[GitHub] [commons-numbers] aherbert commented on a diff in pull request #122: NUMBERS-186: Lists of Complex Numbers

[GitBox <gi...@apache.org>]

aherbert commented on code in PR #122:
URL: https://github.com/apache/commons-numbers/pull/122#discussion_r962331149


##########
commons-numbers-complex-arrays/src/main/java/org/apache/commons/numbers/complex/arrays/ComplexList.java:
##########
@@ -322,4 +325,79 @@ private String outOfBoundsMsg(int index) {
         return INDEX_MSG + index + SIZE_MSG + size;
     }
 
+    /**
+     * This class acts as an iterator over the ComplexList class.
+     */
+    private class ComplexCursor implements ComplexSink<Void> {
+
+        /**
+         * Index of element to be returned by subsequent call to next.
+         */
+        private int index;
+
+        /**
+         * The modCount value that the cursor believes that the backing List should have.
+         * If this expectation is violated, the cursor has detected concurrent modification.
+         */
+        private final int expectedModCount = modCount;
+
+        /**
+         * Checks if the iteration has more elements.
+         * @return true if the iteration has more elements.
+         */
+        public boolean next() {
+            return index != size;
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public Void apply(double real, double imaginary) {
+            ComplexList.this.realAndImagParts[index * 2] = real;
+            ComplexList.this.realAndImagParts[(index * 2) + 1] = imaginary;
+            return null;
+        }
+
+        /**
+         * Gets the real part \( a \) of the complex number \( (a + i b) \) in the list.
+         *
+         * @return The real part.
+         */
+        public double real() {
+            return ComplexList.this.realAndImagParts[index * 2];
+        }
+
+        /**
+         * Gets the imaginary part \( b \) of the complex number \( (a + i b) \) in the list.
+         *
+         * @return The imaginary part.
+         */
+        public double imag() {
+            return ComplexList.this.realAndImagParts[(index * 2) + 1];
+        }
+
+        /**
+         * Checks for concurrent modification by looking at the modCount.
+         * @throws ConcurrentModificationException if expected modCount isn't equal to modCount.
+         */
+        final void checkForComodification() {
+            if (modCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    /**
+     * Replaces each element of the list with the result of applying the operator to that element.
+     * @param operator The operator to apply to each element.
+     */
+    public void replaceAll(ComplexUnaryOperator<Void> operator) {
+        ComplexCursor cursor = new ComplexCursor();
+        while (cursor.next()) {

Review Comment:
   This still advances the index outside of the cursor. I think the cursor should have that responsibility.
   
   The cursor could be changed to use the action in a tryAdvance(action) pattern. Alternatively if the cursor will not be reused then it could be removed and the logic placed directly here. It would eliminate the object allocation and simplify the loop logic.
   
   ```Java
   final double[] parts = ...;
   final int m = size;
   for (int i = 0; i < m; i++) {
       final int index = i << 1;
       operator.apply(parts[index], parts[index + 1], (x, y) -> { parts[index] = x; parts[index + 1] = y; });
   }
   // check for comodification
   ```
   Doing it this way uses a local copy of the list and size for efficiency.



##########
commons-numbers-complex-arrays/src/test/java/org/apache/commons/numbers/complex/arrays/ComplexListFunctionsTest.java:
##########
@@ -0,0 +1,69 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.numbers.complex.arrays;
+
+import org.apache.commons.numbers.complex.Complex;
+import org.apache.commons.numbers.complex.ComplexFunctions;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.Collectors;
+
+public class ComplexListFunctionsTest {

Review Comment:
   These tests can be moved to ComplexListTest, or at least the test class should be commented to state what tests are in this that are not in ComplexListTest.



##########
commons-numbers-complex-arrays/src/test/java/org/apache/commons/numbers/complex/arrays/ComplexListFunctionsTest.java:
##########
@@ -0,0 +1,69 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.numbers.complex.arrays;
+
+import org.apache.commons.numbers.complex.Complex;
+import org.apache.commons.numbers.complex.ComplexFunctions;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.Collectors;
+
+public class ComplexListFunctionsTest {
+
+    @Test
+    void testComplexUnaryOperator() {
+        List<Complex> objectList = generateList(10);
+        ComplexList actualList = new ComplexList();
+        actualList.addAll(objectList);
+        objectList.replaceAll(Complex::conj);
+        actualList.replaceAll(ComplexFunctions::conj);
+        Assertions.assertEquals(objectList, actualList);
+    }
+
+    @Test
+    void testComplexBinaryOperator() {
+        List<Complex> objectList = generateList(10);
+        double r = 2;
+        double i = 3;
+        Complex multiplier = Complex.ofCartesian(r, i);
+        ComplexList actualList = new ComplexList();
+        actualList.addAll(objectList);
+        objectList.replaceAll(c -> c.multiply(multiplier));
+        actualList.replaceAll((x, y, action) -> ComplexFunctions.multiply(x, y, r, i, action));
+        Assertions.assertEquals(objectList, actualList);
+    }
+
+    @Test
+    void testComplexScalarFunction() {
+        List<Complex> objectList = generateList(10);
+        double factor = 2;
+        ComplexList actualList = new ComplexList();
+        actualList.addAll(objectList);
+        objectList.replaceAll(c -> c.pow(factor));
+        actualList.replaceAll((x, y, action) -> ComplexFunctions.pow(x, y, factor, action));
+        Assertions.assertEquals(objectList, actualList);
+    }
+
+    private List<Complex> generateList(int size) {

Review Comment:
   Can be static. Should have a comment indicating what the function generates



##########
commons-numbers-complex-arrays/src/test/java/org/apache/commons/numbers/complex/arrays/ComplexListTest.java:
##########
@@ -19,16 +19,15 @@
 
 import org.apache.commons.numbers.complex.Complex;
 import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.junit.jupiter.api.Test;

Review Comment:
   Reorganising imports should not be done



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