What poem is written by "the wall separated by three qins and the fog separated by five rivers" and what is its function?

Through this wall around the third district of Qin Dynasty, there is a layer of mist that unites the five rivers: it points out the farewell place and Du Shaofu's "dating" place, implying the meaning of farewell, and the weather is vigorous and open, which lays an optimistic and cheerful tone for the whole poem. It should be optimistic and cheerful! ! !

The sentence "I am worried about the bright moon in my heart, and I will follow you to Yelangxi" closely follows the above and focuses on expressing the poet's feelings here and now. The word "Jun" is called "Feng". The so-called "Yelang" here does not refer to Yelang Kingdom in the Han Dynasty, but Yelang County in the Sui Dynasty, which is located in Chenxi, Hunan Province today (see the Jade Emperor Ji Sheng, Volume 71). Longbiao is just to the west of Chenxi, so there is a saying that it is "until Yelangxi". The word "sad" in the sentence is also rich in content and worth pondering. Why are poets full of melancholy? It can be said that there is deep concern for the old friend, indignation at the reality at that time, sincere thoughts and sincere care. Before Wang Changling was demoted, he was Jiangning Cheng, and from Jiangning to Jiangzhong, he was Long Biao (see Fu Xuancong's poem in Tang Dynasty). Poets in Yangzhou can't say goodbye to their old friends face to face, so they have to entrust a deep affection to the bright moon and worry about missing them in the distance.

Distant friends bring distant land closer.