Added Register operation

src/core/FlowControl.js

@@ -90,6 +90,66 @@ const FlowControl = {
     },
 
 
+    /**
+     * Register operation.
+     *
+     * @param {Object} state - The current state of the recipe.
+     * @param {number} state.progress - The current position in the recipe.
+     * @param {Dish} state.dish - The Dish being operated on.
+     * @param {Operation[]} state.opList - The list of operations in the recipe.
+     * @returns {Object} The updated state of the recipe.
+     */
+    runRegister: function(state) {
+        const ings = state.opList[state.progress].getIngValues(),
+            extractorStr = ings[0],
+            i = ings[1],
+            m = ings[2];
+
+        let modifiers = "";
+        if (i) modifiers += "i";
+        if (m) modifiers += "m";
+
+        const extractor = new RegExp(extractorStr, modifiers),
+            input = state.dish.get(Dish.STRING),
+            registers = input.match(extractor);
+
+        /**
+         * Replaces references to registers (e.g. $R0) with the contents of those registers.
+         *
+         * @param {string} str
+         * @returns {string}
+         */
+        function replaceRegister(str) {
+            // Replace references to registers ($Rn) with contents of registers
+            str = str.replace(/((?:^|[^\\])(?:\\.|[^\\])*?)\$R(\d{1,2})/g, (match, pre, regNum) => {
+                const index = parseInt(regNum, 10) + 1;
+                return (index >= registers.length) ? match : pre + registers[index];
+            });
+
+            // Unescape remaining register references
+            return str.replace(/\\\$R(\d{1,2})/, "$R$1");
+        }
+
+        // Step through all subsequent ops and replace registers in args with extracted content
+        for (let i = state.progress + 1; i < state.opList.length; i++) {
+            let args = state.opList[i].getIngValues();
+            args = args.map(arg => {
+                if (typeof arg !== "string" && typeof arg !== "object") return arg;
+
+                if (typeof arg === "object" && arg.string) {
+                    arg.string = replaceRegister(arg.string);
+                    return arg;
+                }
+
+                return replaceRegister(arg);
+            });
+            state.opList[i].setIngValues(args);
+        }
+
+        return state;
+    },
+
+
     /**
      * Jump operation.
      *