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From: davis@pacific.mps.ohio-state.edu ("John E. Davis")
Newsgroups: comp.lang.c
Subject: prototyping (oh no! not again??)
Message-ID: <DAVIS.90Nov26144044@pacific.mps.ohio-state.edu>
Date: 26 Nov 90 19:40:44 GMT
Sender: news@pacific.mps.ohio-state.edu
Reply-To: davis@pacific.mps.ohio-state.edu  (John E. Davis)
Distribution: comp
Organization: "Dept. of Physics, The Ohio State University"
Lines: 50

Hi,

   Sorry about this, I am sure many are sick of these type of questions.

   I have a function that takes a 2-d array of unknown dimension and does
   things with it.  How do I declare and call it?

   I tried this:

   double trace(double **matrix, int dim)
   {
      int i;
      double t;

      t = 0.0;
      i = 0;
      while(i++ < dim) t = t + matrix[i][i];
      return t;
   }
        

   int main()
   {
     double m[10][10],t;
     .
     .
     t = trace(m,10);
     .
     .
   }


This dumps core because of segmentation fault.  However, if I prototype trace
as:

    double trace(double matrix[10][10],int n)

then the program is fine. However, it looses its generality. What is wrong
with the first prototype? 

I am sure I am doing something wrong and there is a big lesson in store for
me.


         
--
John

  bitnet: davis@ohstpy
internet: davis@pacific.mps.ohio-state.edu