flook  0.7
FORTRAN wrappers for calling LUA

The fortran-Lua-hook library.

It allows abstraction of input files to be pure Lua files to enable configuration of internal variables through an embedded Lua interpreter.

Any valid Lua script can be executed from within any fortran application at points where the application creates Lua channels.

Its main usage is the ability to change run-time variables at run-time in order to optimize, or even change, the execution path of the parent program.


The API documentation of flook resides at documentation.

Imagine you have a program which has 3 distinct places where interaction might occur:

program main
call initialize()
call calculate()
call finalize()
end program

At each intermediate point one wishes to communicate with a scripting language. flook lets you communicate fortran and Lua. For an elaborate example see Examples.

Downloading and installation

Installing flook requires you to first fetch the library which is currently hosted at github at flook.

To fetch all required files do this

git clone https://github.com/ElectronicStructureLibrary/flook.git
cd flook
git submodule init
git submodule update
ls -l

At this point you should see (at least) the following directories and files:

drwxr-xr-x 7 USER GROUP 4.0K Jun  5 17:57 aotus
-rw-r--r-- 1 USER GROUP 7.5K Jun  5 17:56 LICENSE
-rw-r--r-- 1 USER GROUP  667 Jun  5 17:56 Makefile
-rw-r--r-- 1 USER GROUP  298 Jun  5 17:56 README.md
drwxr-xr-x 2 USER GROUP 4.0K Jun  5 17:56 src
drwxr-xr-x 2 USER GROUP 4.0K Jun  5 17:56 test

To compile flook you need a minimal arch.make file. The content of arch.make, which should be located in the top directory, can be this minimal content (please correct tabulators to conform to Makefile standards):

CC = gcc
FC = gfortran
    $(FC) -c $(FFLAGS) $(INC) $<
    $(FC) -c $(FFLAGS) $(INC) $<
    $(CC) -c $(CFLAGS) $(INC) $<

The is needed for internal reasons, (sorry about the quick mock-up)...

Type make and possibly make check to run the tests in the test directory.

Compiling the internal Lua package requires tweaking if you are using a different platform than linux.

PLATFORM = aix | bsd | c89 | freebsd | generic | linux | macosx | mingw | posix | solaris

where the default is linux, if using linux supplying PLATFORM to the arch.make file is unnecessary.


aotus is packaged together with Lua 5.3.0 and enables the direct compilation of Lua and the fortran bindings. However, if Lua gets updated or you wish to control your Lua environment you can use your local Lua installation.

By adding these flags to your arch.make

LUA_DIR = /path/to/lua/installation
INC += -I$(LUA_DIR)/include

an external library for the Lua environment will be used.


flook consists intrinsically of 4 libraries:

  1. Lua library (-llua),
  2. fortran to Lua interface (-lflu), see Thanks,
  3. basic fortran Lua interaction layer (-laotus), see Thanks,
  4. flook (-lflook).

However, two variants of linking is available.

Compiling for one link

flook can combine the libraries from 1. - 4. into one library.

To do this simply call make with this command

make liball

which creates libflookall.a in the top directory. With this library you only need to link to flook.

To link flook to your program the following can be used in a Makefile

FLOOK_PATH  = /path/to/flook/parent
FLOOK_LIBS  = -L$(FLOOK_PATH)/src -lflookall -ldl

For the sources that you compile you need to add to the command line, whilst for linking the program you need on the command line. Note that -ldl is a requirement for the Lua library, and per-see is more difficult to incorporate.

Direct linking

When compiling for one link does not work, the following method is less restrictive on the commands used.

In order to link to flook you can use this template (Makefile) for include statements and library linking (note that you should not switch the order of these statements):

FLOOK_PATH  = /path/to/flook/parent
FLOOK_LIBS  = -L$(FLOOK_PATH)/src -lflook
FLOOK_LIBS += -L$(FLOOK_PATH)/aotus/source -laotus
FLOOK_LIBS += -L$(FLOOK_PATH)/aotus/LuaFortran -lflu
FLOOK_LIBS += -L/path/to/lua/lib -llua -ldl

For the sources that you compile you need to add to the command line, whilst for linking the program you need on the command line.


Several examples exists in the test directory where one is shown in the following example:

The above program is a fortran program which communicates with an embedded Lua environment. It communicates with Lua 6 times and allows retrieval of elements and changing the elements at each communication point. The communicating Lua code looks like this:

Contributions, issues and bugs

I would advice any users to contribute as much feedback and/or PRs to further maintain and expand this library.

Please do not hesitate to contribute!

If you find any bugs please form a bug report/issue.

If you have a fix please consider adding a pull request.


The flook license is LGPL, please see the LICENSE file.


First, I owe Harald Klimach a big thanks for the creation of aotus for the Lua-Fortran embedment.

Second, I thank James Spencer for help regarding the aotus API.

Third, I thank ESL for hosting a workshop for me to participate and create the initial release.