Share uninterned symbols in *print-circle*

[Affonso-Gui]

Makes (let ((g (gensym))) (list g g)) print as (#1=#:G824 #1#), when *print-circle* is non-nil. Since this is a dumpable and loadable form, #266 gets solved. (It is also default behavior in clisp and sbcl.)

Can be tested with below code:

(let ((lst (let ((g (gensym))) (list g g)))
      (*print-circle* t))
  (assert
   (reduce #'eq (read-from-string (format nil "~S" lst)))
   "Unable to read uninterned symbol"))

[k-okada]

please use `restart travis euslisp/EusLisp 709.9`

…

-- ◉ Kei Okada 2018-04-03 9:39 GMT+09:00 Affonso, Guilherme <[email protected]>:

Reopened #271 <#271>. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#271 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAeG3DmbIFTmwL8HaY-kDjkuenYcsnTDks5tksTWgaJpZM4SlT7C> .

[k-okada]

need to merge #273

[Affonso-Gui]

@inabajsk Please review

[Affonso-Gui]

To give a better explanation of the problem:

Symbols generated by (gensym) cannot be correctly readen from files, creating different objects for the same symbol representation.

(apply #'eq (read-from-string "(#:test #:test)"))
  ;; -> nil

This causes problems e.g. when trying to load hash tables from dumped files, as reported on #266.

In common lisp, this problem is solved by writing files using labeled notation, when *print-circle* is non-nil.

(let* ((g (gensym))
       (lst (list g g))
       (*print-circle* t))
  (format t "~s" lst))
;; -> (#1=#:G966 #1#)

(apply #'eq (read-from-string "(#1=#:G966 #1#)"))
  ;; -> t

This PR takes the same approach as common lisp implementation. It can be tested with the following:

(let ((lst (let ((g (gensym))) (list g g)))
      (*print-circle* t))
  (assert
   (apply #'eq (read-from-string (format nil "~S" lst)))
   "Unable to read uninterned symbol"))

[k-okada]

can you put test code into jskeus/irteus/test ?

[Affonso-Gui]

@k-okada added in euslisp/jskeus#501

[Affonso-Gui]

@k-okada ping