Re: Re: Unexpected non-evaluation problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg63157] Re: [mg63142] Re: Unexpected non-evaluation problem*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Fri, 16 Dec 2005 07:22:10 -0500 (EST)*References*: <dnrch3$kie$1@smc.vnet.net> <200512151107.GAA24729@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On 15 Dec 2005, at 20:07, Jean-Marc Gulliet wrote: > Carl Cotner wrote: >> I am totally baffled by the following Mathematica behavior: >> >> In[1]:= InverseFourierTransform[FourierTransform[x^2, x, y], y, x] >> Out[1]= Sqrt[2 Pi] x^2 FourierTransform[DiracDelta[y], y, x] >> >> In[2]:= Sqrt[2 Pi] x^2 FourierTransform[DiracDelta[y], y, x] >> Out[2]= x^2 >> >> I've already asked my local guru without success, so I'm hoping >> someone >> here can help me. Does anyone know why the first expression doesn't >> evaluate to x^2 all by itself? How I can force it to do so? >> >> Carl >> > Hi Carl, > > Mapping *Evaluate* to all parts will do it. Why? I do not know... > > In[1]:= > Evaluate //@ InverseFourierTransform[FourierTransform[x^2, x, y], > y, x] > > Out[1]= > x^2 > > Best regards, > /J.M. > Another possible workaround is to wrap Unevaluated around the argument of InverseFourierTransform: In[1]:= InverseFourierTransform[Unevaluated[FourierTransform[x^2, x, y]], y, x] Out[1]= x^2 Essentially the same approach is: InverseFourierTransform[FourierTransform[u, x, y], y, x] /. u -> x^2 x^2 There is no mystery why this works: both approaches are based on the obvious fact: InverseFourierTransform[FourierTransform[u, x, y], y, x] u It seems hard to tell what causes the original problem, except that it is certainly a bug. Andrzej Kozlowski

**References**:**Re: Unexpected non-evaluation problem***From:*Jean-Marc Gulliet <jeanmarc.gulliet@gmail.com>