Merge branch 'master' of https://github.com/unitsofmeasurement/indriya.git

Author: keilw

src/main/java/tech/units/indriya/function/DefaultNumberSystem.java

@@ -49,6 +49,9 @@
  */
 public class DefaultNumberSystem implements NumberSystem {
 
+    static final double MAX_LONG_AS_DOUBLE = Long.MAX_VALUE;
+    static final double MIN_LONG_AS_DOUBLE = Long.MIN_VALUE;
+
     /**
      *  In order of increasing number type 'widening'.
      */
@@ -163,7 +166,7 @@ static NumberType valueOf(final Number number) {
         /**
          * Whether given {@link Number} is ZERO.
          * @param number - must be of type {@link #getType()}
-         * @apiNote For class internal use only, 
+         * @apiNote For class internal use only,
          *      such that we have control over the number's type that gets passed in.
          */
         boolean isZero(Number number) {
@@ -466,8 +469,22 @@ public Number narrow(final Number number) {
             if(!Double.isFinite(doubleValue)) {
                 throw unsupportedNumberValue(doubleValue);
             }
-            if(doubleValue % 1 == 0 && !isZero(number)) {
+            if(doubleValue == 0) {
+                return 0;
+            }
+            if(doubleValue % 1 == 0) {
                 // double represents an integer other than zero
+
+                // narrow to long if possible
+                if(MIN_LONG_AS_DOUBLE <= doubleValue && doubleValue <= MAX_LONG_AS_DOUBLE) {
+                    long longValue = (long) doubleValue;
+
+                    // further narrow to int if possible
+                    if(Integer.MIN_VALUE <= longValue && longValue <= Integer.MAX_VALUE) {
+                        return (int) longValue;
+                    }
+                    return longValue;
+                }
                 return narrow(BigDecimal.valueOf(doubleValue));
             }
             return number;
@@ -781,7 +798,7 @@ private Number addWideAndNarrow(
     private Number multiplyWideAndNarrow(
             final NumberType wideType, final Number wide,
             final NumberType narrowType, final Number narrow) {
-        
+
         // shortcut if any of the operands is zero.
         if (wideType.isZero(wide)
                 || narrowType.isZero(narrow)) {

src/test/java/tech/units/indriya/function/DefaultNumberSystemTest.java

@@ -39,14 +39,18 @@
 
 import javax.measure.quantity.Dimensionless;
 
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Named;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
 import tech.units.indriya.AbstractUnit;
 import tech.units.indriya.ComparableQuantity;
@@ -212,7 +216,7 @@ static Stream<BigDecimal> provideNonFractionalBigDecimalSamples() {
                 BigDecimal.valueOf(1),
                 BigDecimal.valueOf(100, 2), // 100 * 10^-2 == 1
                 BigDecimal.valueOf(1, -2), // 1 * 10^2 == 100
-                new BigDecimal("1234.000") // trailing zeros, should not make this decimal a non integer 
+                new BigDecimal("1234.000") // trailing zeros, should not make this decimal a non integer
                 );
     }
     @ParameterizedTest
@@ -316,4 +320,18 @@ static Stream<Number> provideZeroSamples() {
                 );
     }
 
+
+    // -- NARROW TESTS
+    @Test
+    void narrow() {
+        assertInstanceOf(Integer.class, ns.narrow(0.0));
+        assertInstanceOf(Integer.class, ns.narrow(1.0));
+        assertInstanceOf(Integer.class, ns.narrow((double) Integer.MIN_VALUE));
+        assertInstanceOf(Integer.class, ns.narrow((double) Integer.MAX_VALUE));
+        assertInstanceOf(Long.class, ns.narrow(DefaultNumberSystem.MIN_LONG_AS_DOUBLE));
+        assertInstanceOf(Long.class, ns.narrow(DefaultNumberSystem.MAX_LONG_AS_DOUBLE));
+        // corner cases at the edge of the long range
+        assertInstanceOf(BigInteger.class, ns.narrow(Math.nextDown(DefaultNumberSystem.MIN_LONG_AS_DOUBLE)));
+        assertInstanceOf(BigInteger.class, ns.narrow(Math.nextUp(DefaultNumberSystem.MAX_LONG_AS_DOUBLE)));
+    }
 }