[Openmcl-devel] process-run-function and "dynamic vs lexical"
greg at clozure.com
Thu Oct 22 16:08:09 UTC 2009
On 22 Oct 2009, at 11:42, Taoufik Dachraoui wrote:
> Just for completeness I include the example:
> ? (defvar y 1)
> ? (let ((x 2) (y 3))
> (labels ((f () (format t "~%x=~A y=~A~%" x y)))
> (ccl:process-run-function "test" #'f)))
> #<PROCESS test(3) [Reset] #x8D43546>
> x=2 y=1
> let creates new variable binding for the names x and y and these
> bindings are lexical unless they are declared special.
> Where is my mistake, please note here that I would like to reconcile
> my understanding with what I see while running ccl code.
If you check Ron's guide to specials (http://www.flownet.com/ron/specials.pdf
), the section "The pervasiveness of DEFVAR" explains what you're
"Because DEFVAR does more than just establish a dynamic binding for X.
It pervasively declares all references to X and all subsequent
bindings for X to be dynamic (or special -- same thing). In other
words, DEFVAR turns its argument (permanently and pervasively) into a
So the Y <= 3 binding is actually for the special variable, but the
binding of the 3 is thread-local, so your function run in its own
thread still sees the value 1.
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