Possible Collect bug II
- To: mathgroup at yoda.ncsa.uiuc.edu
- Subject: Possible Collect bug II
- From: uunet!acf5.NYU.EDU!fink (Howard Fink)
- Date: Tue, 21 Aug 90 13:25:00 -0400
The following are the findings of John Mitchell reporting to mathgroup
August 21.
expr = -((-1)^(2n) y^2)/8 - ((-1)^(-1 + 2n) y^2)/8 + ((-1)^(1 + 2n) y^2)/8
2 n 2 -1 + 2 n 2 1 + 2 n 2
-((-1) y ) (-1) y (-1) y
------------- - ----------------- + -----------------
8 8 8
Collect[expr,y]
2 n 2
-3 (-1) y
-------------
8
(* This is incorrect *)
Factor[expr]
2 n 2
-((-1) y )
-------------
8
(* This is correct *)
*****************************
John Mitchell
Univ. of Chicago
5735 South Ellis Ave.
Chicago, IL 60637
(312) 702-7253
mitchell at pico.uchicago.edu
***********************************
I tried a few things and found this:
FixedPoint[Simplify, (expr - Simplify[expr])]
0
FixedPoint[Simplify, (expr - Collect[expr,y])]
2 n 2
(-1) y
------------
4
***********************************
Howard Fink
fink at acf5.nyu.edu