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  • accessing a value of a nested hash

    - by st
    Hello! I am new to perl and I have a problem that's very simple but I cannot find the answer when consulting my perl book. When printing the result of Dumper($request); I get the following result: $VAR1 = bless( { '_protocol' => 'HTTP/1.1', '_content' => '', '_uri' => bless( do{\(my $o = 'http://myawesomeserver.org:8081/counter/')}, 'URI::http' ), '_headers' => bless( { 'user-agent' => 'Mozilla/5.0 (X11; U; Linux i686; en; rv:1.9.0.4) Gecko/20080528 Epiphany/2.22 Firefox/3.0', 'connection' => 'keep-alive', 'cache-control' => 'max-age=0', 'keep-alive' => '300', 'accept' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'accept-language' => 'en-us,en;q=0.5', 'accept-encoding' => 'gzip,deflate', 'host' => 'localhost:8081', 'accept-charset' => 'ISO-8859-1,utf-8;q=0.7,*;q=0.7' }, 'HTTP::Headers' ), '_method' => 'GET', '_handle' => bless( \*Symbol::GEN0, 'FileHandle' ) }, 'HTTP::Server::Simple::Dispatched::Request' ); How can I access the values of '_method' ('GET') or of 'host' ('localhost:8081'). I know that's an easy question, but perl is somewhat cryptic at the beginning. Thank you, St.

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  • Getting jQuery datepicker to attach to a TextBox within a ListView

    - by Clay
    I am using the jQuery Datepicker without any problem for TextBox controls that are non-templated. However, I am unable to get the datepicker to work with a TextBox that is in an EditItemTemplate of a ListView control. My latest attempt is to get a handle on this textbox by CSS class name "DateControl", any ideas? <asp:ListVIew id="lvTest" runat="server"> <LayoutTemplate>...</LayoutTemplate> <ItemTemplate>...</ItemTemplate> <EditItemTemplate> <tr> <td> <asp:TextBox ID="txtExpReceiveDate" runat="server" Text='<%#Eval("exp_receive_date","{0:dd-MMM-yy}") %>' CssClass="DateControl" /> </td> </tr> </EditTemplate> </asp:ListView> <script type="text/javascript" language="javascript"> $(document).ready(function () { $('DateControl').datepick({ dateFormat: 'M-dd-yyyy' }); }); </script>

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  • MySQL FULLTEXT aggravation

    - by southof40
    Hi - I'm having problems with case-sensitivity in MySQL FULLTEXT searches. I've just followed the FULLTEXT example in the MySQL doco at http://dev.mysql.com/doc/refman/5.1/en/fulltext-boolean.html . I'll post it here for ease of reference ... CREATE TABLE articles ( id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY, title VARCHAR(200), body TEXT, FULLTEXT (title,body) ); INSERT INTO articles (title,body) VALUES ('MySQL Tutorial','DBMS stands for DataBase ...'), ('How To Use MySQL Well','After you went through a ...'), ('Optimizing MySQL','In this tutorial we will show ...'), ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'), ('MySQL vs. YourSQL','In the following database comparison ...'), ('MySQL Security','When configured properly, MySQL ...'); SELECT * FROM articles WHERE MATCH (title,body) AGAINST ('database' IN NATURAL LANGUAGE MODE); ... my problem is that the example shows that SELECT returning the first and fifth rows ('..DataBase..' and '..database..') but I only get one row ('database') ! The example doesn't demonstrate what collation the table in the example had but I have ended up with latin1_general_cs on the title and body columns of my example table. My version of MySQL is 5.1.39-log and the connection collation is utf8_unicode_ci . I'd be really grateful is someone could suggest why my experience differs from the example in the manual ! Be grateful for any advice.

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  • Which to use, XMP or RDF?

