Re: Help with Hold
- To: mathgroup at smc.vnet.net
- Subject: [mg100976] Re: Help with Hold
- From: Peter Breitfeld <phbrf at t-online.de>
- Date: Thu, 18 Jun 2009 20:50:28 -0400 (EDT)
- References: <h1cv8s$jfg$1@smc.vnet.net>
Erich Neuwirth wrote:
> How can I transform
> Hold[x,Null,y,Null,Null]
> into
> {"x",Null,"y",Null,Null}
> even if x and/or y have assigned values?
>
Do you want something like this:
stringList[expr_]:=
List @@ Fold[ReplacePart[#1, #2 -> Extract[#1, #2, ToString]] &, expr,
Reverse[Sort[pos]]] // InputForm
Clear[x,y]
hh=Hold[x,Null,y,Null,Null]
In= stringList[hh]
Out={"x", "Null", "y", "Null", Null}
In= y=2; stringLst[hh]
Out={"x", "Null", "2", "Null", Null}
--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de