I’m singing while you are dancing.
dancing ,sing a song.ing.singed a song.danced a long.
time.danceabsd.cn
匹配上面字符串中ing前面的字符。
答案：\b\w+(?=ing)\b
1.1.零宽断言
原文：http://www.cnblogs.com/yahutiaotiao/p/8030277.html
