pro November 2017

pro@common-lisp.net

18 participants
7 discussions

ASDF debugging on Hangouts?
by Faré 27 Dec '17

27 Dec '17

Dear CLers, with ASDF 3.3.1 released and the syntax-control branch pending review, there's not much left for me to do with ASDF before I actually retire. Now I'm looking for hackers to whom to pass the torch of ASDF hacking. It so happens that I seem to have introduced (probably with 3.3.0) a regression that breaks static image dumping of workout-timer with cffi-toolchain. If people are interested, I could do the entire debugging session over Google Hangouts, from isolating the bug and filing a bug report to writing regression test and submitting a merge request. That would be a good way to introduce newcomers to ASDF hacking. Having a public ask questions as I make progress would be a good way to keep the video relevant. Is anyone interested? —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org If there's a book you really want to read but it hasn't been written yet, then you must write it. — Toni Morrison [same with software, —♯f]

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Re: ML Maintainer wanted
by Sky Hester 02 Dec '17

02 Dec '17

Seems like it would be a good service to keep up. I volunteer, if no one else has already spoken up. -Sky On Nov 30, 2017 5:53 AM, "Hans Hübner" <hans.huebner(a)gmail.com> wrote: Hi, I would like to step down from being the pro@ mailing list maintainer. It is not a lot of regular work (maybe one or two visits to the Mailman page per month to forward or reject a message from a non-subscriber), but it might be that the list needs to be moved or something and I would like to avoid getting into a situation where maintenance is required and I don't have time to do it. Also, I'm not a professional Common Lisp user anymore, so I don't qualify for the list at this point anyway :D Any takers? Thanks, Hans

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Re: ML Maintainer wanted
by Hans Hübner 30 Nov '17

30 Nov '17

2017-11-30 17:13 GMT+01:00 R. Matthew Emerson <rme(a)acm.org>: > Well, I assume the password isn't going to be that for much longer, since > it was accidentally sent out to the mailing list... :-O > Nice one! 30 years of email and I still can't work it out! Sky is nominated to be the keeper of the new password. :) Cheers, Hans

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ML Maintainer wanted
by Hans Hübner 30 Nov '17

30 Nov '17

Hi, I would like to step down from being the pro@ mailing list maintainer. It is not a lot of regular work (maybe one or two visits to the Mailman page per month to forward or reject a message from a non-subscriber), but it might be that the list needs to be moved or something and I would like to avoid getting into a situation where maintenance is required and I don't have time to do it. Also, I'm not a professional Common Lisp user anymore, so I don't qualify for the list at this point anyway :D Any takers? Thanks, Hans

1 0

Optimizing a function over multiple types for its arguments
by Chaitanya Gupta 28 Nov '17

28 Nov '17

While I was working on qbase64[1], I stumbled over a peculiar problem: I wanted it to work as fast as possible when optimized array types (SIMPLE-ARRAY, SIMLPE-BASE-STRING, etc.) were passed to the encoding/decoding routines, but I also wanted to support the more general types. If I defined my core encoding routine like this: (defun %encode (bytes string) (declare (type (simple-array (unsigned-byte 8)) bytes)) (declare (type simple-base-string string)) (declare (optimize speed)) ...) SBCL would produce very fast code, but the function would no longer work for other ARRAY or STRING types: And if I was to redefine the routine with more general types: (defun %encode (bytes string) (declare (type array bytes)) (declare (type string string)) (declare (optimize speed)) ...) The code produced would be significantly slower. My solution to this conundrum was to create a macro that would take all the different type combinations I wanted to optimize and support upfront: (defun/td %encode (bytes string) (((bytes (simple-array (unsigned-byte 8))) (string simple-base-string)) ((bytes (simple-array (unsigned-byte 8))) (string simple-string)) ((bytes array) (string string))) (declare (optimize speed)) ...) and generate code which would dispatch over the type combinations, then use LOCALLY to actually declare the types and splice the body in: (defun %encode (bytes string) (cond ((and (typep bytes '(simple-array (unsigned-byte 8))) (typep string 'simple-base-string)) (locally (declare (type bytes (simple-array (unsigned-byte 8)))) (declare (type string simple-base-string)) (declare (optimize speed)) ...)) ((and (typep bytes '(simple-array (unsigned-byte 8))) (typep string 'simple-string)) (locally (declare (type bytes (simple-array (unsigned-byte 8)))) (declare (type string simple-string)) (declare (optimize speed)) ...)) ((and (typep bytes 'array) (typep string 'string)) (locally (declare (type bytes array)) (declare (type string string)) (declare (optimize speed)) ...)) (t (error "Unsupported type combination")))) If the run-time dispatch incurs a slight penalty, it is more than offset by gains made by using optimized array types, esp. since these routines have to typically visit every element of the given arrays. I was wondering if there was a better way to do this. Have I missed a trick or two? I was reading about the Lisp Interface Library[2] which supports parametric polymorphism, but not sure if it would result in optimized code like the one my macro generates. Chaitanya 1. https://github.com/chaitanyagupta/qbase64 2. https://common-lisp.net/%7Efrideau/lil-ilc2012/lil-ilc2012.html

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lisp.org
by Nick Levine 20 Nov '17

20 Nov '17

Now that we've established why lisp.org and its friends are long-term off air... The website at lisp.org contained a photo of John McCarthy (and nothing else) since the week he died six years ago. What's the message? In contrast take a quick look at (say) python.org, a site devoted to really assisting people to use that language. Do we care, and if we do how do we go about effecting change? - nick

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Can compiler macros make use of type declarations?
by Chaitanya Gupta 09 Nov '17

09 Nov '17

Let's say I have created a function called `FOO`: (defun foo (x) ...) To optimize this function, I write a compiler macro. Can I make use of type declarations that users of `FOO` might have made for the argument `X` that is passed in to it? That is, let's say `FOO` is used like this: (let ((a (something-that-returns-an-integer))) (declare (integer a)) (foo a)) The compiler macro for `FOO` cannot make any optimizations on the value of `A`, but can it take advantage of the fact that `A` is declared as in `INTEGER` here? Chaitanya

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