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