Long is used as a comitative preposition and as a conjunction, like Cantonese tung4; and is used for NP conjunction in English sources only, whereas Chinese sources as represented by Tong (1862) generally use juxtaposition.
Source: Tong 1862: VI.79
Source: Tong 1862: VI.39
Source: Tong 1862: IV.69
Source: Holman 1834: 110