[comp.lang.lisp] [ANN] Sacla loop: a new loop implementation

[Sam S. <sd...@gn...>]

* destructuring on the result of multiple-value-list form is transformed
  to a multiple-value-setq form, reducing the amout of consing.
  e.g. (macroexpand '(loop for (a b c) = (multiple-value-list (foo))))
       => (BLOCK NIL
            (LET ((A NIL) (B NIL) (C NIL))
              (MACROLET ((LOOP-FINISH NIL '(GO #:LOOP-EPILOGUE-7002)))
                (TAGBODY
                   #:LOOP-BODY-7001
                   (MULTIPLE-VALUE-SETQ (A B C) (FOO))
                   (GO #:LOOP-BODY-7001)
                   #:LOOP-EPILOGUE-7002))))

CLISP is _much_ worse:

(MACROLET ((LOOP-FINISH NIL (SYSTEM::LOOP-FINISH-ERROR)))
 (BLOCK NIL
  (LET ((#:G415 NIL))
   (LET ((A NIL) (B NIL) (C NIL))
    (LET NIL
     (MACROLET ((LOOP-FINISH NIL '(GO SYSTEM::END-LOOP)))
      (TAGBODY
       (SETQ A (CAR (SETQ #:G415 (MULTIPLE-VALUE-LIST (FOO)))) B
        (CAR (SETQ #:G415 (CDR #:G415))) C (CAR (CDR #:G415)))
       SYSTEM::BEGIN-LOOP (PROGN)
       (PSETQ A (CAR (SETQ #:G415 (MULTIPLE-VALUE-LIST (FOO)))) B
        (CAR (SETQ #:G415 (CDR #:G415))) C (CAR (CDR #:G415)))
       (GO SYSTEM::BEGIN-LOOP) SYSTEM::END-LOOP
       (MACROLET
        ((LOOP-FINISH NIL (SYSTEM::LOOP-FINISH-WARN)
          '(GO SYSTEM::END-LOOP)))))))))))

1. conses in MULTIPLE-VALUE-LIST

2. has the MULTIPLE-VALUE-LIST code in 2 places

-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
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