code: function _repeat(stack,min,max,charEndIndex,s) {
      var last=stack[0],repeat={min:min,max:max,nonGreedy:false},
          charIndex=charEndIndex-1;
      if (last.chars && last.chars.length===1) charIndex=last.indices[0];
      if (last.type===EXACT_NODE) { // exact node only repeat last char
        var a={
          type:EXACT_NODE,
          repeat:repeat,chars:last.chars?last.chars:s[charIndex],
          indices:[charIndex]
        };
        if (last.indices[0]===charIndex) stack.shift(); // e.g. /a{n}/ should be only single node
        stack.unshift(a);
      } else {
        last.repeat=repeat;
      }
      _set(repeat,'beginIndex',charEndIndex-stack[0].indices[0]);
    }
docs: e.g. /a+/