code: function(_part){
          if (_part[2]!='as')
              throw 'bad for list loop statement: '+_part.join(' ');
          var _seq = _part[1].split('..');
          if (_seq.length>1){
              // {list 1..100 as x}
              _doParseVars(_seq[0]);
              _doParseVars(_seq[1]);
              return 'for(var '+_part[3]+','+_part[3]+'_index=0,'+
                          _part[3]+'_beg='+_seq[0]+','+_part[3]+'_end='+_seq[1]+','+
                          _part[3]+'_length=parseInt('+_part[3]+'_end-'+_part[3]+'_beg+1);'+
                          _part[3]+'_index<'+_part[3]+'_length;'+_part[3]+'_index++){'+
                          _part[3]+' = '+_part[3]+'_beg+'+_part[3]+'_index;';
          }else{
              // {list seq as x}
              // seq is array [1,2,4]
              _doParseVars(_part[1]);
              return 'for(var __LIST__'+_part[3]+' = '+_part[1]+','+
                          _part[3]+','+_part[3]+'_index=0,'+
                          _part[3]+'_length=__LIST__'+_part[3]+'.length;'+
                          _part[3]+'_index<'+_part[3]+'_length;'+_part[3]+'_index++){'+
                          _part[3]+' = __LIST__'+_part[3]+'['+_part[3]+'_index];';
          }
      }
docs: /*
  解析{list seq as x}或者{list 1..100 as x}字符串的前缀
  @param  {Array}  按空格拆分的值,['list','seq','as','x']
  @return {String} 解析后的前缀值