Re: Tilting at Windmills?

*To*: mathgroup at smc.vnet.net*Subject*: [mg62156] Re: Tilting at Windmills?*From*: dana.onthebeach at comcast.net (Dana DeLouis ("dana.onthebeach at comcast.net"))*Date*: Sun, 13 Nov 2005 02:08:36 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

HI. Here's my attempt. f[v_List]:=Module[{t}, t=Flatten[Thread[{v,v,v,v}]]; t=Take[t,{4,-4}]; Partition[t,2,2] ] f[{a,b,c,d,e}] {{a,b},{b,b},{b,c},{c,c},{c,d},{d,d},{d,e}} HTH Dana DeLouis "Matt" <anonmous69 at netscape.net> wrote in message news:dl1jta$1m$1 at smc.vnet.net... > Hello, > Where there's a chance of success, I tend to agonize over details of > implementation. Memory usage is one such area. Here is a statement of > a problem I was trying to solve in Mathematica: > > Given a list of the following form:{x1,x2,x3,...,xn-1,xn} I want to > develop an algorithm that will iterate over the input list to produce > output of the following > form:{x1,x2,x2,x2,x2,x3,x3,x3,x3,x4,x4,x4,x4,x5,...,xn-2,xn-1,xn-1,xn-1,xn-1,xn} > which will then need to be partitioned to end up in the following form: > {{x1,x2},{x2,x2},{x2,x3},{x3,x3},{x3,x4},{x4,x4},{x4,x5},...,{xn-2,xn-1},{xn-1,xn-1},{xn-1,xn}} > which means that if I had a flattened list of length'n' as input, then > the new flattened list would have a length of 4*(n-2)+2 > > Here is my first solution... <snip>