Welcome to f2cl - a Fortran to Common Lisp Translator

Contained in this directory are source code files and some documentation.
The translator is written in Common Lisp making installation simple.

Installation

If this has been extracted as a part of CLOCC, the way to build f2cl
is to simply run “make system” from a shell, as is usual with CLOCC
packages.

A second method is to use defsystem (from CLOCC). Then load
f2cl.system, and then finally run (mk:oos "f2cl" :compile).

A third method is to use asdf. You can load f2cl.asd and run
(asdf:oos 'asdf:load-op :f2cl). (Asdf may not be able to find
f2cl.asd. In this case, you need to tell asdf where to find it.
The old-style is to do something like

(push "path-to-directory" asdf:*central-registry*)

where “path-to-directory” is the path to the directory containing
“f2cl.asd”.

Finally, a fourth method, if you have none of the above, is to
manually run everything as follows:

Start your favorite Common Lisp implementation use the function
compile-file to compile each of the source files:

 f2cl-package.lisp
 f2cl1.lisp
 f2cl2.lisp
 f2cl3.lisp
 f2cl4.lisp
 f2cl5.lisp
 f2cl6.lisp
 f2cl7.lisp
 f2cl-lib.lisp

Load up all of the files

 (load "f2cl-package.lisp")
 (load "f2cl1.lisp")
 (load "f2cl2.lisp")
 (load "f2cl3.lisp")
 (load "f2cl4.lisp")
 (load "f2cl5.lisp")
 (load "f2cl6.lisp")
 (load "f2cl7.lisp")
 (load "f2cl-lib.lisp")

to load all the compiled files.

Usage

Converting Fortran Code

To use f2cl:

(f2cl:f2cl "<path>/fortran.f")

will convert the file <path>/fortran.f to Lisp code and places the
result in the file <path>/fortran.lisp.

Alternatively,

(f2cl:f2cl-compile "<path>/fortran.f")

will also run compile-file on the Lisp file so you can load it
directly into your lisp.

For those anxious to use the translator without studying the documentation
here is a short list of restrictions that may result in obscure errors:

input code is assumed to be valid Fortran 77
no tabs are permitted in the source,
$comments should only be turned on if the Fortran code has comments
exclusively within subroutines,
linebreaks must occur within whitespace,
spaces are required to separate symbols.

Note also that an intermediate file called “prep.tmp” is produced by the
preprocessing stage of the translation.

Options

These are the options available to f2cl:f2cl and f2cl:f2cl-compile

:OUTPUT-FILE
File to contain Lisp code
:VERBOSE
Verbose output. Default = NIL. Mostly for debugging.
:PRUNE-LABELS
Prune unused labels. Default = NIL.
:INCLUDE-COMMENTS
Include Fortran comments in the Lisp output.
```
  Default = NIL
```
:AUTO-SAVE
Variables in DATA statements are automatically SAVE’d. Default
= T.

:RELAXED-ARRAY-DECLS
Declarations of array sizes are relaxed in formal

  parameters to functions. That is, any array
  length declarations (except lower limits) are
  ignored if possible, like old Fortran used
  to. Default = T.

:COERCE-ASSIGNS
If T or :ALWAYS, all assignment statements automatically

  coerce the RHS to the appropriate type for the assignment.  If
  `NIL` or `:NEVER`, coercion never happens.  If `:AS-NEEDED`, f2cl
  applies coercion if it thinks it is needed.  Default =
  `:AS-NEEDED`.

:EXTENSION
The extension to use for the output file, if needed. Defaults
```
  to `*DEFAULT-LISP-EXTENSION*` or "lisp".
```
:KEEP-TEMP-FILE
If T, the temporary file is not deleted. This is mostly for
debugging f2cl. Default = NIL.

:ARRAY-TYPE
The type of array f2cl should use. Should be :simple-array or

  `:array`.  For some compilers, there can be significant speed up
  if the array can be declared as simple-arrays.  But this is
  incompatible with array-slicing, so care must be used if you
  choose `:simple-array`. Default = `:array.`

:ARRAY-SLICING
When non-NIL, f2cl assumes that, whenever we do an array

  reference in a call to a subroutine or function, we are really
  passing a subarray to the routine instead of just the single
  value, unless f2cl knows the function takes a scalar arg that
  is not modified.  Default = `T`.

:PACKAGE
A string or symbol specifying what package the resulting code

  should be in. (Basically puts a `(in-package <p>)` at the top.)
  Default is "COMMON-LISP-USER".

:DECLAIM
Declaim compilation options (Basically puts a (declaim <declaim>) at the top.) Default is none.

