[Axiom-math] recurrence relations -- HELP

[Martin Rubey]

I'd need a spad operation, that does the following:

given an EQ EXPR of the form

f_0*x(n) + f_1*x(n+1) + ... * f_k*x(n+k) = 0

where x is of type BasicOperator and the f_i are EXPR depending only on n

and initial values

x_1, x_2, x_3, ... x_(k-1)

calculate x(m) for given m.

I.e., if m is an integer m<k return x_m, otherwise compute recursively x_k,
x_(k+1) and so on.

if m is not an integer, return x(m) unevaluated.

For a start it does not have to be efficient!

(It is trivial in the interpreter, but I need a spad operation with signature,
say

evrec: EXPR INT, BOP, LIST EXPR INT -> EXPR INT

Martin