    - by zotty
    What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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  • Objective C loop logic

    - by Graham
    Hi guys, I'm really new to programming in Obj-C, my background is in labview which is a graphical programming language, I've worked with Visual Basic some and HTML/CSS a fair amount as well. I'm trying to figure out the logic to create an array of data for the pattern below. I need the pattern later to extract data from another 2 arrays in a specific order. I can do it by referencing a = 1, b = 2, c = 3 etc and then creating the array with a, b, c but I want to use a loop so that I don't have 8 references above the array. These references will be used to generate another generation of data so unless I can get help figuring out the logic I'll actually end up with 72 references above the array. // This is the first one which gives the pattern 0 0 0 0 (etc) // 1 1 1 1 // 2 2 2 2 NSMutableArray * expSecondRef_one = [NSMutableArray array]; int a1 = 0; while (a1 < 9) { int a2 = 0; while (a2 < 8) { NSNumber * a3 = [NSNumber numberWithInt:a1]; [expSecondRef_one addObject:a3]; a2++; } a1++; } // This is the second one which I'm stumbling over, I am looking for the pattern 1 2 3 4 5 6 7 8 // 0 2 3 4 5 6 7 8 // 0 1 3 4 5 6 7 8 // 0 1 2 4 5 6 7 8 // etc to -> // 0 1 2 3 4 5 6 7 If you run it in a line every 9th number is -1 but I don't know how to do that over a pattern of 8. Thanks in advance! Graham

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  • Groovy / Scala / Java under the hood

    - by Jack
    I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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  • How to embed XBase expressions in an Xtext DSL

    - by Marcus Mathioudakis
    I am writing a simple little DSL for specifying constraints on messages, and Have been trying without success for a while to embed XBase expressions into the language. The Grammar looks like this: grammar org.xtext.businessrules.BusinessRules with org.eclipse.xtext.xbase.Xbase //import "http://www.eclipse.org/xtext/xbase/Xbase" as xbase import "http://www.eclipse.org/xtext/common/JavaVMTypes" as jvmTypes generate businessRules "http://www.xtext.org/businessrules/BusinessRules" Start: rules+=Constraint*; Constraint: {Constraint} 'FOR' 'PAYLOAD' payload=PAYLOAD 'ELEMENT' element=ID 'CONSTRAINED BY' constraint=XExpression; PAYLOAD: "SimulationSessionEvents" |"stacons" |"any" ; Range: 'above' min=INT ('below' max=INT)? |'below' max=INT ('above' min=INT)? ; When trying to parse a file such as: FOR PAYLOAD SimulationSessionEvents ELEMENT matrix CONSTRAINED BY ... I can't get it to work for ... = any kind of Arithmetic expression, although it works for ...= loop or if expression, or even just a number. As soon as I do something like '-5' or '4-5' it says Couldn't resolve reference to JvmIdentifiableElement '-', even though the Xbase.xtext Grammar looks like it allows these expressions. I don't think I'm missing any Jars, as it doesn't complain when I run the mwe workflow, but only when trying to parse the input file. Any help would be much appreciated.

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  • User Control not loading based on location

    - by mwright
    I have an ASP.net MVC solution that uses nested master pages to load content. On the first Master page I load a header, then have the Content Placeholder, and then load a footer. This master page is referenced by another master page which adds some additional information based on the user being logged in or not. When I load a page that references these master pages, the header loads, but the footer does not. If I move the footer up above the Content Place Holder it loads into the page. Any ideas why this might be the case? The code for the master page that contains the footer is as follows: <%@ Master Language="C#" Inherits="System.Web.Mvc.ViewMasterPage" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title> <asp:ContentPlaceHolder ID="TitleContent" runat="server" /> </title> </head> <body> <div class="header"> <% Html.RenderPartial("Header"); %> </div> <div> <asp:ContentPlaceHolder ID="MainContent" runat="server"> </asp:ContentPlaceHolder> </div> <div class="footer"> <% Html.RenderPartial("Footer"); %> </div> </body> </html>

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  • Yet another Haskell vs. Scala question

