!outString[0].isEmpty()) {
 				Output.printColorln(Ansi.Color.YELLOW, outString[0]);
 				Output.printColorln(Ansi.Color.WHITE, outString[1]);
@@ -450,10 +451,17 @@ public static void Parse(StackObj calcStack, StackObj calcStack2, String cmdInpu
 					BigDecimal fracTop = new BigDecimal(cmdInputParam.substring(0, cmdInputParam.indexOf('/')));
 					BigDecimal fracBottom = new BigDecimal(cmdInputParam.substring(cmdInputParam.indexOf('/') + 1));
 
+					Output.debugPrintln("Fraction Top:\t"+fracTop);
+					Output.debugPrintln("Fraction Bot:\t"+fracBottom);
+
 					// Divide the fraction and get a decimal equivalent
 					fracDecimalEquiv = fracTop.divide(fracBottom, MathContext.DECIMAL128);
 
 					// Overall decimal equivalent (integer + decimal)
+					// If integer is negative, make the decimal negative so we can add them
+					if (fracInteger.signum() < 0) {
+						fracDecimalEquiv = fracDecimalEquiv.multiply(new BigDecimal("-1"));
+					}
 					BigDecimal endResult = fracInteger.add(fracDecimalEquiv);
 
 					// Simply convert the fraction to a decimal and add it to the stack

src/main/java/org/fross/rpncalc/StackCommands.java

@@ -739,8 +739,8 @@ public static void cmdRound(StackObj calcStack, String arg) {
 		try {
 			decimalPlaces = Integer.parseInt(arg);
 			// Ensure a negative number is not provided for decimal points to round
-			if (decimalPlaces <= 0) {
-				Output.printColorln(Ansi.Color.RED, "ERROR:  '" + arg + "' number of decimal places must be > 0");
+			if (decimalPlaces < 0) {
+				Output.printColorln(Ansi.Color.RED, "ERROR:  '" + arg + "' number of decimal places must be >= 0");
 				return;
 			}
 

src/main/java/org/fross/rpncalc/StackConversions.java

@@ -94,7 +94,7 @@ public static String[] cmdFraction(StackObj calcStack, String param) {
 		BigDecimal startingNumber = calcStack.peek();
 
 		// If starting number is negative, set a variable then remove the negative sign
-		if (startingNumber.compareTo(BigDecimal.ZERO) < 0) {
+		if (startingNumber.signum() < 0) {
 			negativeNumber = true;
 			startingNumber = startingNumber.abs();
 		}
@@ -111,16 +111,35 @@ public static String[] cmdFraction(StackObj calcStack, String param) {
 			return outputString;
 		}
 
+		// Round the decimal number to the right denominator
+		// IF MY_DIM != ((FLOOR((MY_DIM * 16) + 0.5)) / 16)
+		// Reference: https://community.ptc.com/t5/3D-Part-Assembly-Design/Rounding-decimals-to-the-nearest-fraction/td-p/657420
+		BigInteger roundedNumberTemp = BigInteger.ZERO;
+		BigDecimal roundedNumber = BigDecimal.ZERO;
+		try {
+			roundedNumberTemp = startingNumber.multiply(new BigDecimal(denominator)).add(new BigDecimal("0.5")).toBigInteger();
+			roundedNumber = new BigDecimal(roundedNumberTemp).divide(new BigDecimal(denominator));
+		} catch (ArithmeticException ex) {
+			// Ignore error where division doesn't equate to the exact value - we're estimating here...
+		}
+
 		// Determine the integer portion of the number
-		BigInteger integerPart = startingNumber.toBigInteger();
+		BigInteger integerPart = roundedNumber.toBigInteger();
 
-		// Determine the fractional portion as an double
-		BigDecimal decimalPart = startingNumber.subtract(new BigDecimal(integerPart));
+		// Need to make the decimal a fraction my multiplying by the 10ths.
+		// Determine the number of decimals places and multiply by 10
+		int scaleMultiplier = 10;
+		for (int i = 1; i < roundedNumber.scale(); i++) {
+			scaleMultiplier *= 10;
+		}
 
