I agree entirely. Users should not have to have to think exactly how about polylog() and bessel_J() are defined.
John 2008/9/11 Jason Merrill <[EMAIL PROTECTED]>: > > On Sep 11, 9:07 am, "John Cremona" <[EMAIL PROTECTED]> wrote: >> This works: >> >> plot(lambda t:bessel_J(1, t), (1, 10)) >> >> so (1) a one-variable function is reequired, and the lambda >> construction creates such a function from the2-variable bessel_J, and >> (2) the range is a tuple (xmin,xmax) . >> >> John Cremona > > Is there a fundamental difference between bessel_J and, say, polylog, > for which I can do > > sage: plot(polylog(1,x),(x,.1,.9)) > > and I get a perfectly nice looking plot? > > I see that the implementation difference is that polylog is defined in > calculus.py, and is a class that derives from PrimitiveFunction, > whereas bessel_J is defined in special.py and is not a class, but just > a direct function definition. And the reason you can't do > > sage: plot(bessel_J(1, t), (t, 1, 10)) > > is that you can't partially evaluate a bessel_J function > > sage: bessel_J(1,t) > Traceback (click to the left for traceback) > ... > TypeError: Unable to convert x > (='1-1/8*t^2+1/192*t^4-1/9216*t^6+1/737280*t^8-1/88473600*t^10+1/1486356\ > 4800*t^12-1/3329438515200*t^14+1/958878292377600*t^16+O(t^17)') to > real > number. > > The lambda trick is certainly a sensible thing to do, but I can see > why it's difficult to guess that you should do that if you're just > thinking about things mathematically, rather than pythonically. > > We should think hard about making things easy to partially evaluate. > Why not have all the special functions behave like polylog? > Furthermore, it would ideally be easy for a user to define their own > functions that behave like polylog. > > Regards, > > JM > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
