Dear Kurt! As far as I can see, eval, D, == and := are behaving exactly as specified. With
f(x,y) == D(f(x,y),x) the symbol "f" is a FriCAS function, and NOT a function in the usual mathematical sense! In particular, f(a,b) returns the expression (in the pre-calculus sense) f_1(a,b), first derivative of with respect to the first argument, evaluated at a and b. Note that it is somewhat sloppy to write f_x(a,b) in calculus, because it is unclear what x refers to. Therefore, eval(f(a,b), b=a) must return f_1(a,a). On the other hand, f(a,a) should return the expression D(f(a,a), a), which is the derivative of f(a,a) with respect to a. Maybe the confusion comes from the difference between D and f_1: f_1(a,b) is the *result* of D(f(a,b), a). D is a FriCAS function, whereas f_1(a,b) is an expression. Martin -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/fricas-devel/e75c965b-4349-4913-9f52-4dae60d57c6a%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
