prototyping (oh no! not again??)

[brian_helterline]

davis at pacific.mps.ohio-state.edu ("John E. Davis") writes:
:In article <1990Nov28.010539.22412 at druid.uucp> darcy at druid.uucp (D'Arcy J.M. Cain) writes:
:   In <DAVIS.90Nov26144044 at pacific.mps.ohio-state.edu> John E. Davis writes:
:   >   double trace(double **matrix, int dim)
:   >   {
:   >      int i;
:   >      double t;
:   >
:   >      t = 0.0;
:   >      i = 0;
:   >      while(i++ < dim) t = t + matrix[i][i];

:   My first reaction was that you wind up accessing matrix[10][10] so you are
:   accessing an area outside of the array.  you should use:
:       for (i = 0; i < dim; i++) ...
:   but that doesn't explain why it works when you use:
:   >    double trace(double matrix[10][10],int n)
:   unless that changes the program just enough that the area following
:   the array is now part of your data space.  If so that is just bad news
:   somewhere else anyway.  Try using the for construct.


:This is not the function that I really had in mind.  I 'invented' this one as
:I was composing the article as a quick example the make my point.  I guess I
:should write:   
:               i = 0; while(i < dim) t = t + matrix[i][i++];
						     ^^^^^^^
	Wrong again!  There is no guarantee that this will evaluate to
	what you want.  If i=5, you could end up with matrix[6][5].
	Using a variable more than once in an expression with a post-
	increment is *undefined behavior*.

	What do you have against a for(i=0; i<dim; ++i ) loop?

	
:I noticed this after I posted it.

[rest deleted]