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MathGroup Archive 2007

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Re: String to List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76995] Re: String to List
  • From: Szabolcs <szhorvat at gmail.com>
  • Date: Thu, 31 May 2007 03:29:13 -0400 (EDT)
  • Organization: University of Bergen
  • References: <f3jigv$dpo$1@smc.vnet.net>

King, Peter R wrote:
> I have a string which in general looks something like
> 
>  a="{x,16,x,1T,x}"
> 
> In other words it looks like a list with a mixture of characters and
> numbers and so on. I want to pick out the individual elements of this
> (using the commas as delimiters)
> 
> Clearly a[[1]] etc doesn't mean anything
> 
> I can do b=ToExpression[a] and I get a list so b[[1]] is x  and
> b[[2]]=16 (that is the number sixteen but I can convert this back into =
> a
> string with ToString. The problem is b[[4]] which ToExpression turns
> into T as it thinks I mean 1 x T.
> 
> So I would appreciate help with either
> 
> i) converting my original string to a list as I would like
> 
> Or
> 
> Ii) stopping the evaluation of 1T into T so that I can get the string 1T
> 
> (The only thought I had was to step through the original string
> character by character telling it to put the characters into different
> elements of a list each time  I pass a comma, but this looked a bit
> cumbersome).
> 
> Many thanks,
> 
> Peter King
> 

The best solution is to generate the data in a format that is easy to 
read for Mathematica, e.g. {"x", "16", "x", "1T", "x"}.

If you must do the conversion in Mathematica, try this (tested in v5.2):

In[1]:= a="{x,16,x,1T,x}"
Out[1]= {x,16,x,1T,x}

In[2]:= StringTake[a, {2,-2}]
Out[2]= x,16,x,1T,x

In[3]:= StringSplit[%, ","]
Out[3]= {x,16,x,1T,x}

Szabolcs

P.S. Is is possible to get Mathematica to print the quotes in standard 
form?  It is too easy to mistake string for symbols ...


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