Comment #15 on issue 1816 by ronan.l...@gmail.com: Adding partial derivatives and taking derivatives with respect to functions
http://code.google.com/p/sympy/issues/detail?id=1816
@Brian: Could you please explain the intended meaning of diff(f(g(x)), g(x)) and Derivative(f(g(x)), g(x)) in terms of mathematical objects, without conflating symbols with what they represent or using notational tricks? You lost me at the first sentence: f(x) isn't a function (f is) and it's not a symbol either, but rather an expression containing two symbols that represents the result of applying the function f to x.
Anyway, it seems that what you have in mind is implicit functions, not functionals as I first understood. In that case, the relation d/df df/dx = 0 is obviously wrong, because derivations aren't necessarily commutative - take f = exp(x) for a counter-example.
@asmeurer: I thought there were spaces where it is continuous, but I guess you're right. If so, it's even worse than what I said: a function that's nowhere continuous doesn't have a derivative!
-- You received this message because you are subscribed to the Google Groups "sympy-issues" group. To post to this group, send email to sympy-issues@googlegroups.com. To unsubscribe from this group, send email to sympy-issues+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy-issues?hl=en.
