Bump to v4.7.0.

_createMathOperation.js

@@ -0,0 +1,24 @@
+/**
+ * Creates a function that performs a mathematical operation on two values.
+ *
+ * @private
+ * @param {Function} operator The function to perform the operation.
+ * @returns {Function} Returns the new mathematical operation function.
+ */
+function createMathOperation(operator) {
+  return function(value, other) {
+    var result;
+    if (value === undefined && other === undefined) {
+      return 0;
+    }
+    if (value !== undefined) {
+      result = value;
+    }
+    if (other !== undefined) {
+      result = result === undefined ? other : operator(result, other);
+    }
+    return result;
+  };
+}
+
+module.exports = createMathOperation;