Version 0.8.8

Common Lisp threading library


Value type:

an alist mapping symbol names to forms to evaluate.

Initial value:



Variables named in this list are locally bound in the new thread, before it begins executing user code, by calling eval on its associated form.

This variable may be rebound around calls to make-thread to add/alter default bindings. The effect of mutating this list is undefined, but earlier forms take precedence over later forms for the same symbol, so defaults may be overridden by consing to the head of the list.

The bindings in *default-special-bindings* are used to determine the initial bindings of a new thread, and take precedence over a default list of I/O bindings. The list of initial I/O bindings is not modifiable by the user and it was chosen to avoid potential implementation-defined differences in with-standard-io-syntax.

*package*                   (find-package :common-lisp-user)
*print-array*               t
*print-base*                10
*print-case*                :upcase
*print-circle*              nil
*print-escape*              t
*print-gensym*              t
*print-length*              nil
*print-level*               nil
*print-lines*               nil
*print-miser-width*         nil
*print-pprint-dispatch*     (copy-pprint-dispatch nil)
*print-pretty*              nil
*print-radix*               nil
*print-readably*            t
*print-right-margin*        nil
*random-state*              (make-random-state t)
*read-base*                 10
*read-default-float-format* 'double-float
*read-eval*                 nil
*read-suppress*             nil
*readtable*                 (copy-readtable nil)


;;; Make a thread read integers in base 7.
(let* ((bt2:*default-special-bindings*
        (acons '*read-base* 7
       (thread (bt2:make-thread (lambda () (read-from-string "10")))))
  (bt2:join-thread thread))

=> 7, 2

See also:



The binding code does not check whether a symbol is indeed declared special or not.

Last updated on 2022-01-07
Published on 2022-01-07
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