    - by Travis Brown
    I've been using Haskell for several months, and I love it—it's gradually become my tool of choice for everything from one-off file renaming scripts to larger XML processing programs. I'm definitely still a beginner, but I'm starting to feel comfortable with the language and the basics of the theory behind it. I'm a lowly graduate student in the humanities, so I'm not under a lot of institutional or administrative pressure to use specific tools for my work. It would be convenient for me in many ways, however, to switch to Scala (or Clojure). Most of the NLP and machine learning libraries that I work with on a daily basis (and that I've written in the past) are Java-based, and the primary project I'm working for uses a Java application server. I've been mostly disappointed by my initial interactions with Scala. Many aspects of the syntax (partial application, for example) still feel clunky to me compared to Haskell, and I miss libraries like Parsec and HXT and QuickCheck. I'm familiar with the advantages of the JVM platform, so practical questions like this one don't really help me. What I'm looking for is a motivational argument for moving to Scala. What does it do (that Haskell doesn't) that's really cool? What makes it fun or challenging or life-changing? Why should I get excited about writing it?

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  • Elegant way of parsing Data files for Simulation

    - by sc_ray
    I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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  • How to create an AST with ANTLR from a hierarchical key-value syntax

    - by Brabster
    I've been looking at parsing a key-value data format with ANTLR. Pretty straightforward, but the keys represent a hierarchy. A simplified example of my input syntax: /a/b/c=2 /a/b/d/e=3 /a/b/d/f=4 In my mind, this represents a tree structured as follows: (a (b (= c 2) (d (= e 3) (= f 4)))) The nearest I can get is to use the following grammar: /* Parser Rules */ start: (component NEWLINE?)* EOF -> (component)*; component: FORWARD_SLASH ALPHA_STRING component -> ^(ALPHA_STRING component) | FORWARD_SLASH ALPHA_STRING EQUALS value -> ^(EQUALS ALPHA_STRING value); value: ALPHA_STRING; /* Lexer Rules */ NEWLINE : '\r'? '\n'; ALPHA_STRING : ('a'..'z'|'A'..'Z'|'0'..'9')+; EQUALS : '='; FORWARD_SLASH : '/'; Which produces: (a (b (= c 2))) (a (b (d (= e 3)))) (a (b (d (= f 4)))) I'm not sure whether I'm asking too much from a generic tool such as ANTLR here, and this is as close I can get with this approach. That is, from here I consume the parts of the tree and create the data structure I want by hand. So - can I produce the tree structure I want directly from a grammar? If so, how? If not, why not - is it a technical limitation in ANTLR or is it something more CS-y to do with the type of language involved?

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  • Web development: Haskell or Scheme

    - by Robert E. Lester
    I would like to to choose one of these languages for building web applications. I'm not interested in framework per say, but have the following needs: Rapid development. Easy to scale. Strong community for the web. Quick and easy to deploy. I'm very familiar with Haskell, and have some familiarity with scheme (in particular PLT). Scheme appeals to me as good candidate for web development due to it's simple syntax which is homogenous across libraries. I state this despite my subjective opinion that Haskell is a 'cleaner' language. Haskell web apps seem to require learning and building a patchwork of different combinator libraries. On the plus side, I realise this can be quite expressive, although I'd prefer to eliminate impedance mismatches where possible. While scheme-plt looks to be a good fit, I can find but one example of it being used in the "real world". Haskell doesn't seem to fair too much better here, but there seems to be a bigger community behind the web side. Please help me make up my mind. For the most part I'm interested in real-world use cases.

