Re: Re: Way to evaluate D[(1-x^2)y''[x],{x,n

*To*: mathgroup at smc.vnet.net*Subject*: [mg15004] Re: [mg14961] Re: [mg14914] Way to evaluate D[(1-x^2)y''[x],{x,n*From*: "Fred Simons" <wsgbfs at win.tue.nl>*Date*: Sat, 5 Dec 1998 01:30:10 -0500*In-reply-to*: <366332FB.2869539C@col2.telecom.com.co>*Sender*: owner-wri-mathgroup at wolfram.com

Jurgen, Rather in a hurry: Now I understand your question, glad to see that it was not really a question. Your proposal is a real improvement. Obviously there is something in Mathematica I do not understand. I had the idea that when Mathematica returns the original command, it will try to use other (in this case its own) rules. I was inspired by some Mathematica output of the form Integrate[.....] -> If[ condition, 12, Integrate[.....] ] where the third argument of If is identical to the command. But it does not work in this way, as your example (and a similar one from one of my collleagues) shows. I have to think it over. Many thanks, Fred (PS I just noticed that my private reaction to you was on the mailing list. I do not understand how that could have happened, anyway I apologize.)