Merge pull request 'feat: add power operation to calculator (#11)' (#12) from ai/issue-11 into main

Reviewed-on: #12

src/main/java/com/example/LoopTestApplication.java

@@ -4,6 +4,7 @@ import com.example.util.AddFunction;
 import com.example.util.CalcFunction;
 import com.example.util.DivideFunction;
 import com.example.util.MultiplyFunction;
+import com.example.util.PowerFunction;
 import com.example.util.SubtractFunction;
 
 public class LoopTestApplication {
@@ -18,5 +19,7 @@ public class LoopTestApplication {
         System.out.println("MULTIPLICATION: " + multiply.calc(2, 5, 6));
         CalcFunction divide = new DivideFunction();
         System.out.println("DIVISION: " + divide.calc(2, 5, 6));
+        CalcFunction power = new PowerFunction();
+        System.out.println("POWER: " + power.calc(2, 5, 6));
     }
 }

src/main/java/com/example/util/PowerFunction.java

@@ -0,0 +1,15 @@
+package com.example.util;
+
+public class PowerFunction implements CalcFunction {
+
+    public double calc(double... input) {
+        if (input.length == 0) {
+            return 0;
+        }
+        double result = input[0];
+        for (int i = 1; i < input.length; i++) {
+            result = Math.pow(result, input[i]);
+        }
+        return result;
+    }
+}

src/test/java/com/example/util/PowerFunctionTest.java

@@ -0,0 +1,35 @@
+package com.example.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class PowerFunctionTest {
+
+    private final PowerFunction powerFunction = new PowerFunction();
+
+    @Test
+    void raisesMultipleValuesLeftToRight() {
+        assertEquals(1073741824.0, powerFunction.calc(2.0, 5.0, 6.0));
+    }
+
+    @Test
+    void returnsSingleValue() {
+        assertEquals(5.0, powerFunction.calc(5.0));
+    }
+
+    @Test
+    void returnsZeroForNoInput() {
+        assertEquals(0.0, powerFunction.calc());
+    }
+
+    @Test
+    void raisesToNegativeExponent() {
+        assertEquals(0.25, powerFunction.calc(2.0, -2.0));
+    }
+
+    @Test
+    void raisesToZeroExponent() {
+        assertEquals(1.0, powerFunction.calc(7.0, 0.0));
+    }
+}