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TPFORT.DOC
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1989-11-28
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TPFort v 1.2 - A link from Turbo Pascal to MS Fortran.
Copyright (c) 1989 D.J. Murdoch. All rights reserved.
PURPOSE
TPFort is a collection of several procedures that allow Microsoft Fortran
routines to be called from Turbo Pascal. I wrote it so that I could use the
binary-only NAG Fortran library for numerical routines in Turbo Pascal
programs, but it ended up being a general purpose linker.
PRICE
TPFort is absolutely free to use and incorporate into your own programs for
any purpose. Distribute it to anyone you like, but please don't remove my
copyright notice or modify it in any other way. Source code is available
(see below), but is not necessary to be able to use TPFort with Turbo Pascal
version 5.5.
METHOD
The Fortran routines are compiled into their own loader file which is loaded at
run time by a Turbo Pascal program, making most of the Fortran subroutines and
functions available to the Pascal program. The molasses-slow Fortran compiler
and linker need only be run once to create the loader; changes to the Pascal
part of the program don't force recompiling or re-linking of the Fortran part.
INSTRUCTIONS
There are several steps involved in preparing a Fortran routines to be called
from Turbo Pascal.
1. Preparing the Fortran Program
Write a Fortran program which includes the following declarations and a call
to CALLTP, in the following format:
EXTERNAL routine1, routine2, ..., routineX
CALL CALLTP(routine1, routine2, ..., routineX, X)
where routine1 through to routineX are the names of the Fortran routines you
wish to make available to your Turbo Pascal program, and X is an integer value
giving the number of routines being passed. The external declaration is
extremely important; if not given, Fortran will assume the routine names are
local integer or real variables, and things will get really messed up.
This loader may do anything else, such as reading data from files, allocating
space, etc. It's not all that important where the call to CALLTP takes place,
but more efficient use will be made of the program stack if the call comes
somewhere in the main program, rather than in a function or subroutine.
After this call and any other initialization necessary, the program should
exit. As this will close any open files, and I/O done while TP is active
is probably unreliable, it should complete any I/O operations before quitting,
and the routines being passed should avoid doing I/O.
Compile this routine and link it to the object file CALLTP.OBJ. Be sure to
specify to the linker that a larger than normal stack will be needed - I'd
suggest a minimum of 16K. The Turbo Pascal program will be using this stack
instead of its own much of the time, and TP makes much heavier use of the
stack than does Fortran.
Warning: Don't try running the loader program on its own, unless you avoid
executing the call to CALLTP. If TP isn't there to catch that call, you're
very likely to crash. It might be a good idea to rename the .EXE with a non-
executable extension such as .LDR just to be sure.
2. Preparing the TP dummy procedures
You need to create dummy versions of all the Fortran routines that you want to
call. They _must_ be declared as "far" routines, either through the use of
the $F+ compiler directive, or by putting them in the interface section of a
unit. I'd suggest isolating all of them into their own unit and interfacing
them.
Each of the dummy routines takes an argument list that corresponds exactly to
the argument list of the Fortran routine. By default, all Fortran arguments
are passed by reference, so these should be too, by declaring them as "var"
parameters. The following list gives corresponding types between the two
languages:
Fortran TP
INTEGER*2 integer
INTEGER*4 longint
INTEGER longint
REAL single
REAL*4 single
REAL*8 double
DOUBLE PRECISION double
CHARACTER*n array[1..n] of char
COMPLEX fort_complex8
COMPLEX*8 fort_complex8 These types will be declared in
COMPLEX*16 fort_complex16 the FortLink unit someday
LOGICAL fort_logical
EXTERNAL (special - see note below)
Note also that Fortran and TP use different conventions for the order of
indices in multi-dimensional arrays. For example, the Fortran array
REAL X(10,20,30)
would be declared as
x : array[1..30,1..20,1..10] of single;
in TP. Note also that TP (up to version 5.5, at least) has no facility for
variable dimensions on arrays: to handle an array which is declared as X(N,M)
you have to declare X as a one-dimensional array and handle the indexing
yourself.
Thus a call to the NAG matrix inversion routine F01AAF with Fortran
declaration
SUBROUTINE F01AAF(A, IA, N, UNIT, IUNIT, WKSPCE, IFAIL)
INTEGER IA, N, IUNIT, IFAIL
REAL*8 A(IA,N), UNIT(IUNIT,N), WKSPCE(N)
would be simulated with dummy declarations something like
procedure f01aaf(var a:realarray; { realarray is declared in the
FortLink unit }
var ia, n:longint;
var unit:realarray;
var iunit:longint;
var wkspce:realarray;
var ifail:longint);
and element A(I,J) would be addressed at a[i+(j-1)*ia].
The content of the dummy pascal routine is very simple, and should not be
varied. If the Fortran routine is a SUBROUTINE, use a definition like
const
f01aaf_num = 1; { this is the position of F01AAF in the call to CALLTP }
procedure f01aaf;
begin
callfort(f01aaf_num);
end;
If desired, additional instructions can be put before the call to callfort;
however, no local variables may be declared and no instructions may follow the
call.
If the Fortran routine is a FUNCTION, what to do depends on the function's
type. Fortran and TP agree on the convention for returning values up to 4
bytes (except singles/REAL*4), so callfort can be used for these functions.
The most common would be a Fortran INTEGER function being declared as a TP
longint function and using callfort.
However, Fortran and TP use different conventions for other return types, and
you need to use special calls to do the conversion. If the Fortran routine is
a REAL*8-valued FUNCTION, the "fdouble" procedure replaces callfort. Use
"fsingle" for REAL*4 values. For example, for the Gaussian random number
generator G05DDF, the Fortran declaration is
REAL*8 FUNCTION G05DDF(A, B)
REAL*8 A, B
and the Pascal declarations are
function g05ddf(var a,b:double):double;
with implementation
const g05ddf_num = 2;
function g05ddf;
begin
fdouble(g05ddf_num); { Note that this is a procedure! }
end;
Other structured types can also be returned with some care. You have to
declare the dummy function to be a pointer to the appropriate type, and use
the "fpointer(procnum)" call to the Fortran routine. TPFORT only reserves
8 bytes of space for return values, but larger values can be returned with
some trickery as described in FORTLINK.DOC in the header for fpointer.
3. Preparing the TP main program
Once you have your dummy procedure unit set up, you have to make some
modifications to the main program to link in the Fortran at run-time.
This is all done in a single call to
function loadfort(prog:string;TPentry:pointer):boolean;
The prog argument should contain a string giving the fully qualified name of
the Fortran program to be loaded; TPentry should give the address of a TP
routine taking no arguments, which is going to do all the calculations with
the Fortran routines. It's necessary to do things this way because the call
to loadfort switches over to the Fortran stack; TPentry^ and any routine it
calls must be able to execute there. If LoadFort is successful, it wo