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package org.apache.poi.ss.formula.eval;
import junit.framework.ComparisonFailure;
import junit.framework.TestCase;
import org.apache.poi.ss.formula.functions.Function;
import org.apache.poi.util.HexDump;
/**
* IEEE 754 defines a quantity '-0.0' which is distinct from '0.0'.
* Negative zero is not easy to observe in Excel, since it is usually converted to 0.0.
* (Note - the results of XLL add-in functions don't seem to be converted, so they are one
* reliable avenue to observe Excel's treatment of '-0.0' as an operand.)
* <p/>
* POI attempts to emulate Excel faithfully, so this class tests
* two aspects of '-0.0' in formula evaluation:
* <ol>
* <li>For most operation results '-0.0' is converted to '0.0'.</li>
* <li>Comparison operators have slightly different rules regarding '-0.0'.</li>
* </ol>
* @author Josh Micich
*/
public final class TestMinusZeroResult extends TestCase {
private static final double MINUS_ZERO = -0.0;
public void testSimpleOperators() {
// unary plus is a no-op
checkEval(MINUS_ZERO, UnaryPlusEval.instance, MINUS_ZERO);
// most simple operators convert -0.0 to +0.0
checkEval(0.0, EvalInstances.UnaryMinus, 0.0);
checkEval(0.0, EvalInstances.Percent, MINUS_ZERO);
checkEval(0.0, EvalInstances.Multiply, MINUS_ZERO, 1.0);
checkEval(0.0, EvalInstances.Divide, MINUS_ZERO, 1.0);
checkEval(0.0, EvalInstances.Power, MINUS_ZERO, 1.0);
// but SubtractEval does not convert -0.0, so '-' and '+' work like java
checkEval(MINUS_ZERO, EvalInstances.Subtract, MINUS_ZERO, 0.0); // this is the main point of bug 47198
checkEval(0.0, EvalInstances.Add, MINUS_ZERO, 0.0);
}
/**
* These results are hard to see in Excel (since -0.0 is usually converted to +0.0 before it
* gets to the comparison operator)
*/
public void testComparisonOperators() {
checkEval(false, EvalInstances.Equal, 0.0, MINUS_ZERO);
checkEval(true, EvalInstances.GreaterThan, 0.0, MINUS_ZERO);
checkEval(true, EvalInstances.LessThan, MINUS_ZERO, 0.0);
}
public void testTextRendering() {
confirmTextRendering("-0", MINUS_ZERO);
// sub-normal negative numbers also display as '-0'
confirmTextRendering("-0", Double.longBitsToDouble(0x8000100020003000L));
}
/**
* Uses {@link ConcatEval} to force number-to-text conversion
*/
private static void confirmTextRendering(String expRendering, double d) {
ValueEval[] args = { StringEval.EMPTY_INSTANCE, new NumberEval(d), };
StringEval se = (StringEval) EvalInstances.Concat.evaluate(args, -1, (short)-1);
String result = se.getStringValue();
assertEquals(expRendering, result);
}
private static void checkEval(double expectedResult, Function instance, double... dArgs) {
NumberEval result = (NumberEval) evaluate(instance, dArgs);
assertDouble(expectedResult, result.getNumberValue());
}
private static void checkEval(boolean expectedResult, Function instance, double... dArgs) {
BoolEval result = (BoolEval) evaluate(instance, dArgs);
assertEquals(expectedResult, result.getBooleanValue());
}
private static ValueEval evaluate(Function instance, double... dArgs) {
ValueEval[] evalArgs;
evalArgs = new ValueEval[dArgs.length];
for (int i = 0; i < evalArgs.length; i++) {
evalArgs[i] = new NumberEval(dArgs[i]);
}
ValueEval r = instance.evaluate(evalArgs, -1, (short)-1);
return r;
}
/**
* Not really a POI test - just shows similar behaviour of '-0.0' in Java.
*/
public void testJava() {
assertEquals(0x8000000000000000L, Double.doubleToLongBits(MINUS_ZERO));
// The simple operators consider all zeros to be the same
assertTrue(MINUS_ZERO == MINUS_ZERO);
assertTrue(MINUS_ZERO == +0.0);
assertFalse(MINUS_ZERO < +0.0);
// Double.compare() considers them different
assertTrue(Double.compare(MINUS_ZERO, +0.0) < 0);
// multiplying zero by any negative quantity yields minus zero
assertDouble(MINUS_ZERO, 0.0*-1);
assertDouble(MINUS_ZERO, 0.0*-1e300);
assertDouble(MINUS_ZERO, 0.0*-1e-300);
// minus zero can be produced as a result of underflow
assertDouble(MINUS_ZERO, -1e-300 / 1e100);
// multiplying or dividing minus zero by a positive quantity yields minus zero
assertDouble(MINUS_ZERO, MINUS_ZERO * 1.0);
assertDouble(MINUS_ZERO, MINUS_ZERO / 1.0);
// subtracting positive zero gives minus zero
assertDouble(MINUS_ZERO, MINUS_ZERO - 0.0);
// BUT adding positive zero gives positive zero
assertDouble(0.0, MINUS_ZERO + 0.0); // <<----
}
/**
* Just so there is no ambiguity. The two double values have to be exactly equal
*/
private static void assertDouble(double a, double b) {
long bitsA = Double.doubleToLongBits(a);
long bitsB = Double.doubleToLongBits(b);
if (bitsA != bitsB) {
throw new ComparisonFailure("value different to expected",
HexDump.longToHex(bitsA), HexDump.longToHex(bitsB));
}
}
}