RE: Padding arrays with reversed elements

*To*: mathgroup at smc.vnet.net*Subject*: [mg45685] RE: [mg45636] Padding arrays with reversed elements*From*: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>*Date*: Mon, 19 Jan 2004 05:15:30 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

>-----Original Message----- >From: Mariusz Jankowski [mailto:mjankowski at usm.maine.edu] To: mathgroup at smc.vnet.net >Sent: Saturday, January 17, 2004 1:57 AM >To: mathgroup at smc.vnet.net >Subject: [mg45685] [mg45636] Padding arrays with reversed elements > > >Hi all, a recently posted question on "creating a toroidal >data structure" >and the the responses have inspired me to post the following >similar but >harder problem. I am interested in "reflected" padding of >multidimensional >arrays. Here is an example in 1D: > >{a,b,c,d} -> {a,b,c,d,d,c,b,a,a,b,c,d,d,c, etc} > >also the padding should be possible on the left or right or both and of >course, the length is an argument. I have a complicated >looking solution >using PadRight, Fold, Partition and would love to see some >ideas leading to >a possibly simpler solution. > >Thanks, Mariusz > Mariuz, PadRight still going strong: In[1]:= r = {a, b, c, d}; In[2]:= rr = Join[r, Reverse[r]] Out[2]= {a, b, c, d, d, c, b, a} In[3]:= PadRight[rr, 14, rr] Out[3]= {a, b, c, d, d, c, b, a, a, b, c, d, d, c} In[4]:= PadRight[rr, 8, rr, 2] Out[4]= {b, a, a, b, c, d, d, c} -- Hartmut Wolf