Re: Custom sort a list of pairs

*To*: mathgroup at smc.vnet.net*Subject*: [mg73690] Re: [mg73633] Custom sort a list of pairs*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Sat, 24 Feb 2007 02:28:29 -0500 (EST)*Reply-to*: hanlonr at cox.net

sortPairs[items_]:=Sort[Sort[data,#1[[2]]<#2[[2]]&], #1[[1]]>=#2[[1]]&]; sortPairs[{{1,a},{2,a},{3,a},{1,b},{2,b},{1,c}}] {{3, a}, {2, a}, {2, b}, {1, a}, {1, b}, {1, c}} Bob Hanlon ---- planetmarshalluk at hotmail.com wrote: > Hi there, > > I've searched through existing posts to no avail, what I want to do is > this: > Sort a nested list of pairs, so that each pair is sorted by reverse > canonical order on its first element, and in normal order on its > second element. > > For example, I want some function > > sortPairs[items_] > > that when given the input > > {{ 1,a},{2,a},{3,a},{1,b},{2,b},{1,c}} > > produces the output > > {{3,a},{2,a},{2,b}{1,a},{1,b},{1,c}} > > Any help much appreciated. > > Thanks, > Andrew