       Re: Changing the Natural Sort Order

• To: mathgroup at smc.vnet.net
• Subject: [mg49163] Re: Changing the Natural Sort Order
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 6 Jul 2004 03:33:21 -0400 (EDT)
• Organization: Universitaet Leipzig
• References: <ccb5hr\$ekg\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

\$myOrder = {a, d, b, c, f};

Symbols[expr_] := Union[Cases[expr, _Symbol, Infinity]]
orderQ[expr_] := Min[Flatten[Position[\$myOrder, #] & /@ Symbols[expr]]]

In[]:=Sort[{h[x, g[a]], h[x, g[b]], h[x, g[c]], h[x, g[d]], h[x, g[f]]},
orderQ[#1] < orderQ[#2] &]

Out[]={h[x, g[a]], h[x, g[d]], h[x, g[b]], h[x, g[c]], h[x, g[f]]}

Regards
Jens

David Park wrote:
>
> Dear MathGroup,
>
> Is it possible to change the natural sort order of symbols that is used in Sort?
>
> I would like something like the following statement (that does not work).
>
> Assuming[d < b < c, Sort[{a, b, c, d, f}]]
>
> giving the desired output
>
> {a,d,b,c,f}
>
> I won't be sorting simple lists of symbols, but lists of similar, but unspecified, expressions that contain the symbols. For example...
>
> {h[x,g[a]], h[x,g[b]], h[x,g[c]], h[x,g[d]], h[x,g[f]]}
>
> which should give
>
> {h[x,g[a]], h[x,g[d]], h[x,g[b]], h[x,g[c]], h[x,g[f]]}
>
> Is there any way to do this?
>
> David Park