Re: Insulating data from code
- To: mathgroup at smc.vnet.net
- Subject: [mg66575] Re: Insulating data from code
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Sat, 20 May 2006 04:47:58 -0400 (EDT)
- Organization: The University of Western Australia
- References: <e4ekai$9av$1@smc.vnet.net> <e4jtnn$d02$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <e4jtnn$d02$1 at smc.vnet.net>, Peter Pein <petsie at dordos.net>
wrote:
> Ray Koopman schrieb:
> >>From time to time I've wanted to partition the first level of one
> > list, say A, the same way that another list, say B, is partitioned.
> > One way to do this is
> >
> > copyPartition[A_List, B_List] /; Length@A >= Length@Flatten@B :=
> > Module[{i = 0}, Map[A[[++i]]&,B,{-1}]]
> >
> > But all the methods I've thought of have a pointer that functions
> > something like i in the above code. I'd like to eliminate the pointer,
> > because in the unlikely event that A contains an unevaluated symbol
> > that is the same as the name of the pointer with $ appended -- e.g.,
> > i$, if the pointer is i -- then in the returned list that symbol will
> > have a numeric value assigned to it. Unique[i] doesn't help. The
> > only solution I see is the probabilistic one of giving the pointer a
> > strange (random?) name that hopefully would be very unlikely to show
> > up as data. But that would be giving up. Does anyone have any ideas?
> >
> Hi Ray,
>
> use Replace[]:
>
> A={a,b,c,d,e};
> B={{1},{2,3},{{{4}},5}};
>
> Ap=B/.Thread[Flatten[B]\[Rule]A]
> --> {{a},{b,c},{{{d}},e}}
No, that won't work. Try
A={a,b,c,d,a};
B={{1},{2,1},{{{3}},2}};
Ap=B/.Thread[Flatten[B] -> A]
You get
{{a}, {b, a}, {{{d}}, b}}
whereas I think the OP wanted
{{a}, {b, c}, {{{d}}, a}}
Cheers,
Paul
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