Re: Simplify with NestedLessLess?

*To*: mathgroup at smc.vnet.net*Subject*: [mg106543] Re: Simplify with NestedLessLess?*From*: Albert Retey <awnl at gmx-topmail.de>*Date*: Fri, 15 Jan 2010 07:00:35 -0500 (EST)*References*: <himsqd$jd0$1@smc.vnet.net>

Hi, > Please excuse if this has been answered before, but I can't find it. > > Is there some way to do a Simplify with assumptions using a > NestedLessLess or something similar? For example: > > d=a+b > Simplify[d,NestedLessLess[a,b]] > > Answer is: > a+b > > Answer should be: > b > I don't think that Simplify does provide the functionality you are searching for. It is a combination of replacing and Series that will do: expr=a+b Normal[Series[expr /. {a -> b*eps}, {eps, 0, 0}]] the idea is to first rewrite the expression you want to "simpify" in terms of the quantity that will be small, that is eps=a/b in this case, then you can use Series to expand the result. Using Normal will get rid of the O[eps] term, which you often want to get rid of. Further simplification with Simplify might then of course also possible for more complicated cases... I think that approach should also work with more compicated expressions, but there are probably limits... hth, albert