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346 discussions

[pro] Reader macro definition in CLHS
by Kazimir Majorinc 02 Mar '11

02 Mar '11

------------------- reader macro n. 1. a textual notation introduced by dispatch on one or two characters that defines special-purpose syntax for use by the Lisp reader, and that is implemented by a reader macro function. See Section 2.2 (Reader Algorithm). 2. the character or characters that introduce a reader macro[1]; that is, a macro character or the conceptual pairing of a dispatching macro character and the character that follows it. (A reader macro is not a kind of macro.) ------------------- I do not understand item 1. In code ... (set-macro-character #\G (lambda(s c) 9.81)) (setf s (* (/ G 2) (* tt tt))) #\G is the reader-macro in a sense 2. What is the reader-macro in a sense 1.? Kazimir Majorinc

3 2

[pro] Common Lisp Library for MS Word files (.doc or .docx)?
by Mark H. David 01 Mar '11

01 Mar '11

Does anyone know of any CL libraries for dealing with Microsoft Word files? Tools for creating them, reading from them, parsing them, converting them to plain text or other formats, things like that? Thanks, -Mark

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[pro] Is cl-yacc going to cut it?
by Matthew D. Swank 15 Feb '11

15 Feb '11

I suppose this is only marginally related to common lisp, but everything I'm talking about is written in common lisp. I use cl-yacc for a lot of parsing, but one thing that has always seemed harder than it needs to be is writing lexers to feed it. One thing that I've found helpful is the creation of a custom lexer for each parser state by making the action table entry for that state available to the lexer. This provides the terminals the parser is looking for, and narrows the tokens the lexer has to look for at each step. However, this means I am also maintaining my own fork of cl-yacc. It seems (from my admittedly limited search) that this is not a common modification of yacc. Before I start bugging the maintainer about my changes, I want to know: am I abusing yacc? I do like the separation between low level tokenization the higher level symbol parse, but is there another general parsing technique, available as a lisp library of course, that either works at a lower level than yacc usually does or allows the lexer to access more context about the parse? Matt

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[pro] Final empty parameters to format directives
by Didier Verna 11 Feb '11

11 Feb '11

Hello, I just fell upon a case where implementations seem to differ on what to do. The question is how to interpret a format directive in which the last parameter is followed by a comma. Consider this test case: (defun fmt (stream argument colonp atsignp &rest params) (declare (ignore stream argument colonp atsignp)) (format t "~S~%" params)) (format t "~1,2/fmt/~%" t) (format t "~1,2,/fmt/~%" t) (format t "~1,2:/fmt/~%" t) (format t "~1,2,:/fmt/~%" t) Here's what you get from various implementations: SBCL / ECL / ABCL: (1 2) (1 2 NIL) (1 2) (1 2) CMU-CL / CCL / CLISP / Allegro / LispWorks: (1 2) (1 2) (1 2) (1 2) Funnily, my instinct tells me that nobody's right, as I would have expected to get this: (1 2) (1 2 NIL) (1 2) (1 2 NIL) Indeed, the parameters list is implicitely terminated by the directive character OR a colon / at-sign. So using a final comma seems to me like adding another, empty, parameter at the end. I'm willing to report those divergences to the respective implementations, but the problem is that I don't really know what to report :-) Who's right? No matter how I read the spec, I cannot make a decision and it seems to me that this is an unspecified corner case. I reckon it's probably not a big deal, but this could be a problem for user-defined functions relying on the actual number of parameters that they get. Comments? -- Resistance is futile. You will be jazzimilated. Scientific site: http://www.lrde.epita.fr/~didier Music (Jazz) site: http://www.didierverna.com

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[pro] Are you an Imager or a Filer?
by Ala'a Mohammad 10 Feb '11

10 Feb '11

Hi, I'm continually learning Common-lisp and trying to find the best style that suites me better. I've tried 'an imager' style (cooking a an image with all required libraries loaded when required), and 'a filer' style (loading files or systems each time I fire-up a CL implementation). I'm interested to hear what others use CL. How do they manage day to day work? how do their preferred style mesh into their production pipeline (coding, debugging, deployment and maintenance)? and what makes them prefer one way over another or the mix if applicable? Regards, Ala'a Mohammad.

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[pro] awk
by Daniel Weinreb 04 Feb '11

04 Feb '11

Has anybody written a domain-specific-language set of macros (or functions) to provide "awk" functionality from Common Lisp, with roughly the kind of brevity that awk users like? -- Dan

2 1

[pro] 404 animals
by Daniel Weinreb 03 Feb '11

03 Feb '11

There appears to be a new trend of putting cute animals on your HTTP 404 page. Twitter has a "Fail Whale", and now Tumblr has "TumblBeasts": http://www.observer.com/2011/tech/tumblr-adds-oatmeals-suggested-tumbeasts-… Perhaps we can have an easy way to make Lisp-based web sites use the "powered by alien technology" cute green creature? :) -- Dan

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Re: [pro] simple-style-warning
by Vladimir Sedach 27 Jan '11

27 Jan '11

So from what I understand now, the way to accomplish a "simple-style-warning" without having compile-file return failure-p is to define a subclass of style-warning with the format-control/arg slots and a :report function myself. Is this correct? Vladimir

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[pro] User defined format functions
by Didier Verna 26 Jan '11

26 Jan '11

Hello, there are situations in which I find myself frequently using the same format "pattern", which I'd like to abstract away. A concrete example is from my Declt package[1] which prints a lot in Texinfo format. Since Texinfo has a couple of special characters (e.g. @), I have an ESCAPE function which takes a string and returns another one with all special characters escaped. In the Declt code, I hence have very frequent calls which look like this: (format stream "... ~A ..." #|...|# (escape str) #|...|#) This is frustrating because I would like to abstract away the relation "~A <-> #'escape". Of course there are solutions (I could provide my own wrapper around FORMAT in some way) but none of them seem satisfactory. I'm aware of the ~// construct, which I find extremely cumbersome. Does anybody actually use it? It seems to me that the package handling part, specifically, makes it totally unusable. Just imagine that I would need to do something like that if I were to use it: (format stream "... ~/com.dvlsoft.declt:escape/ ..." #|...|# str #|...|#) and you get the idea! :-) No, in fact, the problem is that FORMAT control sequences are not extensible. This reminds me of something that we have in the Gnus mail/newsreader. It's called "user format functions". Gnus Group and Summary buffer lines, for example, are define by a format string with a set of predefined %<char> constructs. One of them, %u<char> lets you define and use your own function, called gnus-user-format-function-<char>. So what I would like to do is more or less define a function FORMAT-FUNCTION-E, just like a standard formatter, and then be able to write something like that: (format stream "... ~\e\ ..." #|...|# str #|...|#) Of course, there are package issues. Maybe we would need a centralized mapping between function names (what goes in ~\\) and actual symbols denoting the actual function? Possibly with the possibility to override the mapping by providing a package prefix in the ~\\ construct? In fact, the more I think about it, the more it sounds like having a format-table facility, much like what a readtable is, with a similar API. You could do (in-format-table :my-table-name) at the beginning of a file and have a totally customized set of format control sequences, possibly inheriting the standard ones. WDYT? Does something like that already exists[2]? Footnotes: [1] http://www.lrde.epita.fr/~didier/software/lisp/misc.php#declt [2] I've heard of something called fmt for scheme, but don't know much about it. -- Resistance is futile. You will be jazzimilated. Scientific site: http://www.lrde.epita.fr/~didier Music (Jazz) site: http://www.didierverna.com

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[pro] User defined format functions
by Didier Verna 25 Jan '11

25 Jan '11

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