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  • php (rar) i want to rar a folder using rar on Ubuntu (linux) by php (on dedi server) noob

    - by Steve
    hey guyz i want rar (not tar) my folder on my server by using php RAR RAR 3.93 Copyright (c) 1993-2010 Alexander Roshal 15 Mar 2010 Registered to my real name OS Ubuntu Release (Karmic) kernel linux 2.6.32.2-xxxx-grs-ipv4-32 Gnome 2.28.1 latest php an lighthttpd i have tried these things http://php.net/manual/en/function.escapeshellarg.php // may be wrong code http://php.net/manual/en/function.exec.php http://php.net/manual/en/function.shell-exec.php my command (working in ssh and nautilus script) rar a -m0 /where/file/will/saved/file_name.rar /location/ti/data/dir/datafolder php code $log=Shell_exec("rar a -m0 /where/file/will/saved/file_name.rar /location/ti/data/dir/datafolder"); echo $log; one method is left which i don't know how to use and its working on server that is by somefile_to_execute_command.sh i have to execute .sh file from php need to send some variables (command) and i tried this method can rar file with a script named RapidLeech but its rar from only its own files dir only :( but i want to do in different directories. Rapid Leech rar class http://paste2.org/p/791668 i m able run shell command with php (cp(copy),mv(move),ls(directory list),rm(remove aka delete)) but got failed to run rar i gives no output i also tried to given path rar and i used alot commands with php Shell_exec function and working like they work with ssh and i have tried almost 80 % method given on net and failed from last 3days i m over now plz help me i need php script file working plz reply if u have any info n code and experience about rar and this kinda :( problem i m 99% noob just used code mean search Google collect script make my own working thing (for personal use only) n now i m failed to rar folder and file :(( now plz provide me code plz don't talk in technical language because i m just reading my first php book (for dummies :D) mean noob and 0.1 plz help me as much u can thankx

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  • Ajax Javascript method cannot be called

    - by blackmage
    I made this method to load javascript functions dynamically. It does include the .js file but when I call a method, the method says that it is undefinited. The following to .js files are ajax_object.js and user_manager.js . The alert outside the function is read and works but the alert inside does not. enter code here //ajax_object.js //Load a javascript library function loadJavascript( src, url ){ XMLHttpRequestObject=getXmlHttpRequestObject(); if( XMLHttpRequestObject){ XMLHttpRequestObject.onreadystatechange = function() { if (XMLHttpRequestObject.readyState == 4 ){ if (XMLHttpRequestObject.status == 200 || XMLHttpRequestObject.status == 304) { includeJavaScript( src, url, XMLHttpRequestObject.responseText ); } } } } XMLHttpRequestObject.open('GET', url, true); XMLHttpRequestObject.send(null); }//end LoadJavaScript //Add Library to header function includeJavaScript(src, fileUrl, xmlObject) { if ( ( xmlObject != null ) && ( !document.getElementById( src ) ) ){ var documentHead = document.getElementsByTagName('HEAD').item(0); var includeScript = document.createElement( "script" ); includeScript.language = "javascript"; includeScript.type = "text/javascript"; //includeScript.id = src; includeScript.src=fileUrl.concat(src); includeScript.defer = true; includeScript.text = xmlObject; documentHead.appendChild( includeScript ); } } //user_manager.js //First alert is read alert("Outside User Manager"); function selectUserManagerModuleType(){ XMLHttpRequestObject=getXmlHttpRequestObject(); //This doesn't work //throws selectUserManagerModuleType undefined alert("Inside The User Manager"); }

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  • questions about name mangling in C++

    - by Tim
    I am trying to learn and understand name mangling in C++. Here are some questions: (1) From devx When a global function is overloaded, the generated mangled name for each overloaded version is unique. Name mangling is also applied to variables. Thus, a local variable and a global variable with the same user-given name still get distinct mangled names. Are there other examples that are using name mangling, besides overloading functions and same-name global and local variables ? (2) From Wiki The need arises where the language allows different entities to be named with the same identifier as long as they occupy a different namespace (where a namespace is typically defined by a module, class, or explicit namespace directive). I don't quite understand why name mangling is only applied to the cases when the identifiers belong to different namespaces, since overloading functions can be in the same namespace and same-name global and local variables can also be in the same space. How to understand this? Do variables with same name but in different scopes also use name mangling? (3) Does C have name mangling? If it does not, how can it deal with the case when some global and local variables have the same name? C does not have overloading functions, right? Thanks and regards!

