*To*: mathgroup@smc.vnet.net*Subject*: [mg11183] Efficient use of coefficient--Efficient simplification*From*: Joel Cannon <cannon@alpha.centenary.edu>*Date*: Wed, 25 Feb 1998 03:31:52 -0500*Organization*: Centenary College of Louisiana

I wish to simplify expressions such as the following which possess terms involving ket[n+i]. They involve a variable range of indices i. Out[164]= -(Sqrt[n] (Sqrt[-1 + n] ket[-2 + n] - Sqrt[n] ket[n])) + Sqrt[1 + n] (Sqrt[1 + n] ket[n] - Sqrt[2 + n] ket[2 + n]) I can collect the various terms in ket[n+i] with the following operation: In[176]:= Out[164]//Expand// Table[ket[n+i] Coefficient[#,ket[n+i] ],{i,-2,2}]& //Plus @@ #& Out[176]= -(Sqrt[-1 + n] Sqrt[n] ket[-2 + n]) + (1 + 2 n) ket[n] - Sqrt[1 + n] Sqrt[2 + n] ket[2 + n] My problem is this, Since I do no know what the range of ket[n+i] will be, I would like to write a general expression that will find what ket[n+i] are present and collect the coefficients of each of these. The inelegant wat is to run over a range of i's that will surely bracket any ket[n+i] that I will possibly encounter, but that is distasteful. I am using version 2.2 but will probably switch to 3.0 soon. Any other suggestions to that way I have done things are welcomed. If possible, please copy me on email since I might otherwise miss posts to the newsgroup. cannon@alpha.centenary.edu Thanks very much, ------------------------------------------------------------------------------ Joel W. Cannon | (318)869-5160 Dept. of Physics | (318)869-5026 FAX Centenary College of Louisiana | P. O. Box 41188 | Shreveport, LA 71134-1188 |