fn:round, rounding -ve to 0, we must return -0

Changes for rounding of types (DoubleValue, FloatValue) which distinguish -0 from 0.

Author: alanpaxton

exist-core/src/main/java/org/exist/xquery/functions/fn/FunRoundBase.java

@@ -28,6 +28,7 @@
 import org.exist.xquery.value.*;
 
 import java.math.RoundingMode;
+import java.util.Objects;
 
 /**
  * Base class for rounding mode functions
@@ -63,16 +64,46 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
         }
 
         final RoundingMode roundingMode = getFunctionRoundingMode(value);
-        
+
         if (args.length > 1) {
             final Item precisionItem = args[1].itemAt(0);
             if (precisionItem instanceof IntegerValue) {
                 final IntegerValue precision = (IntegerValue) precisionItem;
-                return value.round(precision, roundingMode);
+                return convertValue(precision, value, roundingMode);
+            }
+        }
+
+        return convertValue(IntegerValue.ZERO, value, roundingMode);
+    }
+
+    /**
+     * Apply necessary conversions to/from decimal to perform rounding in decimal
+     *
+     * @param precision precision of rounding
+     * @param value to round
+     * @param roundingMode mode to round in
+     * @return rounded value in decimal converted back to the input type
+     * @throws XPathException if a conversion goes wrong (it shouldn't)
+     */
+    private static Sequence convertValue(final IntegerValue precision, final NumericValue value, final RoundingMode roundingMode) throws XPathException {
+        final DecimalValue decimal = (DecimalValue)value.convertTo(Type.DECIMAL);
+        final DecimalValue rounded = (DecimalValue) Objects.requireNonNull(decimal).round(precision, roundingMode);
+
+        if (value.isNegative() && rounded.isZero()) {
+            //Extreme care!! (AP) -0 as DecimalValue will not be negative, -0.0f and -0.0d will be negative.
+            //So we need to test that original value to decide whether to negate a "zero" result.
+            //DecimalValue(s) are not necessarily normalized, but the 0-test will work..
+            switch (value.getType()) {
+                case Type.DOUBLE:
+                    return new DoubleValue(-0.0d);
+                case Type.FLOAT:
+                    return new FloatValue(-0.0f);
+                default:
+                    break;
             }
         }
 
-        return value.round(IntegerValue.ZERO, roundingMode);
+        return rounded.convertTo(value.getType());
     }
 
 }

exist-core/src/main/java/org/exist/xquery/value/DecimalValue.java

@@ -209,6 +209,7 @@ public boolean hasFractionalPart() {
     /* (non-Javadoc)
      * @see org.exist.xquery.value.Sequence#convertTo(int)
      */
+    @Override
     public AtomicValue convertTo(int requiredType) throws XPathException {
         switch (requiredType) {
             case Type.ATOMIC:

exist-core/src/test/xquery/numbers/fn-round.xqm

@@ -117,18 +117,30 @@ function fr:round-half-to-even($number as xs:double) {
 declare
     %test:args("-0.41",1)
     %test:assertEquals("-0.4")
-    %test:args("-0.41",0)
+    %test:args("-0.43",0)
     %test:assertEquals("-0")
+    %test:args("-0.43",0)
+    %test:assertEquals("0")
+    %test:args("-0.43",0)
+    %test:assertEquals(0)
 function fr:round-negative-zero($number as xs:decimal, $precision as xs:integer) {
     fn:round($number, $precision)
 };
 
-
 declare
     %test:args("-0.41",1)
     %test:assertEquals("-0.4")
     %test:args("-0.41",0)
     %test:assertEquals("-0")
 function fr:round-negative-zero-double($number as xs:double, $precision as xs:integer) {
     fn:round($number, $precision)
+};
+
+declare
+    %test:args("-0.41",1)
+    %test:assertEquals("-0.4")
+    %test:args("-0.41",0)
+    %test:assertEquals("-0")
+function fr:round-negative-zero-float($number as xs:float, $precision as xs:integer) {
+    fn:round($number, $precision)
 };