aherbert commented on code in PR #138:
URL: https://github.com/apache/commons-numbers/pull/138#discussion_r1341387578
##########
commons-numbers-core/src/main/java/org/apache/commons/numbers/core/Addition.java:
##########
@@ -44,4 +44,12 @@ public interface Addition<T> {
* @return {@code -this}.
*/
T negate();
+
+ /**
+ * Is this the zero element? Implementations may want to employ more
efficient
+ * means than calling equals on the zero element.
+ *
+ * @return {@code true} if {@code this} equals the result of {@link #zero}.
+ */
+ boolean isZero();
Review Comment:
We can maintain binary compatibility by adding a default method to the
interface:
```java
default boolean isZero() {
return this.equals(one());
}
```
##########
commons-numbers-core/src/main/java/org/apache/commons/numbers/core/Multiplication.java:
##########
@@ -44,4 +44,12 @@ public interface Multiplication<T> {
* @return <code>this<sup>-1</sup></code>.
*/
T reciprocal();
+
+ /**
+ * Is this the neutral element of multiplication? Implementations may want
to
+ * employ more efficient means than calling equals on the one element.
+ *
+ * @return {@code true} if {@code this} equals the result of {@link #one}.
+ */
+ boolean isOne();
Review Comment:
```java
default boolean isOne() {
return this.equals(one());
}
```
##########
commons-numbers-core/src/main/java/org/apache/commons/numbers/core/DD.java:
##########
@@ -1924,6 +1924,18 @@ public DD pow(int n) {
return computePow(x, xx, n);
}
+ /** {@inheritDoc} */
+ @Override
+ public boolean isZero() {
+ return equals(0.0, x) && equals(0.0, xx);
Review Comment:
The methods in this class assume a normalised representation such that `|x|
>= |xx|`. Thus we only need to compare `x` to zero.
Due to the use of binary equality this method will not return true for
`(-0.0, xx)`.
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