What is the difference between: sage: derivative(3*x,x)(2)
which gives an error, and sage: f(x) = 3*x sage: derivative(f,x)(2) which returns 3, and sage: f(x) = 3*x sage: derivative(f(x),x)(2) which also gives an error? On Aug 3, 8:41 pm, Roger <[EMAIL PROTECTED]> wrote: > Huh. > > I am pretty sure I tried the *exact same thing* and it failed. > Obviously not. > > On Aug 2, 12:10 pm, Robert Bradshaw <[EMAIL PROTECTED]> > wrote: > > > How about > > > sage: f(x) = 3*x^2+x-1 > > sage: f.derivative().derivative()(5) > > 6 > > > On Aug 2, 2008, at 6:17 AM, Roger wrote: > > > > How does one then deal with the case of trying to find the second > > > derivative of a quadratic polynomial at some particular point? I've > > > run into this myself - you can't evaluate the resulting constant. > > > Suggestions? > > > > On Aug 1, 8:51 pm, adrian <[EMAIL PROTECTED]> wrote: > > >> I see. > > > >> Thanks > > >> -Adrian. > > > >> On Aug 1, 5:25 pm, "William Stein" <[EMAIL PROTECTED]> wrote: > > > >>> On Fri, Aug 1, 2008 at 1:31 PM, adrian > > >>> <[EMAIL PROTECTED]> wrote: > > > >>>> Yes, this would work. > > > >>>> But (and this is what happened to me) if I define a function > > >>>> def foo(a,b): > > >>>> return a.function(x)(3),b.function(x)(3) > > > >>>> and I try > > >>>> foo(x,x+1) > > >>>> my code would work, > > >>>> but if I do foo(2,x+1) > > >>>> it will not. > > > >>>> This can be done with what you wrote, I guess: > > >>>> def foo(a,b): > > >>>> a=SR(a) > > >>>> b=SR(b) > > >>>> return a.function(x)(3), b.function(x)(3) > > > >>>> and I guess that is the reason why 3+x-x works, since it maps the > > >>>> Integer(3) to SR(3). This means that, in a way, the Integer > > >>>> ring is > > >>>> a subring of the Symbolic Ring, and probably could share its > > >>>> methods. > > >>>> There might be some more things under consideration. > > > >>>> But I think it would be better to add the method, unless it breaks > > >>>> something else. > > > >>> We should not add the method. If you add it for the integers, you > > >>> would then also want to add it for real numbers, double precision > > >>> numbers, > > >>> complex numbers, etc., etc., etc., and it would never work on > > >>> builtin python > > >>> types like float (where one can't add new methods). > > > >>> Much better is to do the following which will work in all cases: > > > >>> sage: def foo(a,b): > > >>> ... return SR(a).function(x)(3), SR(b).function(x)(3) > > >>> sage: foo(2,3) > > >>> (2, 3) > > >>> sage: foo(2,3*x + 5) > > >>> (2, 14) --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
