声明一个常量。
const(name = value)
const name = value
const WIDTH = 6
const HEIGHT = 8
@StartRule
Lot --> primitiveCube(WIDTH, 0.2, WIDTH)
extrude(HEIGHT)
comp(f) { top: Roof | side: Wall }
Roof --> color(0.5, 0.25, 0.15)
Wall --> color(0.75, 0.72, 0.68)