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Re: Mapping and AppendTo

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91774] Re: Mapping and AppendTo
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sun, 7 Sep 2008 05:40:17 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <g9qimb$4fg$1@smc.vnet.net> <200809051113.HAA11749@smc.vnet.net> <g9t6op$jaj$1@smc.vnet.net>

Schettler, Martin wrote:

> I would like mix use of Map and AppendTo in the following way (e.g.):
> 
> M = {{0,1,2},{4,5,6,7}};
> AppendTo[#,8]&/@M;
> 
> Of course, this doesn't work, because {0,1,2} is not a symbol name,etc.
> Is there a way to use Hold or Sow to make this construct work?

It would be less troublesome to use Append or Riffle and reset the value 
of M. For instance,

In[1]:= M = {{0, 1, 2}, {4, 5, 6, 7}};
M = Append[#, 8] & /@ M

Out[2]= {{0, 1, 2, 8}, {4, 5, 6, 7, 8}}

In[3]:= M = {{0, 1, 2}, {4, 5, 6, 7}};
M = Riffle[#, 8, Length[#] + 1] & /@ M

Out[4]= {{0, 1, 2, 8}, {4, 5, 6, 7, 8}}

Regards,
-- Jean-Marc


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