# integrable.ode
# an integrable system with its integral
init x=.1,y=.2
x'=x*y+y^3
y'=-y^2/2+x^2*(1-x)
# here is the integral
aux i=x*y^2/2+y^4/4+x^4/4-x^3/3
aux li=log(abs(x*y^2/2+y^4/4+x^4/4-x^3/3))
@ xp=x,yp=y,xlo=-2,ylo=-2,xhi=2,yhi=2
@ total=100
@ back=white
done