[v1 v2 ...] fromVectors [s1 s2 ...]
array of poly : v1, v2, ... ; poly : s1, s2 ....
cf. toVectors. <<e_>> varaible is assumed to be the last
variable in x. @@@.esymbol
Example: [(x,y) ring_of_differential_operators 0] define_ring
[(x). (y).] /ff set
[ff ff] fromVectors ::