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  • Python to C# with openSSL requirement

    - by fonix232
    Hey there again! Today I ran into a problem when I was making a new theme creator for chrome. As you may know, Chrome uses a "new" file format, called CRX, to manage it's plugins and themes. It is a basic zip file, but a bit modified: "Cr24" + derkey + signature + zipFile And here comes the problem. There are only two CRX creators, written in Ruby or Python. I don't know neither language too much (had some basic experience in Python though, but mostly with PyS60), so I would like to ask you to help me convert this python app to a C# class. Also, here is the source of crxmake.py: #!/usr/bin/python # Cribbed from http://github.com/Constellation/crxmake/blob/master/lib/crxmake.rb # and http://src.chromium.org/viewvc/chrome/trunk/src/chrome/tools/extensions/chromium_extension.py?revision=14872&content-type=text/plain&pathrev=14872 # from: http://grack.com/blog/2009/11/09/packing-chrome-extensions-in-python/ import sys from array import * from subprocess import * import os import tempfile def main(argv): arg0,dir,key,output = argv # zip up the directory input = dir + ".zip" if not os.path.exists(input): os.system("cd %(dir)s; zip -r ../%(input)s . -x '.svn/*'" % locals()) else: print "'%s' already exists using it" % input # Sign the zip file with the private key in PEM format signature = Popen(["openssl", "sha1", "-sign", key, input], stdout=PIPE).stdout.read(); # Convert the PEM key to DER (and extract the public form) for inclusion in the CRX header derkey = Popen(["openssl", "rsa", "-pubout", "-inform", "PEM", "-outform", "DER", "-in", key], stdout=PIPE).stdout.read(); out=open(output, "wb"); out.write("Cr24") # Extension file magic number header = array("l"); header.append(2); # Version 2 header.append(len(derkey)); header.append(len(signature)); header.tofile(out); out.write(derkey) out.write(signature) out.write(open(input).read()) os.unlink(input) print "Done." if __name__ == '__main__': main(sys.argv) Please could you help me?

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  • How spoof referrer using curl

    - by golu molu
    I am using curl code below to spoof referrer , it works fine but there is error on every page - Curl error: $url = somesite.com function doMagic($url) { $curl = curl_init(); $header[0] = "Accept: text/xml,application/xml,application/xhtml+xml,"; $header[0] .= "text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"; $header[] = "Cache-Control: max-age=0"; $header[] = "Connection: keep-alive"; $header[] = "Keep-Alive: 300"; $header[] = "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7"; $header[] = "Accept-Language: en-us,en;q=0.5"; $header[] = "Pragma: "; curl_setopt($curl, CURLOPT_URL, $url); curl_setopt($curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0.1) Gecko/20100101 Firefox/7.0.12011-10-16 20:23:00"); curl_setopt($curl, CURLOPT_HTTPHEADER, $header); curl_setopt($curl, CURLOPT_REFERER, "http://www.facebook.com"); curl_setopt($curl, CURLOPT_ENCODING, "gzip,deflate"); curl_setopt($curl, CURLOPT_AUTOREFERER, true); curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); curl_setopt($curl, CURLOPT_TIMEOUT, 30); curl_setopt($curl, CURLOPT_FOLLOWLOCATION,true); $html = curl_exec($curl); echo 'Curl error: '. curl_error($curl); curl_close($curl); return $html; } $text = doMagic($url); print("$text"); what i'm doing wrong?

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  • how would you like computer science classes to be taught?

