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From: stein-c@acsu.buffalo.edu (Craig Steinberger)
Newsgroups: comp.lang.fortran
Subject: Pointers in FORTRAN
Message-ID: <57829@eerie.acsu.Buffalo.EDU>
Date: 5 Feb 91 00:48:18 GMT
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Reply-To: stein-c@eng.buffalo.edu
Organization: SUNY at Buffalo-CFD Lab
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Hey Kids!

I am trying to use pointers in SunOS 4.1 Fortran. Below are two code
segments, and the output from each. Can anyone with experience tell me
what is happening and what I did wrong?

This program writes a number equal to the index of the array into each
array position, i.e. a(3,2,1)=321.0 It then writes it out to a file.

      program writeme
      real a(3,3,3)

      do 12 i=1,3
         do 11 j=1,3
            do 10 k=1,3
               a(i,j,k)=100.*float(i)+10.*float(j)+float(k)
 10         continue
 11      continue
 12   continue
      write(1,*)(((a(i,j,k),i=1,3),j=1,3),k=1,3)

And the output:

    111.000    211.000    311.000    121.000    221.000    321.000    131.000
    231.000    331.000    112.000    212.000    312.000    122.000    222.000
    322.000    132.000    232.000    332.000    113.000    213.000    313.000
    123.000    223.000    323.000    133.000    233.000    333.000

OK, so far so good. Now here's a program to read it back in. It then
writes the same thing right out again.
	program readme
      pointer(pa, a)
      real a(1,1,*)

      size=27*8
      pa=malloc(size)
      pia=malloc(size)
      read(1,*)(((a(i,j,k),i=1,3),j=1,3),k=1,3)
      write(2,*)(((a(i,j,k),i=1,3),j=1,3),k=1,3)

Here is the output from that:

    111.000    112.000    113.000    112.000    113.000    123.000    113.000
    123.000    133.000    112.000    113.000    123.000    113.000    123.000
    133.000    123.000    133.000    233.000    113.000    123.000    133.000
    123.000    133.000    233.000    133.000    233.000    333.000

Now, obviously either I screwed up or I don't understand how the pointer
concept works in FORTRAN, (Sun Fortran to be specific). My suspicion is
that I am off by one somehow. Can anyone help?
-- 
Craig Steinberger                               stein-c@eng.buffalo.edu
              SUNY at Buffalo, Computational Fluid Dynamics Lab