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MathGroup Archive 2001

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Re: Mapping a scalar against a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28406] Re: [mg28393] Mapping a scalar against a list
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Mon, 16 Apr 2001 03:29:00 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

It seems to me that this is one of those problems solutions to which can be
multiplied ad infinitum. Here is just one attempt:

In[1]:=
MyMap[f_, {a_, l_List}] := f @@@ (Hold[a, #] & /@ l)

In[2]:=
{a, l, f} = {"dog", {"dog", "cat", "mouse"}, f = StringMatchQ};

In[3]:=
MyMap[f, {a, l}]

Out[3]=
{True, False, False}

Hold as such plays no role here, you could replace it by lots of other
reasonable things.

-- 
Andrzej Kozlowski
Toyama International University
JAPAN

http://platon.c.u-tokyo.ac.jp/andrzej/



on 01.4.15 1:13 PM, Mark Coleman at mcoleman at bondspace.com wrote:

> Greetings,
> 
> I've recently been working on a problem involving determining whether a
> given string is contained in a large list of strings. Ideally, the problem
> would be solved by a 'Map' function 'M' defined as
> 
> M[f,{a,{b,c,d,...}}]= {f[a,b],f[a,c],f[a,d],...}
> 
> For this particular problem, {a} is a stiring, and {b,c,d,...} is a list of
> strings, then f=StringMatchQ. The function 'M' does not appear to match up
> against the standard Mathematica list functions. My current solution is to
> 'expand'
> the list {a} into a list of size Dimension[{b,c,d,...}] and then use
> MapThread. But this does not seem particularly elegant, especially if the
> list is very large.
> 
> Any suggestions would be most welcome!
> 
> Thanks,
> 
> Mark
> 
> 
> 




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