    - by aaa
    hello I am a graduate student now, and hopefully someday I will teach. my interests are C++, Python, embedded languages, and scientific computing. Meanwhile I daydream about how I would teach. I was not quite happy with my undergraduate university as I found many computer science classes lacking. so I would like to ask you, if you were a student, how would you like your computer science classes to be taught? I understand it is a very subjective question, but nevertheless I think it's important to know what people want. Some specific points I am interested in: should computer languages be taught explicitly, or should students be required to pick up language on their own? what is better for learning, tests, projects, some sort of take-home exam? how do you think classtime should be used? theory, introduction, explanations, etc.? do you think the group projects are important? how much about computer architecture do you want to learn in computer science class, not necessarily assembler class. should particular operating system/editor be mandated or encouraged? Thanks thank you for your comments. Question has been closed because it is a discussion question rather than Q&A. If you know appropriate website for discussions of such sort with low noise ratio, please let me know.

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  • copy rows before updating them to preserve archive in Postgres

    - by punkish
    I am experimenting with creating a table that keeps a version of every row. The idea is to be able to query for how the rows were at any point in time even if the query has JOINs. Consider a system where the primary resource is books, that is, books are queried for, and author info comes along for the ride CREATE TABLE authors ( author_id INTEGER NOT NULL, version INTEGER NOT NULL CHECK (version > 0), author_name TEXT, is_active BOOLEAN DEFAULT '1', modified_on TIMESTAMP DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (author_id, version) ) INSERT INTO authors (author_id, version, author_name) VALUES (1, 1, 'John'), (2, 1, 'Jack'), (3, 1, 'Ernest'); I would like to be able to update the above like so UPDATE authors SET author_name = 'Jack K' WHERE author_id = 1; and end up with 2, 1, Jack, t, 2012-03-29 21:35:00 2, 2, Jack K, t, 2012-03-29 21:37:40 which I can then query with SELECT author_name, modified_on FROM authors WHERE author_id = 2 AND modified_on < '2012-03-29 21:37:00' ORDER BY version DESC LIMIT 1; to get 2, 1, Jack, t, 2012-03-29 21:35:00 Something like the following doesn't really work CREATE OR REPLACE FUNCTION archive_authors() RETURNS TRIGGER AS $archive_author$ BEGIN IF (TG_OP = 'UPDATE') THEN -- The following fails because author_id,version PK already exists INSERT INTO authors (author_id, version, author_name) VALUES (OLD.author_id, OLD.version, OLD.author_name); UPDATE authors SET version = OLD.version + 1 WHERE author_id = OLD.author_id AND version = OLD.version; RETURN NEW; END IF; RETURN NULL; -- result is ignored since this is an AFTER trigger END; $archive_author$ LANGUAGE plpgsql; CREATE TRIGGER archive_author AFTER UPDATE OR DELETE ON authors FOR EACH ROW EXECUTE PROCEDURE archive_authors(); How can I achieve the above? Or, is there a better way to accomplish this? Ideally, I would prefer to not create a shadow table to store the archived rows.

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  • How to manipulate *huge* amounts of data

    - by Alejandro
    Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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  • How to transform a production to LL(1) for a list separated by a semicolon?

    - by Subb
    Hi, I'm reading this introductory book on parsing (which is pretty good btw) and one of the exercice is to "build a parser for your favorite language." Since I don't want to die today, I thought I could do a parser for something relatively simple, ie a simplified CSS. Note: This book teach you how to right a LL(1) parser using the recursive-descent algorithm. So, as a sub-exercice, I am building the grammar from what I know of CSS. But I'm stuck on a production that I can't transform in LL(1) : //EBNF block = "{", declaration, {";", declaration}, [";"], "}" //BNF <block> =:: "{" <declaration> "}" <declaration> =:: <single-declaration> <opt-end> | <single-declaration> ";" <declaration> <opt-end> =:: "" | ";" This describe a CSS block. Valid block can have the form : { property : value } { property : value; } { property : value; property : value } { property : value; property : value; } ... The problem is with the optional ";" at the end, because it overlap with the starting character of {";", declaration}, so when my parser meet a semicolon in this context, it doesn't know what to do. The book talk about this problem, but in its example, the semicolon is obligatory, so the rule can be modified like this : block = "{", declaration, ";", {declaration, ";"}, "}" So, Is it possible to achieve what I'm trying to do using a LL(1) parser?

