Re: Through[(a+b+b)[x]]

*To*: mathgroup at smc.vnet.net*Subject*: [mg109186] Re: Through[(a+b+b)[x]]*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Fri, 16 Apr 2010 05:51:07 -0400 (EDT)*References*: <hq61oh$3h6$1@smc.vnet.net>

Derek Yates wrote: > Through[(a+b)[x]] yields a[x]+b[x] as expected, but Through[(a+b+b) > [x]] yields a[x]+(2b)[x]. Through[(2b)[x]] yields 2[x]b[x]. Now, I can > obviously get around this in this specific case, but generically is > there a way to solve this so that Through[(a+b+b)[x]] yields a[x] > +2b[x]? The case where I envisage this happening is when a sum of > functions is supplied (say, for a given value of y, Through[(f[y]+g[y] > +h[y]+j[y])[x]] and for some values of y, g = h. Then one will end up > with the problem above. Other than some post processing using pattern > matching, which feels a bit clunky, I can't think of a way around this. > Why not describe the problem you are trying to solve - probably there is a better way than using Through. As You presumably realise, a+b+b gets simplified before the Through operation is performed. David Bailey http://www.dbaileyconsultancy.co.uk