You can look at polynomial inverses another way: evaluation and interpolation are inverses. Here is a simple example. x L y produces the polynomial with values y at points x using Lagrange interpolation. The relationships are then:
L=:] %. [ ^/ [: i. [: # [ c=:3 1 4 1 5 x=:0 1 3 4 5 y=:c p. x d=:x L y >./|d-c 1.21426e_9 This is one of the ideas behind the discrete Fourier transform. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
