NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/lang/c/20092

Internet Message Format | 1993-01-23 | 3.3 KB

Xref: sparky comp.lang.c:20092 comp.lang.fortran:5136
Newsgroups: comp.lang.c,comp.lang.fortran
Path: sparky!uunet!cs.utexas.edu!hermes.chpc.utexas.edu!michael
From: [e-mail] (Michael Lemke)
Subject: Re: calling a Fortran subroutine from a C program
Message-ID: <[e-mail]>
Organization: The University of Texas System - CHPC
References: <[e-mail]> <[e-mail]>
Date: Fri, 22 Jan 93 23:36:18 GMT
Lines: 63

In article <[e-mail]> [e-mail] (Bob Pitha) writes:
>Michael Lemke ([e-mail]) wrote:
>: In article <[e-mail]> [e-mail] (Bob Pitha) writes:
>   (edited a bit for brevity's sake)
>: >
>: >4) Character arrays: For each character array in the argument list, there
>:               ^^^^^^
>
>: You are not talking about character arrays at all in your post.  A
>: character array is something you declare as
>
>:     character*(*) string(10)
>
>: which is an array of strings.  You talked just about plain character
>: strings.  Keep the terms clear.  Passing of character arrays is a bit
>: harder than what you described I believe (I might be wrong) but I don't
>: have my Sun manual handy to point out the differences.  Someone else
>: might.  But as you have suggested (which I deleted for brevity) reading
>: the Sun Fortran manual is worth doing.  It deals with all these issues.
>
>  This is really just an issue of semantics, but you're right that I wasn't
                          ^^^^^^^^^^^^^^^^^^

Not quite.  To make it really clear:  The difference is

    CHARACTER*100 STRING

or

    CHARACTER*1 STRING(100)

which are very different data structures.   The latter is an array, the
first is a single variable.  I don't care how C chews its memory, it can
hardly distinguish these two cases.  The last is pretty close in
functionality to C's concept (except for having a length stored
somewhere) as you'd need something like strcpy to copy data.

>very clear.  I was thinking in terms of an "array of type char" in C, so
>I just wrote what I was thinking.  As you point out, to a person who only
>knows Fortran the phrase "character array" may by misleading.  Unfortunately,
>this is an area where the concepts don't map well between the two worlds,
>since c doesn't have an official "string" type; a string is just a null-
>terminated array of characters.
>
>  Passing "arrays of strings" (is that clear enough?) is perhaps a little
>bit harder, but not a whole lot.  I didn't touch on null-termination and
>blank-filling in my previous post because I didn't know whether the
>original questioner cared and it would have taken lots more space.  I
>stuck to the simple case of passing an array of characters to the Fortran
>routine.  If the Fortran routine were going to try to pass a string back
>to C, or if an array of strings were being passed, you have to deal with
>these issues.
>
>-----------------------------------------------------------------------
>Bob Pitha                      Molecular Simulations Inc.
>[e-mail]                   16 New England Executive Park
>[phone] x242            Burlington, MA 01803-5297


--
Michael Lemke
Astronomy, UT Austin, Texas
([e-mail] or UTSPAN::UTADNX::IO::MICHAEL [SPAN])