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  • Implementing eval and load functions inside a scripting engine with Flex and Bison.

    - by Simone Margaritelli
    Hy guys, i'm developing a scripting engine with flex and bison and now i'm implementing the eval and load functions for this language. Just to give you an example, the syntax is like : import std.*; load( "some_script.hy" ); eval( "foo = 123;" ); println( foo ); So, in my lexer i've implemented the function : void hyb_parse_string( const char *str ){ extern int yyparse(void); YY_BUFFER_STATE prev, next; /* * Save current buffer. */ prev = YY_CURRENT_BUFFER; /* * yy_scan_string will call yy_switch_to_buffer. */ next = yy_scan_string( str ); /* * Do actual parsing (yyparse calls yylex). */ yyparse(); /* * Restore previous buffer. */ yy_switch_to_buffer(prev); } But it does not seem to work. Well, it does but when the string (loaded from a file or directly evaluated) is finished, i get a sigsegv : Program received signal SIGSEGV, Segmentation fault. 0xb7f2b801 in yylex () at src/lexer.cpp:1658 1658 if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW ) As you may notice, the sigsegv is generated by the flex/bison code, not mine ... any hints, or at least any example on how to implement those kind of functions? PS: I've succesfully implemented the include directive, but i need eval and load to work not at parsing time but execution time (kind of PHP's include/require directives).

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  • using an alternative string quotation syntax in python

    - by Cawas
    Just wondering... I find using escape characters too distracting. I'd rather do something like this: print ^'Let's begin and end with sets of unlikely 2 chars and bingo!'^ Let's begin and end with sets of unlikely 2 chars and bingo! Note the ' inside the string, and how this syntax would have no issue with it, or whatever else inside for basically all cases. Too bad markdown can't properly colorize it (yet), so I decided to <pre> it. Sure, the ^ could be any other char, I'm not sure what would look/work better. That sounds good enough to me, tho. Probably some other language already have a similar solution. And, just maybe, Python already have such a feature and I overlooked it. I hope this is the case. But if it isn't, would it be too hard to, somehow, change Python's interpreter and be able to select an arbitrary (or even standardized) syntax for notating the strings? I realize there are many ways to change statements and the whole syntax in general by using pre-compilators, but this is far more specific. And going any of those routes is what I call "too hard". I'm not really needing to do this so, again, I'm just wondering.

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  • Why does Microsoft advise against readonly fields with mutable values?

    - by Weeble
    In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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  • Encapsulate update method inside of object or have method which accepts an object to update

    - by Tom
    Hi, I actually have 2 questions related to each other: I have an object (class) called, say MyClass which holds data from my database. Currently I have a list of these objects ( List < MyClass ) that resides in a singleton in a "communal area". I feel it's easier to manage the data this way and I fail to see how passing a class around from object to object is beneficial over a singleton (I would be happy if someone can tell me why). Anyway, the data may change in the database from outside my program and so I have to update the data every so often. To update the list of the MyClass I have a method called say, Update, written in another class which accepts a list of MyClass. This updates all the instances of MyClass in the list. However would it be better instead to encapulate the Update() method inside the MyClass object, so instead I would say foreach(MyClass obj in MyClassList) { obj.update(); } What is a better implementation and why? The update method requires a XML reader. I have written an XML reader class which is basically a wrapper over the standard XML reader the language natively provides which provides application specific data collection. Should the XML reader class be in anyway in the "inheritance path" of the MyClass object - the MyClass objects inherits from the XML reader because it uses a few methods. I can't see why it should. I don't like the idea of declaring an instance of the XML Reader class inside of MyClass and an MyClass object is meant to be a simple "record" from the database and I feel giving it loads of methods, other object instances is a bit messy. Perhaps my XML reader class should be static but C#'s native XMLReader isn't static.? Any comments would be greatly appreciated Thanks Thomas

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