###
### ROOTS.R  Matlab ROOTS Function
###

roots <- function(p) {
    if (is.null(p) || length(p) == 0) return(matrix(0, nrow=0, ncol=0))
    if ( !is.vector(p, mode="numeric"))
        stop("Argument p must be a vector of real numbers.")
    if (length(p) == 1) return(matrix(0, nrow=0, ncol=0))

    # Find non-zero entries in p
    inz <- which(p != 0)
    nnz <- length(inz)
    if (nnz == 0) return(c())

    # Strip leading and trailing zeros, but remember the trailing zeros
    q <- p[inz[1]:inz[nnz]]
    r <- rep(0, length(p) - inz[nnz])

    A <- compan(q)
    return(c(r, eig(A)))
}