nikodemus

---
First 'scripting' excursion in Foolang!

Input is file containing stuff like this:

    CLOSURE 1:
    args: ["out"]
    body:
        (self
             displayOn: out)

nikodemus

;;;; In response to:
;;;;
;;;;    http://www.reddit.com/r/lisp/comments/3710zq/directed_procrastination_backtracking_with_the/
;;;;    http://directed-procrastination.blogspot.se/2011/05/backtracking-with-common-lisp-condition.html
;;;;
;;;; Demonstrating why one should not use conditions for this kind of stuff,
;;;; instead using the dynamic binding and unwinding facilities on which the
;;;; condition system is built. The author's backtracking system doesn't compare
;;;; badly to Screamer because his is simple: it compares badly because using
;;;; conditions is a bad match for the task.

nikodemus

;;;; By Nikodemus Siivola <[email protected]>, 2012.
;;;;
;;;; Permission is hereby granted, free of charge, to any person
;;;; obtaining a copy of this software and associated documentation files
;;;; (the "Software"), to deal in the Software without restriction,
;;;; including without limitation the rights to use, copy, modify, merge,
;;;; publish, distribute, sublicense, and/or sell copies of the Software,
;;;; and to permit persons to whom the Software is furnished to do so,
;;;; subject to the following conditions:
;;;;

nikodemus

(defconstant +foo-count+ (ash (sb-int:power-of-two-ceiling
                               (* 8 sb-vm::*backend-page-bytes*))
                              -1))

(defconstant +foo-mask+ (1- +foo-count+))

(defun foo-duplicates (list)
  (let ((bitmap (make-array +foo-count+ :element-type 'bit))
        (results nil))
    (declare (dynamic-extent bitmap))

nikodemus

;;; If a fasl was stale, try to recompile and load (once).
(defmethod asdf:perform :around ((o asdf:load-op)
                                 (c asdf:cl-source-file))
  (handler-case (call-next-method o c)
    (sb-ext:invalid-fasl ()
      (asdf:perform (make-instance 'asdf:compile-op) c)
      (call-next-method))))

nikodemus

;;;; Inspired by http://directed-procrastination.blogspot.com/2011/11/broken-weight-problem.html
;;;;
;;;; An example of using a generator to make your nondeterminism read nice.

(in-package :screamer-user)

(defun a-subset (set)
  "Non-deterministically returns all the subsets of SET, including the empty set NIL."
  (when set
    (either

nikodemus

(with-lock (*lock*)
  (unwind-protect
        ;; Calls CONDITION-WAIT on the lock
        (foo)
    ;; If FOO unwinds, the lock it might not be held here!
    (bar)))

nikodemus

(defun condition-wait (waitqueue lock &key timeout)
  (release-lock lock)
  (let ((self *current-thread*))
    (unwind-protect
        (progn
          (enqueue self waitqueue)
          (when (wait-for (eq self (queue-first waitqueue))
                          :timeout timeout)
            (grab-lock lock :timeout timeout)))
     (delete-from-queue self))))

nikodemus

Context from IRC logs for future reference.

[12:36]  <kushal> nikodemus, can you point me to some tutorial on debugging on sbcl ?
[12:37]  * andreer ([email protected]) has joined #quicklisp
[12:38]  <nikodemus> kushal: no really good ones actually exist at the moment. i'm planning on writing one before the year is out, but... in the meanwhile, i can give some pointers
[12:38]  <nikodemus> a couple of questions: is this a general question, or do you have a specific issue you need to debug?
[12:39]  <kushal> right now , general, managed to debug the specific issue somehow :)
[12:39]  <nikodemus> ok. are you using slime?
[12:39]  <kushal> nikodemus, yes and no both
[12:40]  <nikodemus> good. :)