August 2012 - alexandria-devel - mailman3.common-lisp.net

[alexandria-devel] latest alexandria doesn't build on ECL due to non-standard LOOP
by Anton Vodonosov 18 Jan '18

18 Jan '18

Hello. Alexandria in the latest quicklisp has a regression comparing to quicklisp 2012-02-08. It doesn't build on ECL because on non-standard LOOP construct (it is tolerated by most Lisps, but not by ECL; see here: http://comments.gmane.org/gmane.lisp.ecl.general/3344) The compiler complains about copy-stream method in io.lisp. Build logs: https://cl-test-grid.appspot.com/blob?key=AMIfv97xRRWJgLOa5TvS78VriRK9mQ82m… Best regards, - Anton

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[alexandria-devel] Adding a taste of Scheme to CL
by Pierre Thierry 27 Jan '13

27 Jan '13

Hi, after having followed SICP, I have been irremediably hooked on Scheme's let, so I added it to my macros. IIRC, I borrowed this implementation form SBCL's NAMED-LET (it's so short, it's hard to tell). I also heavily use a cataphoric IF, which I will now replace by the single-binding IF-LET, now that I know it exists. I thought it would be nice if LET@ was available in Alexandria with the other binding macros. Regards, Pierre

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[alexandria-devel] parse-ordinary-lambda-list
by Faré 26 Jan '13

26 Jan '13

An important missing information that parse-ordinary-lambda-list fails to return is whether there was a &key keyword. If I submit a patch to add that as an additional returned value, will it be integrated? —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org The American diplomat to the Russian: "My country too is free: in the USA too anyone may freely publish the dirty little secrets of president Medvedev!"

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[alexandria-devel] [Patch]: Fix an example in the docstring of iota.
by Stas Boukarev 26 Jan '13

26 Jan '13

An example in the docstring of iota was (iota 4) => (0 1 2 3 4) while it should've been (iota 4) => (0 1 2 3). -- With best regards, Stas.

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[alexandria-devel] Question about FORMAT-SYMBOL
by Luís Oliveira 26 Jan '13

26 Jan '13

Hello, I often try to support Allegro's modern mode by doing things like (format-symbol t "~A-~A" :foo :bar). We just came across an issue on #quicklisp where a user had set his *PRINT-CASE* to :DOWNCASE and that caused FORMAT-SYMBOL to intern lower-case symbols, thus breaking the idiom I described. Should fix my code to use SYMBOLICATE instead or should FORMAT-SYMBOL use WITH-STANDARD-IO-SYNTAX? Any opinions? -- Luís Oliveira http://r42.eu/~luis

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[alexandria-devel] Documentation fix and feature suggestion
by Jan Moringen 26 Jan '13

26 Jan '13

Dear alexandria developers, please the documentation fix and new functions in the two most recent commits in git://github.com/scymtym/alexandria.git for inclusion. Many thanks in advance. Kind regards, Jan

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[alexandria-devel] Regarding %MULTIPLY-RANGE, BINOMIAL-COEFFICIENT
by Robert Smith 26 Jan '13

26 Jan '13

Hello all. I've been trying to speed up BINOMIAL-COEFFICIENT for combinatorial calculations and ended up writing my own functions which were originally based off of Alexandria's design. For computing the binomial coefficient of (10^11, 10^5), Alexandria's takes about 9.990 seconds on my 64-bit Windows machine with a relatively recent SBCL with (optimize speed (safety 0) (debug 0)). I've ended up writing my own version of %MULTIPLY-RANGE, which I ended up calling RANGE-PRODUCT, and it's definition is: (declaim (ftype (function (integer integer) integer) range-product)) (defun range-product (lower upper) "Compute LOWER * (LOWER+1) * ... * (UPPER-1) * UPPER." (assert (<= lower upper)) (case (- upper lower) ((0) lower) ((1) (* lower upper)) (otherwise (let ((mid (floor (+ lower upper) 2))) (* (range-product lower mid) (range-product (1+ mid) upper)))))) [ from QTILITY: https://bitbucket.org/tarballs_are_good/qtility/src/65eff10fdece/arithmetic… ] >From that, the definition of FACTORIAL follows: (declaim (ftype (function ((integer 0)) (integer 1)) factorial)) (defun factorial (n) "Compute the factorial of N, N! = 1 * 2 * ... * N." (if (zerop n) 1 (range-product 1 n))) [ from QTILITY: https://bitbucket.org/tarballs_are_good/qtility/src/65eff10fdece/arithmetic… ] Then, I wrote BINOMIAL-COEFFICIENT that uses a closure to direct the swapping of the K and N-K, instead of mutating them. This seemed to at least help with SBCL's flow analysis. I also chose not to use CHECK-TYPE in favor of declarations (which I understand are not the same, but I think they should attempt to act the same given a sufficient compiler policy). (declaim (ftype (function ((integer 0) (integer 0)) (integer 0)) binomial-coefficient)) (defun binomial-coefficient (n k) "Binomial coefficient of N and K." (assert (>= n k)) (labels ((core (k n-k) (if (= 1 n-k) n (nth-value 0 (floor (range-product (+ k 1) n) (factorial n-k)))))) (declare (inline core) (ftype (function ((integer 0) (integer 0)) (integer 0)) core)) (if (or (zerop k) (= n k)) 1 (let ((n-k (- n k))) (declare (type (integer 0) n-k)) (if (< k n-k) (core n-k k) (core k n-k)))))) [ from QTILITY: https://bitbucket.org/tarballs_are_good/qtility/src/65eff10fdece/arithmetic… ] With the code above, I can compute the same binomial coefficient in about 7.503 seconds, so about a 2.5 second speed up. I'd like to submit a patch using the code above, but I could see how these speed ups are both implementation-dependent and platform-dependent. A particular unfortunate consequence is that we don't have those tweakable limits which (in theory; as the comments say) could be computed at compile time. Any thoughts? -Robert

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