Re: Modify a list of pure functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg70851] Re: [mg70812] Modify a list of pure functions*From*: Carl Woll <carlw at wolfram.com>*Date*: Sat, 28 Oct 2006 23:39:42 -0400 (EDT)*References*: <200610280921.FAA16098@smc.vnet.net>

. wrote: >Hi all, > >I have a problem where I need to build up a list of pure functions that >have been modified from a base pure function. I'm not having much luck >in getting it to work correctly, and was wondering if anyone had some >good ideas. A toy version of the problem is: > >f = Sin[#]& >listF = Table[(i f[##])&, {i, 5}] > >What I'd hope to get is listF containing: >{Sin[##]&, (2 Sin[##])&, (3 Sin[##])&, (4 Sin[##])&, (5 Sin[##])&} > >But instead, I get something where neither i nor f have been evaluated. > As I say, this is a toy example. One thing that does partially work >for the toy case, but does not seem to work for more complicated >situations is to use ReplaceAll: > >listF2 = Table[{j f[##])& /. j->i, {i,5}] > >This does give: >{1 f[##1] &, 2 f[##1] &, 3 f[##1]&, 4 f[##1] &, 5 f[##1] &} > >However, all that has been done is the index has been inserted; no >significant evaluation seems to have occurred. So this method doesn't >work in more complicated situations. For example, suppose insted of >using the index i directly, it actually referred to a list: > >coeffs = Reverse[ Range[5] ]; >listF3 = Table[ (coeffs[[j]] f[##]) & /. j->i, {i, 5}] > >This just gives: >{coeffs[[1]]*f[##1] & , coeffs[[2]]*f[##1] & , coeffs[[3]]*f[##1] & , >coeffs[[4]]*f[##1] & , coeffs[[5]]*f[##1] & } > >Which is no good if coeffs is a temporary variable. > >Any suggestions would be most appreciated. Thanks! > > Try using Evaluate: listF3 = Table[ Evaluate[coeffs[[i]] f[##]] &, {i,5}] Carl Woll Wolfram Research

**References**:**Modify a list of pure functions***From:*"." <ggroup@sarj.ca>