FORTRAN charcter strings

Hello,

I try to use a Windows DLL with FORTRAN routines in R. All routines work fine,
except those which exchange a character variable with R.

The documentation "Writing R Extensions" says it's compiler dependent whether
character string exchange works with FORTRAN routines or not.

Why doesn't it work with every compiler?

Why should it?  Why should the designer of a Fortran compiler anticipate
that Thomas Dick would want to call subprograms from a C routine and pass
in C character strings, and then spend time writing code to meet his
wishes?

Does anyone know a FORTRAN90 compiler for windows that works?

No.  Not even the matching g77 works.  *But* translation by f2c will work.

Otherwise write a wrapper in Fortran that avoids having to pass character
variables around.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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On Thu, 21 Jun 2001 09:25:51 +0100 (BST), Prof Brian D Ripley

Otherwise write a wrapper in Fortran that avoids having to pass character
variables around.

More specifically:  Thomas needs a routine to translate R character
variables into Fortran character strings, and a routine to translate
them back.  R isn't doing anything very strange, so the first of these
is probably provided by a library routine for your compiler.  Look in
the manual under "Interfacing to C" or something similar.

To translate strings back, you need to be sure to allocate the memory
in the R memory space, using the R_alloc routine from R.dll.

I doubt if this will help him much, but maybe it'll help someone else:
The translations you are talking about go like this in Delphi:

1.  R character variables are arrays of pchar in Delphi.  Delphi knows
how to convert pchars to Delphi strings automatically.

2.  The routine Rpchar translates Delphi strings to R character
variables:

function R_alloc(n,size:integer):pchar; cdecl; external 'R.dll';

function Rpchar(s:string):pchar;
begin
  result := R_alloc(1,length(s)+1);
  strpcopy(result,s);
end;

Duncan Murdoch
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