cffi VS polymorphic-functions

When you want to do anything that breaks the nice bubble of your Lisp image, you might want to know a bit about your operating system's programming interface. This will come in handy if you ever need to wrap a library with CFFI. There are some things that are pretty inconvenient as a rule (like dealing with any protocol that uses network byte order), but if you stay within the bubble of your Lisp image, you won't really notice them.

I'm just posting the work that I have done over the last year or so on CL-Objc. I'm still blocked from better support (e.g., passing structs by value for frameworks like UIKit). I just wanted to post what I have done online for others interested in the work or motivated to collaborate on this.

Good morning ladies and gentlemen, I have been waiting on some feedback for PR in CFFI. This feature is blocking me from reviving CL-OBJC. Any help will be appreciated. Thank you in advance.

Is that actually https://github.com/cffi/cffi/commit/33970351e71bb5f12ba56fc40270089e948ae112 ? I.e. after loading cl+ssl. (Although Hunchentoot does not interrupt threads)

Maybe access the pins using CFFI, https://github.com/cffi/cffi package and one the libraries mentioned here? https://www.bigmessowires.com/2018/05/26/raspberry-pi-gpio-programming-in-c/

FTR, on my system QL fetches CFFI 0.23.0 and the fix/error I'm talking about is https://github.com/cffi/cffi/blob/master/src/libraries.lisp#L106 and seems to have been added iin this PR https://github.com/cffi/cffi/pull/173/commits/263b38f4f2600dbacde8f2b313620c35a563c6df so the fix should be in CFFI 0.24.0 released 24 March 2021.

FTR: this is the PR https://github.com/cffi/cffi/pull/173/commits/263b38f4f2600dbacde8f2b313620c35a563c6df

C: Alternatively (more difficult) you could try to wrap the underlying C layers of either of those mentioned under Python with CFFI. The C-based game engine, Raylib, is also wrappable this way. I finished a super cool walking simulator in CL with that, but it is more tedious than the others since raylib is really barebones.

I feel inspired to start Lisp after being disappointed with the "open" source scene of 2021. I'd rather pay LispWorks a yearly fee and be left alone than dealing with unbalanced people in the Python space. The free Lisp implementations also look somewhat isolated from the ideological wars.

However, a C interface is required. Is this one the recommended solution? Is it really portable?

https://common-lisp.net/project/cffi/

What is the speed compared to a Python C extension? Are implementation-specific C interfaces faster (I guess they are)?

Sorry for so many questions, but these can usually only be answered by people who have actually used the interface.

If performance is a concern, then you would want to stick to CLHS provided simple-array and create appropriate types using deftype, and then dispatch on the types either by yourself, or by using something like polymorphic-functions and polymorph.maths.

If you want to dispatch on vectors, you can try out polymorphic-functions which was made for the express purpose of dispatching on specialized arrays aka types rather than classes.

Since the past year or two, I have been working on numericals that aims to provide the speed of NumPy with the goodness of Common Lisp. In particular, this includes the use of dynamic variables, restarts, and compiler-notes wherever appropriate. It uses CLTL2 API (and may be slightly more) under the hood to provide AOT dispatch, but nothing stops you from combining it with JAOT dispatch provided by numcl/specialized-function. This also spawned a number of projects most notably polymorphic-functions to dispatch on types instead of classes and extensible-compound-types that allows one to define user defined compound types (beyond just the type-aliases enabled by deftype. Fortunately enough, interoperation between magicl, numcl and numericals/dense-numericals actually looks plausible!

Before reading this, please go and check out https://github.com/digikar99/polymorphic-functions which this project is fully based on. It's great.

What I am calling parametric polymorphism is this test: