Integration steps with multiple substitutions always use "u"

[agurney]

When asking for the integration steps for an integral where multiple substitutions are needed, the variable "u" is always used. For example, integrate(1/(x_log(x)_log(log(x)))) integrates to log(log(log(x))). Currently, two methods are reported: the first has us substituting u = log(x), and then substituting u = log(u). This second substitution ought not to reuse the variable u - it should say v = log(u), or in any case something that's not u or x. (The second method, substituting u = log(log(x)) in one go, is fine.)

[eagleoflqj]

Fixed at https://github.com/eagleoflqj/sympy_beta/commit/121079305305d5cf3ab9b574f2807c0feafc3900 Now step produced by https://sympy-beta.vercel.app/input/integrate%201%2F(x%20log(x)%20log(log(x))) is correct (though more complicated than it should be, which is a SymPy issue).