:DECLARE-COMMON
When non-NIL, any structures definitions for common blocks are

  defined when converting this file. Otherwise, the structures
  for the common blocks are expected to be defined elsewhere.
  This should be used only once for one subprogram that will be
  used to define the common block.  See below for more
  information. Default is `NIL`.

:FLOAT-FORMAT
Float format to use when printing the result. Default is
```
  `*READ-DEFAULT-FLOAT-FORMAT*`
```
:COMMON-AS-ARRAY
Instead of defining a common block as a structure with the
same slot names as variables in the common block, the common
block is defined as a set of arrays. The actual common block
variables are defined as offsets into these arrays. For more
information see below. This mimics the memory layout of how
Fortran treats common blocks. Default = NIL.

Using Converted Code

Once you’ve converted the code, you do not need to load up all of f2cl
to use the converted code. In fact, you only need f2cl0.l and
macros.l to define the necessary packages and functions used by the
converted code. Actually, you really only need the defpackage for
f2cl-lib in f2cl0.l.

Issues

For a more detailed list of issues and notes, see src/NOTES.

We highlight just a few issues here.

Block data statements

In Fortran, block data statments are used to initialize common
blocks. Since Fortran executables are loaded and run just once,
this is not a problem. However, in Lisp, this might not be true,
and you may want to run the main program many times. Thus, it is
up to you to run the block data initializer at the right time, as
needed. f2cl cannot know when and where to call the initializer.

Common blocks

F2cl converts common blocks to structures. However, common blocks
may be referenced in several different files, so the user must
tell f2cl when to define the structure. Use the :declare-common
parameter to tell f2cl to define the structure. This should be
done exactly once for each common block that is defined. This
should also be done for the first file that is compiled and
loaded, so that subsequent files know about the definition.

In addition, there is another option, :common-as-array. This
changes how f2cl handles common blocks. A rather common use of
common blocks has the same common block using different variable
names. For example, one routine might have

        COMMON /foo/ a(10), b, i(4)

and another might say

        COMMON /foo/ b(9), c, d, j(2), k(2)

In Fortran, this is perfectly acceptable. Normally, f2cl expects
all common blocks to use the same variable names, and then f2cl
creates a structure for the common block using the variable names
as the names of the slots. However, for a case like the above,
f2cl gets confused. Hence, :common-as-array. We treat the common
block as an array of memory. So this gets converted into a
structure somewhat like

        (defstruct foo
          (part-0 (make-array 11 :element-type 'real))
          (part-1 (make-array 4 :element-type 'integer4)))

(In a more general case, we group all contiguous variables of the
same type into one array. f2cl and Lisp cannot handle the case
where a real and integer value are allocated to the same piece of
memory.)

Then in the individual routines, symbol-macrolets are used to
create accessors for the various definitions. Hence, for the
second version, we would do something like

          (symbol-macrolet 
            (b (make-array 9 :displaced-to 
                           (foo-part-0 *foo*)
                           :diplaced-offset 0))
            (c (aref (foo-part-0 *foo*) 9))
            (d (aref (foo-part-0 *foo*) 10))
            (j (make-array 2 :displaced-to
                           (foo-part-1 *foo*)
                           :displaced-offset 0))
            (k (make-array 2 :displaced-to
                           (foo-part-1 *foo*)
                           :displaced-offset 2))
            ...)

Thus, we access the right parts of the common block, independent
of the name. Note that this has a performance impact since we
used displaced arrays.

Conversion order

While not necessary, f2cl can do a significantly better job in
generating code if the functions are compiled in the correct
order. This means any function, F, that is called by another
function, G, should compiled first. In this way, f2cl can
determine the calling conventions for F, and generate the
appropriate call for F in G. This is important if F takes an
array argument and G passes a slice of an array to F, or
conversely if F takes a simple variable, and G calls F with an
array reference.

If this is not done, the user may have to modify either the
Fortran code or the resulting Lisp code to pass arguments
correctly.

F2cl cannot always determine whether a slice of an array should be
used or just the single element.

See also the file src/NOTES which contains a change log. But there
are also various notes about about restrictions and enhancements on
various features supported by f2cl.

Acknowledgments

The translator was written by Kevin Broughan and Diane Koorey Willcock
at the University of Waikato. Reports should be sent to
kab@waikato.ac.nz and should include examples of Fortran code which
fails to translate or which translates incorrectly.

Major changes have be written by Raymond Toy and the entire translator
is now part of CLOCC, with permission from Kevin Broughan. Send bug
reports and other comments to http://clocc.sourceforge.net.

The code is also placed under the GPL, by permission of Kevin
Broughan. The exception is macros.l which is released under the LGPL
so that it can be incorporated into other packages.