December 2010 - alexandria-devel - mailman3.common-lisp.net

[alexandria-devel] [PATCH] add lastcons
by Mathieu Lemoine 30 Oct '11

30 Oct '11

Hi everyone. I made a little addition to the library. The lastcons function... It is very simple and I found myself thinking "that's something that ought to be in alexandria"... Not knowing the exact procedure to commit to the repo (and "git push" give me a "fatal: The remote end hung up unexpectedly" which is to be expected, I guess...), I send you the patch. Mathieu Lemoine.

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[alexandria-devel] patch to fix warning
by Antony 29 Oct '11

29 Oct '11

Hi I'd like to submit the following patch to get rid of the warning "In PROPER-LIST-LENGTH: Unused lexical variable LAST" I use Clozure Common Lisp Version 1.4-r13122 (WindowsX8664) Please check. Thanks, -Antony --- alexandria/lists.lisp 2010-12-10 09:05:44.649536400 -0800 +++ /home/antony/git/thirdparty/alexandria/lists.lisp 2010-12-10 09:25:01.388698100 -0800 @@ -196,7 +196,11 @@ (slow (cons (car list) (cdr list)) (cdr slow)) ,@(when step (list step))) (nil) - (declare (dynamic-extent slow) ,@(when declare (list declare))) + (declare (dynamic-extent slow) + ,@(when declare + (if (and (consp declare) (consp (car declare))) + declare + (list declare)))) (when (safe-endp fast) (return ,ret1)) (when (safe-endp (cdr fast)) @@ -209,7 +213,7 @@ ;; KLUDGE: Most implementations don't actually support lists with bignum ;; elements -- and this is WAY faster on most implementations then declaring ;; N to be an UNSIGNED-BYTE. - (fixnum n) + ((ignorable last) (fixnum n)) (1- n) n)

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[alexandria-devel] reductions
by Cyrus Harmon 29 Oct '11

29 Oct '11

Hi Alexandrians, Clojure has a function that I occasionally find useful, reductions. It's like reduce, only it returns not the last value of calling the two-arg function, but a list consisting of the first element of the input sequence, followed by the result of calling the two-arg with the first and second elements of the input sequence, then the result of calling the two-arg function with the previous result and the third element, and so on... e.g.: CL-USER> (reductions #'+ '(1 2 3 4)) (1 3 6 10) Here's the code. There are probably better ways to do this, but this is at least portable and simple. I think this would be a useful addition to alexandria. (defun reductions (function sequence &rest args) (let ((l (list (first sequence)))) (apply #'reduce (lambda (a b) (let ((val (funcall function a b))) (push val l) val)) sequence args) (nreverse l))) thanks, Cyrus

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[alexandria-devel] [RFC] collect-duplicates
by Andreas Fuchs 07 Dec '10

07 Dec '10

Hi there, Prompted by a discussion on #lisp, I've made the following collect-duplicates function: Takes a sequence and a test, and returns as two values a sequence of duplicates and a sequence of the duplicate count (matching their sequence type to the input sequence's). (defun collect-duplicates (sequence &key (test #'eql)) ;; This will work only for TESTs that are valid hash tests: (let ((dupes (make-hash-table :test test)) (known (make-hash-table :test test))) (map nil (lambda (elt) (if (gethash elt known) (incf (gethash elt dupes 1)) (setf (gethash elt known) t))) sequence) (let ((duplicates (make-sequence (class-of sequence) (hash-table-count dupes))) (counts (make-sequence (class-of sequence) (hash-table-count dupes))) (i 0)) (maphash (lambda (k v) (setf (elt duplicates i) k (elt counts i) v) (incf i)) dupes) (values duplicates counts)))) Issues that I see with it: * Needs a :key argument. * :test should allow for non-hash-table tests, as well. * (class-of ...) is not really a good idea, as it doesn't preserve the element type for arrays. If I fixed these issues, would there be interest in having this function in alexandria? Cheers, -- Andreas Fuchs, (http://|im:asf@|mailto:asf@)boinkor.net, antifuchs

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