[Openmcl-devel] goblock

Taoufik Dachraoui dachraoui.taoufik at gmail.com
Sat Feb 23 10:12:01 UTC 2013


Hi

I needed to have a computed GO in one of my developments
I could not use tagbody so I developed a macro using
nfunctions and replace go by a funcall

in order to improve performance I use (return-from block (funcall f))

where all nfunctions have the form (lambda () (block name body))

I was hoping that the compiler will replace (return-from name (funcall f))
as a simple jump but this was not the case

Even though I found a simple implementation using tagbody
I would like to know why the compiler do not consider
  (return-from block (funcall f)) as a simple jump

With the simple implementation using tagbody, as fast as the tagbody,
 I can do the following:

(defun bar ()
  (let ((tags '(h e l l o end))
        (n 0))
    (tagblock nil
       start (incf n) (goto (pop tags))
       end (return-from nil n)
       h (princ 'h) (go start)
       e (princ 'e) (go start)
       l (princ 'l) (go start)
       o (princ 'o) (go start)
       )))

as you can see (goto expr) will compute expr and the (go <result of expr>)

Kind regards
Taoufik
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