[racket] fun porting scsh to Racket

just putting this in writing helped a lot: I'll give solution 3 a try (see below). I'd still love to pair with Racketeers, so let me know if u're interested. Unfortunately, noone here at Hacker School wants to do any Racket, everyone's hyped by Clojure, JavaScript and Python. Feeling so lonely :)  

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Anyone wants to brainstorm porting scsh to Racket? I'm having an architectural block here, would appreciate any help. 

I already have syntactic niceties of scsh transcribed into lower-level calls [github]. Deciding what those calls should be is where I'm stuck. I'll be happy to just spawn new processes and have them communicate for now. I hoped I could get away with mostly using Racket's (subprocess ..), but unfortunately it only works for invoking external stuff. So having a pipe like this won't work:

> (run 
>     ((| (ls) 
>         (begin . (some racket code here))
> 	(some other external program here))
>     (> (current-error-port) LogFile))

Notice the (begin ..) form in the middle. (subprocess ..) is a primitive written in C [thx to nice people on #racket IRC for pointing it out]. If I had primitives like fork and exec, I could just follow along the original implementation or guile-scsh. Guile has access to almost full library of Posix syscalls, which I think were written for scsh to begin with. It seems wasteful to throw away all the work in Racket's port.c that basically hides the mess of dealing with Unix fdes from you (among other things) - its 10'000 lines of C code!

Right now I have three possible solutions in mind:

1 - Racket/ffi fork and exec from the C world and follow in the footsteps of original implementation. This means writing C, messing with Racket's ffi, messing with proper treatment of Unix file-descriptors with garbage collection in mind, etc. 

2 - with above pipe example in mind wrap the (begin ...) bit in a separate thread or something, spawn external stuff through calls to (subprocess ..). Basically do some concurrency magic [again, pointed on #racket IRC].

3 - i'm overcomplicating things. Just (make-pipe) inside (begin ..) and (subprocess _ pipe-in _ ..) the next external process.

I'm in EST timezone, so can pair with anyone in US (skype, facetime, ...), unless you find it weird, in which case email or IRC me. 

---
Vlad Kozin <vladilen.kozin at gmail.com>



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