odeef.spad line 355 [edit on github]
NonLinearFirstOrderODESolver provides a function for finding closed form first integrals of nonlinear ordinary differential equations of order 1.
solve(M(x, y), N(x, y), y, x)
returns F(x, y)
such that F(x, y) = c
for a constant c
is a first integral of the equation M(x, y) dx + N(x, y) dy = 0
, or "failed" if no first-integral can be found.