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

@@ -1 +1,15 @@
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+package com.example.util;
+
+public class SubtractFunction 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 -= input[i];
+        }
+        return result;
+    }
+}