Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!uflorida!mailrus!cornell!batcomputer!lijewski
From: lijewski@batcomputer.tn.cornell.edu (Mike Lijewski)
Newsgroups: comp.lang.fortran
Subject: passing subarrays to functions
Keywords: F77 pass by value pass by reference
Message-ID: <8378@batcomputer.tn.cornell.edu>
Date: 12 Jul 89 16:12:02 GMT
Distribution: comp
Organization: Cornell National Supercomputer Facility
Lines: 43


     Consider the following program:

      program main
      dimension a(100)
      do 10 i = 1, 100
        a(i) = 2.0
10    continue
      write(6,*) 'The sum is ', sum(a)
      write(6,*) 'The sum is ', sum(a(51))
      end

      function sum(x)
      dimension x(50)
      temp = 0.0
      do 10 i = 1, 50
        temp = temp + x(i)
10    continue
      sum = temp
      end

This produces: The sum is 100.0
               The sum is 100.0

on each of an IBM 3090 using fortvs under both CMS and fvs under
AIX, Sun 386i using SunOS f77 Version 4.0.1, and a Cray X-MP/48
using cft77 under UNICOS 4.0.8.  My understanding was that since
a(51) is a scalar it would be passed by reference and this code
wouldn't work. Apparently though, a(51) is being resolve to the
address of a(51).  to see that it does work though.  I used to think
that you needed to equivalence a(51) to another array to do this kind
of thing.  What is the official F77 word on this type of construct?


Mike Lijewski  (H)607/277-7623 (W)607/255-0539 (desk)607/255-2960
Cornell National Supercomputer Facility
ARPA: mjlx@cornellf.tn.cornell.edu  BITNET: mjlx@cornellf.bitnet
SMAIL:  102 E. Court St. Ithaca, NY  14850
-- 
Mike Lijewski  (H)607/277-7623 (W)607/255-0539 (desk)607/255-2960
Cornell National Supercomputer Facility
ARPA: mjlx@cornellf.tn.cornell.edu  BITNET: mjlx@cornellf.bitnet
SMAIL:  102 E. Court St. Ithaca, NY  14850