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MathGroup Archive 2002

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RE: Working with Strings

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35059] RE: [mg35021] Working with Strings
  • From: "DrBob" <majort at cox-internet.com>
  • Date: Thu, 20 Jun 2002 23:55:10 -0400 (EDT)
  • Reply-to: <drbob at bigfoot.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Here's an option (within a session):

mystring = {"cis-3-hexene", "acetone"};
Off[DeleteFile::"nffil"]
DeleteFile["tmp"]
On[DeleteFile::"nffil"]
Save["tmp", mystring];
Clear[mystring]
Get["tmp"];
mystring

DumpSave can replace Save, and may be more efficient.  With Save, you
can look at the contents of "tmp" to see what's going on.  You'll see
that this method doesn't require you to know what variables you're
reading with Get.

You could communicate between sessions by writing to an external file
like that, but I suspect you're already using a stream of some sort.
I've never seen that done between sessions, so I can't guess the easiest
way to modify what you're doing.  In general, you definitely need to
read the data a different way and possibly to write it a different way.

Bobby Treat

-----Original Message-----
From: Brian Higgins [mailto:bghiggins at ucdavis.edu] 
To: mathgroup at smc.vnet.net
Subject: [mg35059] [mg35021] Working with Strings

Hi Mathgroup,

In a webMathematica application I need to process string information.
The essential problem is as follows. The user selects  chemical
species such as

species1 = "cis-3-hexene";
species2 = "acetone"; 
  
Ideally these strings need to be processed into a list by using
AppendTo to obtain

mystring = {"cis-3-hexene", "acetone"}.

Then finally this list has to be converted to a string to be passed by
the web browser for another 'session',  as follows

In[13]:=ToString[mystring]

Out[13]="{cis-3-hexene, acetone}"

The problem is that in the new session I need to convert this string
back to a Mathematica expression for further processing, and when I do
this the data get corrupted:

In[14]:=ToExpression[ToString[mystring]]

Out[14]={-3 + cis - hexene, acetone}

I have figured a way around this problem but it is in my opinion
obtuse and I am looking for a more direct way to handle my problem.
Any thoughts?

Here is the way I handle it now.

Instead of using AppendTo I create the string for passing to the
browser as follows

ClearAttributes[Plus, Orderless]
specieslist = ToString[species1 + species2]

(Note the order is important)

In the new session this string is processed with the following
function

stringList[mylist_] := 
  Module[{aa}, 
    aa = DeleteCases[Characters[mylist], x_ /; x == " ", 
          Infinity] //. {x1___, "+", x2___} :> {{x1}, {x2}};
    Cases[aa, {x__String} :> StringJoin[x], Infinity]]

In[16]:=stringList[specieslist]

Out[16]={"cis-3-hexene", "acetone"}


Thanks in advance for any help you can offer,


Brian





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