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Showing posts from 2008

out-of-memory: a sad case

the problem..while Turing machine's tape is infinite, all real world programs are running within some resource constraints -- there is no such thing as infinite memory. for some programs that ain't a problem -- amount of memory needed by the algoritm can bee known beforehands, at programming time. but for most real world applications memory requirements are not known until run time, and sometimes it is very hard to predict how much does it need.obvious example is an application that allocates memory according to a user input -- for example, an image editor asks user for a dimension of an image he'd like to create. it needs to allocate an array in memory for the image (to have a fast access), so when dimensions exceed possible bounds, good-behaving application should notify user -- and user can either reduce image size or, perhaps, upgrade his machine, if he really wants to work with large images. while it is fairly easy to implement such functionality on a single-task OS, …

Lisp syntax is great!

lots of people complain about Lisp syntax -- they find it too weird and verbose, they call LISP "Lots of Irritating  Silly Parentheses"; and sometimes they even pop up with proposals to "fix Lisp" on comp.lang.lisp -- "Lisp is sort of cool, but this syntax... let me show you my great ideas."on the other hand, most lispers (and I among them) actually love s-expression syntax.who is right here? are syntax preferences a subjective thing, or one can decide which is better quite in an (more-or-less) objective way? or, perhaps, that's just a matter of taste and custom?i've got a good example today.. i'm using Parenscript -- cool Common Lisp library that automatically generates JavaScript from Lisp-like syntax -- and i've wrote a function that caches document.getElementById results (that makes sence for dumb browsers like IE):   (defun my-element-by-id (cache id) (return (or (slot-value cache id)     (setf (slot-value cache id)…

Lisp web tutorial?

"PHP vs. Lisp: Unfortunately, it's true..." article initiated quite active discussion on reddit, one fellow asking:Can someone post a tutorial for taking a clean install of Ubuntu (or windows or anything) to finish with serving a basic CRUD application using lisp? Maybe a TODO list with entires consisting of: incomplete/complete boolean, due date, subject, body?actually i had an impression that there are more than enough such tutorials, but as nobody replied i've tried finding one myself, starting with Hunchentoot tutorials. surprisingly, none of them covered a short path from clean OS install to working examples. neither i've found my ABCL-web  tutorial suitable for this, so i decided to try myself. my idea was that Linux distros like Debian and Ubuntu contain a lot of Lisp packages, and it should be fairly easy to install them, as it automatically manages dependencies etc. i've decided to try Hunchentoot -- i'm not using it myself, but it's known t…

Sorry, no manpages available for db_open.

today trying to find a manual page for db_open function of BerkeleyDB in Google gave me sort of surprise -- first 6 links were broken! that's a bit unusual -- often you get one or more broken page, but six in a row is some kind of anomaly. first working link was on Oracle site, so I wonder -- was it Oracle pulling BDB docs from other sites? so here's what Google returned to me:Berkeley DB: db_open The db_open function opens the database represented by file for both reading and writing. ... Also, calling db_open is a reasonably expensive operation. ... pegasus.cs.csubak.edu/docs/berkeley_debugger/api_c/Db/open.htmlsite fails to open Проект OpenNet: MAN db_open (3) Библиотечные вызовы (FreeBSD и Linux) db_open (3). Руководство не найдено. - 1. Команды и прикладные программы пользовательского уровня, русские | linux | freebsd | solaris | разные | posix ... www.opennet.ru/cgi-bin/opennet/man.cgi?topic=db_open&category=3text says manual not found -- but why is there a link on i…