# Portable Foreign Function Interface for R7RS schemes

Foreign function interface that is supported on multiple R7RS Sceheme implementations.

Note that this software is in **alpha** stage. That said the interface should not be changing anymore.

Any help in form of constructive advice and bug reports are appreciated.

[Documentation](https://retropikzel.neocities.org/r7rs-pffi/) or run mkdocs serve or see docs/.

[Issue tracker](https://todo.sr.ht/~retropikzel/r7rs-pffi)

[Maling lists](https://sr.ht/~retropikzel/r7rs-pffi/lists)

For documentation see [retropikzel.neocities.org/r7rs-pffi](retropikzel.neocities.org/r7rs-pffi)
or run mkdocs serve or see or docs/ directory.

# Goals

- Support only R7RS implementations
  - Needs to have cond-expand and library support atleast (propably much more)
- Same interface on all implementations
  - Some things that are procedures on one implementation are macros on other,
  but they must behave the same

# Non goals

- To support all R7RS implementations
- To have every possible FFI feature
- Compiling of C code at any point
    - That is no stubs, no C code generated by the library and so on

# Support tiers

## Tier 1

- [Chicken](https://www.call-cc.org/)
    - Still needs work
- [Guile](https://www.gnu.org/software/guile/)
    - Good support, recommended
- [Kawa](https://www.gnu.org/software/kawa/index.html)
    - Needs at least java version 22
    - Needs jvm flags:
        - --add-exports java.base/jdk.internal.foreign.abi=ALL-UNNAMED
        - --add-exports java.base/jdk.internal.foreign.layout=ALL-UNNAMED
        - --add-exports java.base/jdk.internal.foreign=ALL-UNNAMED
        - --enable-native-access=ALL-UNNAMED
    - Good support (otherwise), recommended
- [Sagittarius](https://bitbucket.org/ktakashi/sagittarius-scheme/wiki/Home)
    - Good support, recommended
- [Racket](https://racket-lang.org/)
    - Good support, recommended
- [Gambit](https://gambitscheme.org)
    - Still needs work

## Tier 2

These implementations do not have callback support on their FFI. If I'm wrong please let me know!

- [STKlos](https://stklos.net/)
    - Still needs work
- [Cyclone](https://justinethier.github.io/cyclone/)
    - Still needs work

## Tier 3

Support waiting for the implementation.

- [LIPS](https://lips.js.org/)
    - Waiting for implementation to have cond-expand and library support
    - Will only work on nodejs
- [Biwascheme](https://www.biwascheme.org/)
    - Waiting for implementation to have cond-expand and library support
    - Will only work on nodejs

## Tier 4

Support needs to be investigated.

- [Gerbil](https://cons.io/)
- [Ypsilon](http://www.littlewingpinball.com/doc/en/ypsilon/)
- [Larceny](https://larcenists.org/)
- [Mosh](https://mosh.monaos.org)
- [Skint](https://github.com/false-schemers/skint)

## Tier 5

Support maybe possible/dreaming about.

- [Airship](https://gitlab.com/mbabich/airship-scheme)
- [Other gambit targets](https://gambitscheme.org/)
  - Gambit compiles to different targets other than C too, for example Javascript. It would be cool
  and interesting to see if this FFI could also support some of those

## Tier 6

Not supported currently, and may never be.

- [Chibi](https://synthcode.com/scheme/chibi)
    - FFI requires C code
- [MIT-Scheme](https://www.gnu.org/software/mit-scheme/)
    - FFI requires C code
- [tr7](https://gitlab.com/jobol/tr7)
    - FFI requires C code
- [Gauche](https://practical-scheme.net/gauche/)
    - FFI requires C code
- [s7](https://scheme.fail://ccrma.stanford.edu/software/snd/snd/s7.html)
    - No library support
    - Might have other things missing too
- [Loko](https://scheme.fail/)
    - Desires no C interop, I can respect that