Unsorted moments, those with exponents are not in numeric order,
are created in the symmoments environment using the tounsorted
function to transform from the sorted moment. If symmoments does not
exist, the user is prompted to create it using symmoments <- new.env().
If the sorted moment does not exist, it is created.
Moments of lower dimension are not created; for example, if c(2,4) is input, m20 is created, but m2 is not.
Moments are named mij..l, e.g., m136.
If any exponent is greater than 9,
lower case letters and then upper case letters are used.
For example,
m3bA is the name of the moment c(3,11,36).
The largest exponent allowed by this scheme is 9+26+26=61,
If an object with a name of this form exists but is not an object of class "moment",
it is replaced (overwritten) by the moment object.