October 2013 - cmucl-imp - mailman3.common-lisp.net

Re: [cmucl-imp] [Sbcl-devel] [Didier Verna] multiple string reads/writes of SB-IMPL::BAKQ-COMMA
by Didier Verna 14 Oct '13

14 Oct '13

Douglas Katzman <dougk(a)google.com> wrote: > You'll get correct results doing it this way - > > (s (write-to-string (read s) :pretty nil :readably t)) Yes. In fact, I was fooled by the fact that PRIN1 and friends are described to produce output suitable "for input to READ", but in fact don't bind *PRINT-READABLY* (this is even mentioned explicitly in the CLHS...). -- Resistance is futile. You will be jazzimilated. Lisp, Jazz, Aïkido: http://www.didierverna.info

1 0

Re: [cmucl-imp] [Sbcl-devel] [Didier Verna] multiple string reads/writes of SB-IMPL::BAKQ-COMMA
by Faré 11 Oct '13

11 Oct '13

The heart of the issue is that the pretty-printer for LET forms is confused by the comma. A workaround would be to use (let ((,obj nil)) ...) A fix would be to fix the pretty-printer of LET recognize SB-IMPL::BACKQ-COMMA (and while we're at it FARE-QUASIQUOTE::UNQUOTE, etc.?) or better, to be less clever with the printing of bindings, just setting the start column? —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org A successful [software] tool is one that was used to do something undreamed of by its author. — S. C. Johnson On Fri, Oct 11, 2013 at 9:09 AM, Douglas Katzman <dougk(a)google.com> wrote: > You'll get correct results doing it this way - > > (with-input-from-string (s "(defmacro test (&body body) > (let ((obj (gensym))) > `(let (,obj) > (setq ,obj (list ,@body)) > ,obj)))") > (eval (with-input-from-string > (s (write-to-string (read s) :pretty nil :readably t)) > (read s)))) > > > > > On Fri, Oct 11, 2013 at 4:27 AM, Didier Verna <didier(a)lrde.epita.fr> wrote: >> >> >> Hi, >> >> on second thought, I'm forwarding this to sbcl-devel because I think >> this might be a bug. The same scenario works fine with CCL. CMUCL gives >> a note and a warning but still works: >> >> CL-USER> (test 'a 'b) >> ; In: TEST 'A >> >> ; (TEST 'A 'B) >> ; ==> >> ; (LET (#) >> ; (SETQ #:G0 #) >> ; #:G0) >> ; Note: Variable LISP::BACKQ-COMMA defined but never used. >> ; ; >> >> ; Warning: These variables are undefined: >> ; #:G0 OBJ >> ; (A B) >> >> The macroepansion is however similar to that of SBCL: >> >> CL-USER> (macroexpand '(test 'a 'b)) >> (LET ((LISP::BACKQ-COMMA OBJ)) >> (SETQ #:G4368 (LIST 'A 'B)) >> #:G4368) >> T >> >> >> >> >> >> >> ---------- Forwarded message ---------- >> From: Didier Verna <didier(a)lrde.epita.fr> >> To: SBCL Help <sbcl-help(a)lists.sourceforge.net> >> Cc: >> Date: Fri, 11 Oct 2013 09:14:06 +0200 >> Subject: multiple string reads/writes of SB-IMPL::BAKQ-COMMA >> >> Hello, >> >> the backquote syntax gives me a problem when doing multiple (in fact 2) >> reads and writes of an expression. Consider this: >> >> CL-USER> (defmacro test (&body body) >> (let ((obj (gensym))) >> `(let (,obj) >> (setq ,obj (list ,@body)) >> ,obj))) >> TEST >> CL-USER> (test 'foo 'bar) >> (FOO BAR) >> >> >> CL-USER> (with-input-from-string (s "(defmacro test (&body body) >> (let ((obj (gensym))) >> `(let (,obj) >> (setq ,obj (list ,@body)) >> ,obj)))") >> (eval (read s))) >> STYLE-WARNING: redefining COMMON-LISP-USER::TEST in DEFMACRO >> TEST >> CL-USER> (test 'foo 'bar) >> (FOO BAR) >> >> ;; Okay, but then... >> >> >> CL-USER> (with-input-from-string (s "(defmacro test (&body body) >> (let ((obj (gensym))) >> `(let (,obj) >> (setq ,obj (list ,@body)) >> ,obj)))") >> (eval (with-input-from-string (s (prin1-to-string (read s))) >> (read s)))) >> STYLE-WARNING: redefining COMMON-LISP-USER::TEST in DEFMACRO >> TEST >> CL-USER> (test 'foo 'bar) >> ; in: TEST 'FOO >> ; (LET ((SB-IMPL::BACKQ-COMMA OBJ)) >> ; (SETQ #:G2191 (LIST 'FOO 'BAR)) >> ; #:G2191) >> ; >> ; caught STYLE-WARNING: >> ; The variable SB-IMPL::BACKQ-COMMA is defined but never used. >> >> ; (SETQ #:G2191 (LIST 'FOO 'BAR)) >> ; >> ; caught WARNING: >> ; undefined variable: #:G2191 >> >> >> and it breaks. What happens is that in the first case, SBCL understands >> that (SB-IMPL::BACKQ-COMMA OBJ) really means ,obj in the let form, but >> if I read this expression, write it to a string and read it again for >> evaluation, then it thinks that I'm trying to bind SB-IMPL::BACKQ-COMMA >> to OBJ... >> >> >> How can I avoid this behavior ? >> >> >> Thanks ! >> >> -- >> Resistance is futile. You will be jazzimilated. >> >> Lisp, Jazz, Aïkido: http://www.didierverna.info >> >> >> >> -- >> Resistance is futile. You will be jazzimilated. >> >> Lisp, Jazz, Aïkido: http://www.didierverna.info >> >> >> ------------------------------------------------------------------------------ >> October Webinars: Code for Performance >> Free Intel webinars can help you accelerate application performance. >> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most >> from >> the latest Intel processors and coprocessors. See abstracts and register > >> >> http://pubads.g.doubleclick.net/gampad/clk?id=60134071&iu=/4140/ostg.clktrk >> _______________________________________________ >> Sbcl-devel mailing list >> Sbcl-devel(a)lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/sbcl-devel >> > > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most > from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134071&iu=/4140/ostg.clktrk > _______________________________________________ > Sbcl-devel mailing list > Sbcl-devel(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/sbcl-devel >

1 0

[cmucl-imp] [Didier Verna] multiple string reads/writes of SB-IMPL::BAKQ-COMMA
by Didier Verna 11 Oct '13

11 Oct '13

Hi, on second thought, I'm forwarding this to sbcl-devel because I think this might be a bug. The same scenario works fine with CCL. CMUCL gives a note and a warning but still works: CL-USER> (test 'a 'b) ; In: TEST 'A ; (TEST 'A 'B) ; ==> ; (LET (#) ; (SETQ #:G0 #) ; #:G0) ; Note: Variable LISP::BACKQ-COMMA defined but never used. ; ; ; Warning: These variables are undefined: ; #:G0 OBJ ; (A B) The macroepansion is however similar to that of SBCL: CL-USER> (macroexpand '(test 'a 'b)) (LET ((LISP::BACKQ-COMMA OBJ)) (SETQ #:G4368 (LIST 'A 'B)) #:G4368) T -- Resistance is futile. You will be jazzimilated. Lisp, Jazz, Aïkido: http://www.didierverna.info

1 0