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I actually get
TypeError: unable to make sense of Maxima expression ...
when I try this. In fact,
sage: desolve_rk4(f(t,y), y, ivar=t, ics=[0,-4], end_points=[0,.4])
[[0, -4],
[0.1, -6.44026308551],
[0.2, -18.4360863753],
[0.3, -9638.98851821],
[0.4, -2.29907718472e+44]]
works, but
sage: desolve_rk4(f(t,y), y, ivar=t, ics=[0,-4], end_points=[0,.5])
TypeError: unable to make sense of Maxima expression '[[0,-4],[0.1,-6.440263085506939],[0.2,-18.436086375306434],[.30000000000000004,-9638.988518207414],[0.4,-229907718471530700000000000000000000000000000.],[0.5,-.000000000000000.000000000000000]]' in Sage
and indeed -.000000000000000.000000000000000 makes no sense inside of Sage. I'm not sure what it's supposed to mean in Maxima, either!
Here is the problem, in Maxima.
(%i1) rk(6+y-y^2,y,-4,[t,0,.5,.1]);
(%o1) [[0, - 4], [0.1, - 6.440263085506939], [0.2, - 18.436086375306434],
[.30000000000000004, - 9638.988518207414], [0.4, - 2.2990771847153071e+44],
[0.5, - .000000000000000e+4932]]
Apparently Sage doesn't know how to translate these. And what should zero times ten to the 4932 mean?
Anyway, I've opened Trac 15789 for this.
