From help-octave-request at bevo dot che dot wisc dot edu  Tue May 15 09:50:13 2001
Subject: Re: Fortran
From: Przemek Klosowski <przemek at jazz dot ncnr dot nist dot gov>
To: sgroi at ch dot unito dot it, help-octave@bevo.che.wisc.edu
Date: Tue, 15 May 2001 10:50:12 -0400


   How can I dinamically link my FORTRAN functions with Octave? In the manual only a
   C++ function is described and I don't know how to write a C++ wrapper
   funtion (because I don't know C++....).

You can pretty much write C in a C++ file. Take a template of an
octave external C++ function (there's a short example 'oregonator.cc')
in the octave source distribution, and change it for your needs. It
is compiled with the command 'mkoctfile' which is also provided w/octave.

 Linking FORTRAN to octave may vary depending on your platform; different
compilers use different conventions for passing parameters and results.
It's not difficult, just tedious:

	- all parameters are passed to and from FORTRAN by reference,
          and need to be declared as pointers in C/C++          

	- Fortran may prepend or append underscores to function names;
          You can check it by compiling a FORTRAN routine and looking
          for symbols  it defines:

		cat a.f
		      subroutine a
		      end
      
                g77 -Wall -c a.f
                nm a.o
                 00000000 T a_              <--- G77 appends underscores
                 00000000 t gcc2_compiled.

	- fortran strings might be passed funny: g77 uses the convention
	  of passing by reference, and appending an integer argument holding
	  the length of the string (passed BY VALUE) to the end of FORTRAN 
          argument list. The above is from memory--I might have gotten the
          details slightly wrong.

Perhaps Octave has some mechanism that takes care of some of these details---
I haven't needed FORTRAN in a while. Can anyone help?


	przemek



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