Uploading the main structure

node_modules/token-stream/index.js

@@ -0,0 +1,30 @@
+'use strict';
+
+module.exports = TokenStream;
+function TokenStream(tokens) {
+  if (!Array.isArray(tokens)) {
+    throw new TypeError('tokens must be passed to TokenStream as an array.');
+  }
+  this._tokens = tokens;
+}
+TokenStream.prototype.lookahead = function (index) {
+  if (this._tokens.length <= index) {
+    throw new Error('Cannot read past the end of a stream');
+  }
+  return this._tokens[index];
+};
+TokenStream.prototype.peek = function () {
+  if (this._tokens.length === 0) {
+    throw new Error('Cannot read past the end of a stream');
+  }
+  return this._tokens[0];
+};
+TokenStream.prototype.advance = function () {
+  if (this._tokens.length === 0) {
+    throw new Error('Cannot read past the end of a stream');
+  }
+  return this._tokens.shift();
+};
+TokenStream.prototype.defer = function (token) {
+  this._tokens.unshift(token);
+};