code: function () {
                  var c = input.charAt(i);
  
                  if (c === '>' || c === '+' || c === '~' || c === '|' || c === '^') {
                      i++;
                      if (input.charAt(i) === '^') {
                          c = '^^';
                          i++;
                      }
                      while (isWhitespace(input, i)) { i++; }
                      return new(tree.Combinator)(c);
                  } else if (isWhitespace(input, i - 1)) {
                      return new(tree.Combinator)(" ");
                  } else {
                      return new(tree.Combinator)(null);
                  }
              }
docs: Combinators combine elements together, in a Selector.  Because our parser isn't white-space sensitive, special care has to be taken, when parsing the descendant combinator, ` `, as it's an empty space. We have to check the previous character in the input, to see if it's a ` ` character. More info on how we deal with this in *combinator.js*.