add Subtract op

src/core/operations/Subtract.mjs

@@ -0,0 +1,48 @@
+/**
+ * @author d98762625 [d98762625@gmail.com]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import Arithmetic from "./baseClasses/Arithmetic";
+import BigNumber from "bignumber.js";
+
+/**
+ * Subtract operation
+ */
+class Subtract extends Operation {
+
+    /**
+     * Subtract constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Subtract";
+        this.module = "Default";
+        this.description = "Subtracts a list of numbers. If an item in the string is not a number it is excluded from the list.<br><br>e.g. <code>0x0a 8 .5</code> becomes <code>1.5</code>";
+        this.inputType = "string";
+        this.outputType = "BigNumber";
+        this.args = [
+            {
+                "name": "Delimiter",
+                "type": "option",
+                "value": Arithmetic.DELIM_OPTIONS,
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {BigNumber}
+     */
+    run(input, args) {
+        const val = Arithmetic._sub(Arithmetic._createNumArray(input, args[0]));
+        return val instanceof BigNumber ? val : new BigNumber(NaN);
+    }
+
+}
+
+export default Subtract;