Q about interrupt and catch

Q about interrupt and catch

[Mike Gran]

Hi all,

This is probably a simple question, but, I can't figure it out.

I have a program with a big main loop like this

(while #t
 (let ((c (read-char port)))
   (cond
    ... many different possible operations, depending on c
    )))

I want to make it so, when the program receives a SIGINT, it aborts
the operation in progress and restarts this big main loop.

Any hints?

Thanks,
Mike Gran

Re: Q about interrupt and catch

[Thien-Thi Nguyen]

[-- Attachment #1.1: Type: text/plain, Size: 275 bytes --]


() "Mike Gran" <spk121@yahoo.com>
() Sun, 11 Jun 2017 10:50:49 -0700

   I want to make it so, when the program receives a SIGINT, it
   aborts the operation in progress and restarts this big main
   loop.

Use ‘sigaction’ and a periodic check.  For example:


[-- Attachment #1.2: foo --]
[-- Type: application/x-scheme, Size: 733 bytes --]

[-- Attachment #1.3: Type: text/plain, Size: 438 bytes --]


This does not restart the big main loop, but it does show how to
integrate ‘sigaction’ into normal control flow.  Mod to taste...

-- 
Thien-Thi Nguyen -----------------------------------------------
 (defun responsep (query)
   (pcase (context query)
     (`(technical ,ml) (correctp ml))
     ...))                              748E A0E8 1CB8 A748 9BFA
--------------------------------------- 6CE4 6703 2224 4C80 7502


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 197 bytes --]

Re: Q about interrupt and catch

[Alex Vong]

[-- Attachment #1.1: Type: text/plain, Size: 717 bytes --]

"Mike Gran" <spk121@yahoo.com> writes:

> Hi all,
>
> This is probably a simple question, but, I can't figure it out.
>
> I have a program with a big main loop like this
>
> (while #t
>  (let ((c (read-char port)))
>    (cond
>     ... many different possible operations, depending on c
>     )))
>
> I want to make it so, when the program receives a SIGINT, it aborts
> the operation in progress and restarts this big main loop.
>
> Any hints?
>
> Thanks,
> Mike Gran

This is an interesting question. I come up with a solution using the
reset/shift operators. This is the first time I use delimited
continuation. The script is in the attachment. You can run
'chmod +x main-loop.scm' to make the script executable.


[-- Attachment #1.2: main-loop.scm --]
[-- Type: application/octet-stream, Size: 438 bytes --]

#!/bin/sh
#!/usr/bin/guile -*- Scheme -*-
# ; Portability hack to find an interpreter and get Emacs in the right mode.
exec guile -e main "$0"
!#

(use-modules (ice-9 control))

(define (main-loop)
  (let ((c (read-char)))
    (if (not (eof-object? c))
        (write-char c))
    (main-loop)))

(define main
  (lambda _
    (reset (sigaction SIGINT
             (lambda _
               (shift _ (main-loop))))
           (main-loop))))

[-- Attachment #1.3: Type: text/plain, Size: 14 bytes --]


Cheers,
Alex

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]