//SLUGens released under the GNU GPL as extensions for SuperCollider 3, by Nick Collins, http://composerprogrammer.com/index.html
Represents the arbitrary non-linear filter difference equation in the time domain:
y(n) = sum over terms of constant * product of x terms at individual powers * product of y terms at individual powers
This allows arbitrary crossterms in x and y, but is expensive to calculate.
Stability is definitely not guaranteed; most equations will quickly blow-up. See the guard arguments below. It is recommended that you stick to positive exponents for signals which are within -1 to 1, else explosion of values is inevitable.
(0.1)**(-1.26) //negative exponents cause blowup for smaller signals abs(sig) < 1.0
(1.1)**(2.26) //positive exponents cause blowup for larger signals abs(sig) > 1.0
You need to pass in the parameters via two buffers, of arbitrary size.
What do you want to filter?
A single buffer containing numcrossterms in the first index, then the specification of crossterms as (constant, num x terms, list of x index/exponent pairs, num y terms, list of y index/coefficient pairs). Buffer contents can be switched at run-time as longas this data format is strictly adherred to.
Maximum index stored for previous outputs
Maximum index stored for previous inputs
Watch out for blow-up and reset if necessary; this is the value of the maximum absolute output allowed.
Watch out for blow-up and reset if necessary; this is the value of the maximum absolute change of output allowed.
On discovering blow-up, filter output is set back to zero for all stored outputs, so that feedback cannot occur.