-		// Convert to a fraction with provided base
-		// This will round to the nearest integer by adding 1/2 to the number and getting it's integer value
-		BigDecimal numeratorNotRounded = decimalPart.multiply(new BigDecimal(denominator));
-		BigInteger numerator = numeratorNotRounded.add(new BigDecimal(".5")).toBigInteger();
+		// Numerator = decimal portion * scale so we have an integer
+		// Decimal = the scale.  
+		// Example: 0.25 becomes 25/100  |   0.123 becomes 123/1000
+		BigDecimal numeratorTemp = roundedNumber.subtract(new BigDecimal(integerPart));
+		numeratorTemp = numeratorTemp.multiply(BigDecimal.valueOf(scaleMultiplier));
+		BigInteger numerator = numeratorTemp.toBigInteger();
+		denominator = BigInteger.valueOf(scaleMultiplier);
 
 		// Get the Greatest Common Divisor so we can simply the fraction
 		BigInteger gcd = Math.GreatestCommonDivisor(numerator, denominator);
@@ -138,16 +157,17 @@ public static String[] cmdFraction(StackObj calcStack, String param) {
 
 		// Output the fractional display
 		// If there is no fractional result, remove it so we don't see '0/1'
-		String stackHeader = "-Fraction (Granularity: 1/" + (denominator.multiply(gcd)) + ")";
+		String stackHeader = "-Fraction (Granularity: 1/" + (param) + ")";
+		String result = integerPart + " " + ((numerator.compareTo(BigInteger.ZERO) == 0) ? "" : numerator.toString() + "/" + denominator);
+
+		// Header Top
 		outputString[0] = "\n" + stackHeader + "-".repeat(Main.configProgramWidth - stackHeader.length());
-		if (numerator.compareTo(BigInteger.ZERO) != 0) {
-			outputString[1] = " " + calcStack.peek().setScale(8, RoundingMode.HALF_UP) + " is approximately '" + integerPart + " " + numerator + "/"
-					+ denominator + "'";
-		} else {
-			outputString[1] = " " + calcStack.peek() + " does not have a fractional component with a base of " + (denominator.multiply(gcd));
-		}
+		// Results
+		outputString[1] = " " + calcStack.peek().setScale(5, RoundingMode.HALF_UP) + " is approximately '" + result.trim() + "'";
+		// Header Bottom
 		outputString[2] = "-".repeat(Main.configProgramWidth) + "\n";
-		outputString[3] = integerPart + " " + numerator + "/" + denominator;
+		// Results for testing
+		outputString[3] = result.trim();
 
 		return outputString;
 	}

src/main/java/org/fross/rpncalc/StackObj.java

@@ -152,7 +152,11 @@ public void push(BigDecimal item) {
 	 * @param item
 	 */
 	public void push(String item) {
-		calcStack.push(new BigDecimal(item, this.mc));
+		try {
+			this.calcStack.push(new BigDecimal(item, this.mc));
+		} catch (Exception ex) {
+			Output.printColorln(Ansi.Color.RED, "Error: " + ex.getMessage());
+		}
 	}
 
 	/**

src/test/java/org/fross/rpncalc/CommandParserTest.java

@@ -102,7 +102,7 @@ void testFractionInput() {
 
 		CommandParser.Parse(stk1, stk2, "-4 1/64", "-4", "1/64");
 		StackCommands.cmdRound(stk1, "4");
-		assertEquals(-3.9844, stk1.peek().doubleValue());
+		assertEquals(-4.0156, stk1.peek().doubleValue());
 		assertEquals(4, stk1.size());
 
 		// Test scientific notation

src/test/java/org/fross/rpncalc/StackCommandsTest.java

@@ -1068,6 +1068,10 @@ void testCmdRound() {
 		stk.push(-65.4329);
 		StackCommands.cmdRound(stk, "12");
 		assertEquals(-65.4329, stk.pop().doubleValue());
+
+		stk.push(0.1);
+		StackCommands.cmdRound(stk, "0");
+		assertEquals(0, stk.pop().doubleValue());
 
 		// Scientific Notation
 		stk.push(1.23456789e19);