Re: Distinquishing #'s in nested pure functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg126279] Re: Distinquishing #'s in nested pure functions*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Sat, 28 Apr 2012 05:28:15 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201204260933.FAA05752@smc.vnet.net>

f[x_, y_] := x - y f[x, y] // FullForm Plus[x,Times[-1,y]] Plus is Listable, e.g., f[2, {-1, -2, -3}] {3, 4, 5} Consequently, the Map is not necessary Select[{1, 2, 3}, f[#, {-1, -2, -3}] == {3, 4, 5} &] {2} However, often it is necessary to use a helper function to avoid ambiguity, e.g., g[x_] := f[x, {-1, -2, -3}] Select[{1, 2, 3}, g[#] == {3, 4, 5} &] {2} Bob Hanlon On Fri, Apr 27, 2012 at 6:48 AM, Dave Snead <dsnead6 at charter.net> wrote: > Hi, > > Is there a way to distinguish the #'s in nested pure functions? > > As a simple example: > > f[x_, y_] := x - y > > Select[{1, 2, 3}, (f[#, #] & /@ {-1, -2, -3}) == {3, 4, 5} &] > > I want the 1st # to correspond with the outer & (the equal) > and the 2nd # with the inner & (the map) > The answer in this example should by {2} > (of course, the statement as written above does not do the job) > > Can Mathematica distinguish these #'s? > > Thanks in advance, > Dave Snead >

**References**:**NonlinearModelFit and Complex Data***From:*Maria <rouelli@gmail.com>