Auxiliary functions may be declared by defining them after the dynamical system equations. They should have the same format as the dynamical system, but do not use the prime after the name of the auxiliary function. RANGE may not be specified for auxiliary functions. For example, in the Van der Pol system:
# The Van der Pol oscillator (vanderpol.def) x' = y y' = alpha (1 - x^2) y - x + beta cos(omega t) t' = 1 Rsqr = x x + y y # square of polar radial coordinate INITIAL alpha 1.0 beta 0 omega 1.0 RANGE x 3 -3 y 3 -3