text: 'use strict';
  
  var regExp = /%s/;
  
  // TODO: use o2.string when it’s ready.
  exports.printf = function(str) {
      var index = 1;
  
      while (arguments[index] !== undefined) {
          str = str.replace(regExp, arguments[index]);
  
          index++;
      }
  
      return str;
  };
  