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MathGroup Archive 1995

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Re: Selection of sublist using Cases

  • To: mathgroup at
  • Subject: [mg852] Re: Selection of sublist using Cases
  • From: rubin at (Paul A. Rubin)
  • Date: Wed, 26 Apr 1995 00:19:22 -0400
  • Organization: Michigan State University

In article <3mvegd$r0s at>,
   sands at (Charlie Rosenthal) wrote:
->I wonder if someone could explain why the following doesn't
->seem to work, and hopefully, what might.
->I have a list such as:
->hullHL = {{12. , 34., 3, "POLY","aTop",{1.,2.,3.}},
->          {15. , 22., 2, "POLY","aBottom",{1.,2.,3.,4.}}
->           .      .   .    .         .          .
->           .      .   .    .         .          .
->          }
->I would like to form from this list a sublist consisting of all 
->elements of the form {x_Real,y_Real,z_Integer,s1_String,"aTop",d_List}.
->returns {}. Why? 
->Charlie E. Rosenthal, sands at
I pasted your example directly into Mma (other than the ellipsis in the 
definition of hullHL) and the Cases command worked.  So my best guess is 
whatever actually creates your list is giving some element a head other 
than what you think it is (Real, Integer, String, List), even though it 
prints similarly to the example above.  Try FullForm[ hullHL ] and see if 
anything untoward shows up.


* Paul A. Rubin                                  Phone: (517) 432-3509   *
* Department of Management                       Fax:   (517) 432-1111   *
* Eli Broad Graduate School of Management        Net:   RUBIN at MSU.EDU    *
* Michigan State University                                              *
* East Lansing, MI  48824-1122  (USA)                                    *
Mathematicians are like Frenchmen:  whenever you say something to them,
they translate it into their own language, and at once it is something
entirely different.                                    J. W. v. GOETHE

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