copula:::perspMvdc( )??中三個(gè)冒號(hào)似的符號(hào)表示什么意思？

某號(hào)后面這是個(gè)函數(shù)，一個(gè)叫叫Mvdc的函數(shù)。打算想知道改函數(shù)的調(diào)用方式、參數(shù)等說(shuō)明文檔，可以如下操作

function (x, FUN, xlim, ylim, n.grid = 26, xlab = "x1", ylab = "x2",
? ? zlab = deparse(substitute(FUN))[1], theta = -30, phi = 30,
? ? expand = 0.618, ticktype = "detail", ...)
{
? ? stopifnot(n.grid >= 2)
? ? if (length(n.grid) == 1)
? ?? ???n.grid <- rep(n.grid, 2)
? ? stopifnot(length(n.grid) == 2)
? ? x. <- seq(xlim[1], xlim[2], length.out = n.grid[1])
? ? y. <- seq(ylim[1], ylim[2], length.out = n.grid[2])
? ? grid <- as.matrix(expand.grid(x = x., y = y., KEEP.OUT.ATTRS = FALSE))
? ? z.mat <- matrix(if (chkFun(FUN))
? ?? ???FUN(grid, x)
? ? else FUN(x, grid), ncol = n.grid[2])
? ? T <- persp(x = x., y = y., z = z.mat, xlab = xlab, ylab = ylab,
? ?? ???zlab = zlab, theta = theta, phi = phi, expand = expand,
? ?? ???ticktype = ticktype, ...)
? ? invisible(list(x = x., y = y., z = z.mat, persp = T))
}

這是包里的內(nèi)部函數(shù)。