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https://github.com/interkosmos/fortran-tcl86

Fortran 2018 interface bindings to Tcl/Tk 8.6
https://github.com/interkosmos/fortran-tcl86

fortran fortran-2018 fortran-package-manager fpm tcl tcl-tk tk

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Fortran 2018 interface bindings to Tcl/Tk 8.6

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# fortran-tcl86 – Tcl/Tk 8.6 for Fortran 2018

A work-in-progress Fortran 2018 ISO_C_BINDING interface library for

interoperability with Tcl/Tk 8.6. This library allows you



* to embed Tcl into Fortran,

* to create Tcl extensions in Fortran (with Tcl Stubs),

* to access (a subset of) the Tcl/Tk C API from Fortran,

* to use Tcl as an evaluatable configuration file format, and

* to add graphical user interfaces to Fortran programs.



There are some smaller differences to the original API:



* Procedure names have been converted from camel case to snake case (for

  example, `tcl_eval_ex()` in Fortran instead of `Tcl_EvalEx()` in C).

* Character strings passed to library procedures do not have to be

  null-terminated, as this step is done by Fortran wrappers.

* Types are converted to their Fortran counter-parts (such as `logical` instead

  of `c_int` for boolean values).

* Some procedure arguments have been made optional to avoid passing of

  `c_null_ptr`, `c_null_funptr`, and `0`.

* The interfaces called by the wrapper procedures contain a trailing underscore

  `_` in their name (for example, wrapper `tcl_eval()` appends a null character

  to the second argument, then calls Fortran interface `tcl_eval_()`).

* Functions and routines exposed to Tcl must have the `bind(c)` attribute.



See [COVERAGE](COVERAGE.md) for a table of the bound procedures.



## Fortran Libraries

| Library           | Description                                                      |

|-------------------|------------------------------------------------------------------|

| `libftcl86.a`     | Bindings to Tcl (`libtcl86`)                                     |

| `libftclstub86.a` | Bindings to Tcl Stubs for extensions in Fortran (`libtclstub86`) |

| `libftk86.a`      | Bindings to Tk (`libtk86`)                                       |



## Build Instructions

Tcl 8.6 and Tk 8.6 with development headers have to be present. On FreeBSD,

install the packages with:



```

# pkg install lang/tcl86 x11-toolkits/tk86

```



You will also need a Fortran 2018 and a C compiler. Then, execute the provided

`Makefile` to build the static Fortran interface libraries `libftcl86.a`,

`libftclstub86.a`, and `libftk86.a`:



```

$ make

```



By default, `gcc` and `gfortran` are used for compilation, but you can override

the settings:



```

$ make CC=icc FC=ifort

```



Furthermore, it is possible to build a single static library `libfortran-tcl86.a`

with [fpm](https://github.com/fortran-lang/fpm):



```

$ fpm build --profile=release --c-flag="`pkg-config --cflags tcl86`"

```



The include and library search paths in `--c-flags` have to point to the correct

directories.



## Linking Tcl & Tk

Linking depends on whether Fortran is called from Tcl or Tcl from Fortran.  To

build a Fortran program in `example.f90` that invokes the Tcl interpreter, link

against `libftcl86.a -ltcl86`:



```

$ gfortran -I/usr/local/include/tcl8.6/ -L/usr/local/lib/tcl8.6/ \

  -o example example.f90 libftcl86.a -ltcl86

$ ./example

```



The include and library search paths as well as the name of the Tcl 8.6 library

itself may have to be changed depending on your operating system (`-ltcl8.6`

instead of `-ltcl86` on Linux). Tcl/Tk can either be linked statically

(`libtcl86.a`, `libtk86.a`) or dynamically (`-ltcl86`, `-ltk86`).



To create a shared library `libexample.so` with Tcl extensions written in

Fortran, run:



```

$ gfortran -DUSE_TCL_STUBS -fPIC -shared -o libexample.so `pkg-config --cflags tcl86` \

  example.f90 libftcl86.a libftclstub86.a `pkg-config --libs tcl86`

```



To access the Tk toolkit from Fortran, link against `libftk86.a libftcl86.a

-ltk86 -ltcl86` (or, use `pkg-config`):



```

$ gfortran -DUSE_TK_STUBS `pkg-config --cflags tk86` \

  -o example example.f90 libftk86.a libftcl86.a `pkg-config --libs tk86`

$ ./example

```



## Example

The following basic example just invokes the Tcl interpreter from Fortran to

evaluate a character string:



```fortran

! example.f90

program main

    use, intrinsic :: iso_c_binding, only: c_associated, c_ptr

    use :: tcl

    implicit none (type, external)



    integer     :: rc

    type(c_ptr) :: interp



    ! Create Tcl interpreter.

    interp = tcl_create_interp()

    if (.not. c_associated(interp)) stop 'Error: Tcl_CreateInterp() failed'



    ! Evaluate string as Tcl command.

    rc = tcl_eval_ex(interp, 'puts "Hello, from Tcl!"')

    if (rc /= TCL_OK) print '("Error: Tcl_EvalEx() failed")'



    ! Delete Tcl interpreter.

    call tcl_delete_interp(interp)

end program main

```



Compile and link the example with:



```

$ gfortran `pkg-config --cflags tcl86` -o example.f90 libftcl86.a `pkg-config --libs tcl86`

$ ./example

Hello, from Tcl!

```



## Further Examples

The following example programs are provided:



* **config** – Uses Tcl as a configuration file format (run `config`).

* **dict** – Shows dictionary access (run `dict`).

* **eval** – Evaluates a script in the Tcl interpreter (run `eval`).

* **fs** – Tests Tcl file system API procedures (run `fs`).

* **library** – Creates a Tcl extension `hello` inside a shared library (run `script.tcl`).

* **link** – Demonstrates shared access to a variable between Tcl and Fortran (run `link`).

* **namespace** – Creates a Tcl extension `::fortran::hello` (with namespace) inside a shared library (run `script.tcl`).

* **re2c** – Shows a Tk window to convert temperature values by calling an extension written in Fortran (run `re2c`).



To build the examples, run:



```

$ make examples

```



Change to the directory of an example before executing it.



## Licence

ISC