fisl

commit 3e6652310186a1debf0710fa1d071a4a7c876deb (patch)
parent 517e4a7c97715986f72c5902c8162b95b9c21c5b
Author: Alex Karle <alex@alexkarle.com>
Date:   Tue,  8 Nov 2022 23:14:50 -0500

repl: Add threads and nrepl for live image updates

This was a deep rabbit hole, mostly because (read-line) is blocking I/O
and _all_ threads block when blocking I/O is hit (except tcp). This was
counterintuitive (isn't the whole point of threads to swap when on I/O?)
but nevertheless, I got it to work!

Here's my setup:

1. Start the CHICKEN interpreter via the executable (drops into Lox
   interpreter):

$ ./fisl.scm
> print 1 + 1;
2
>

2. In another tmux split, create a fifo and connect to the 1234 nrepl
   port (credit: http://www.foldling.org/hacking.html#2012-08-05):

$ mkfifo repl
$ cat > repl & nc localhost 1234 < repl

3. Lastly, in Vim, run the following to send the current paragraph to
   the repl on C-c C-c:

:nnoremap <C-c><C-c> vap:w >> repl<CR>

---

Demo:

* Go to (prompt), update s/display "> "/display ">> "/
* C-c C-c
* Hit enter in fisl -- notice prompt is changed!

Diffstat:
M
fisl.scm
 | 
35
++++++++++++++++++++++++++---------

1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/fisl.scm b/fisl.scm
@@ -1,6 +1,9 @@
 #!/usr/local/bin/chicken-csi -ss
 ;; fisl -- fisl is scheme lox
-(import (chicken io)
+(import srfi-18
+        nrepl
+        (chicken io)
+        (chicken repl)
         (chicken base)
         (chicken format))
 
@@ -16,14 +19,25 @@
 	  (if stmts
 	      (interpret stmts))))))
 
-(define (run-prompt)
+(define (prompt)
+  ;; HACK: srfi-18 blocks for IO, so having run-prompt
+  ;; use read-line means that nrepl just doesn't work :(
+  ;; the "solution" is to set the i/o to non-blocking
+  ;; (adapted from the srfi-18 egg itself)
   (display "> ")
-  (let ((l (read-line)))
-    (if (not (or (eof-object? l) (equal? l ",q")))
-      (begin
-        (run l "repl")
-        (clear-err!)
-        (run-prompt)))))
+  (flush-output)
+  (##sys#thread-block-for-i/o! ##sys#current-thread 0 #:input)
+  (thread-yield!))
+
+(define (run-prompt)
+  (parameterize ((repl-prompt "> "))
+    (prompt)
+    (let ((l (read-line)))
+      (if (not (or (eof-object? l) (equal? l ",q")))
+        (begin
+          (run l "repl")
+          (clear-err!)
+          (run-prompt))))))
 
 (define (run-file fname)
   (call-with-input-file fname (lambda (p)
@@ -33,6 +47,9 @@
 (define (main args)
   (let ((argc (length args)))
     (cond
-      ((eq? argc 0) (run-prompt) (exit 0))
+      ((eq? argc 0)
+       (thread-start! (lambda () (run-prompt) (exit 0)))
+       (print "starting the repl")
+       (nrepl 1234))
       ((eq? argc 1) (run-file (car args)))
       (else (die "Too many arguments. Usage: fisl [FILE]")))))