If x is a yacas command as string, convert to a character vector/matrix in R.
If x is a yac_symbol (e.g. from ysym()), then convert it to a numeric object
if there are no variables or a character type if there are variables.
as_r(x)yacas list or list of lists to convert
In yacas a vector is a list, and a matrix is a list of lists.