Search Results

Search found 22104 results on 885 pages for 'programming language'.

Page 776/885 | < Previous Page | 772 773 774 775 776 777 778 779 780 781 782 783 | Next Page >

How do I make a web interface for a socket server

- by mgroat

I've got a socket server running (it's something that's basically like a chat server). Users can telnet into it, but I'd like to make a web interface. This is the first time I've ever done something like this, so I'm not really sure where to start. A few thoughts I've had: Have some server-side Python (or PHP) on my webserver, which accesses the socket server. I think I know enough about sockets to have Python interact with the server, but how do I go about getting the website that the user sees to update in real time? Should I just have the website refresh few seconds? I would prefer to do things this way if I can figure out how. Write a Java applet that interacts with the socket server, and embed the applet in the website. I would have to re-learn a language that I haven't touched in years, but my main goal here is learning -- so that wouldn't be such a bad thing. The main problem I have with this is that it requires end users to have Java installed on their computers, which I'd rather not do. Is one of these two solutions the right way to go? Anybody know where I can find a good tutorial to get started? Edit: There's no real security concerns with exposing the server to the internet.

Read the article
When to choose which machine learning classifier?

- by LM

Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

Read the article
Javascript problem with location.href.

- by Patrick

Hello! I have a textbox and whenever the user presses a key it's checked to see if the user pressed enter. If the enter key is pressed, i want to add all the info in the textbox and transfer the user to a different url. <script language="javascript" type="text/javascript"> function checkEnter(e){ //e is event object passed from function invocation var characterCode; if(e && e.which){ //if which property of event object is supported (NN4) e = e; characterCode = e.which; //character code is contained in NN4's which property } else{ e = event; characterCode = e.keyCode; //character code is contained in IE's keyCode property } if (characterCode == 13) { //if generated character code is equal to ascii 13 (if enter key) var searchLink = '/Search/?Keywords=' + document.getElementById('<%= searchBox.ClientID %>').value; transferUser(searchLink); return false; } else{ return true; } } function transferUser(url) { window.location.href = url; window.location.replace(url); } </script> Search: <input name="ctl00$searchBox" type="text" id="ctl00_searchBox" class="header_line_search_box_textbox" onKeyPress="checkEnter(event);" /> I have tried every possible combination, but nothing happens. The site just refreshes itself. I also need somehow to convert the text from the user to html safe, must like the HttpUtility.EncodeUrl in aspx.

Read the article
Android: Error trying to edit button text after thread sleep

- by Vass

(programming Android in Eclipse) I am trying to set up a delay in changing the text in a button. I am getting errors only after there is a delay and the text needs to be changed. Here is the simplified code without a while loop: final Button button_target = (Button) findViewById(R.id.button_target); Thread textChange = new Thread(new Runnable() { public void run(){ button_target.setText("fog"); try{ Thread.sleep(3000); }catch(InterruptedException e){} } }); textChange.start(); And now here is the code where a change of text on the button is required after the sleep which now causes and error and exit (forced): final Button button_target = (Button) findViewById(R.id.button_target); Thread textChange = new Thread(new Runnable() { public void run(){ button_target.setText("cat"); try{ Thread.sleep(3000); }catch(InterruptedException e){} button_target.setText("dog"); } }); textChange.start(); what am I doing to cause the error? Is there another method that I should do to be able to invoke a sleep or delay to the thread so that a text change operation can be performed? (the actual code has a while loop but I believe this form puts the error in highlight)

Read the article
How to Implement Overlay blend method using opengles 1.1

- by Cylon

Blow is the algorithm of overlay. and i want using it on iphone, but iphone 3g only support opengles 1.1, can not using glsl. can i using blend function or texture combine to implement it. thank you /////////Reference from OpenGL Shading® Language Third Edition /////////// 19.6.12 Overlay OVERLAY first computes the luminance of the base value. If the luminance value is less than 0.5, the blend and base values are multiplied together. If the luminance value is greater than 0.5, a screen operation is performed. The effect is that the base value is mixed with the blend value, rather than being replaced. This allows patterns and colors to overlay the base image, but shadows and highlights in the base image are preserved. A discontinuity occurs where luminance = 0.5. To provide a smooth transition, we actually do a linear blend of the two equations for luminance in the range [0.45,0.55]. float luminance = dot(base, lumCoeff); if (luminance < 0.45) result = 2.0 * blend * base; else if (luminance 0.55) result = white - 2.0 * (white - blend) * (white - base); else { vec4 result1 = 2.0 * blend * base; vec4 result2 = white - 2.0 * (white - blend) * (white - base); result = mix(result1, result2, (luminance - 0.45) * 10.0); }

Read the article
php when to use get method?

- by user329394

how all, when is the right time to use $_GET['data']? i want to pass value of userid from page A to page B by using popup javascript. $qry="SELECT * FROM dbase WHERE id='".$id."'"; $sql=mysql_query($qry); $rs=mysql_fetch_array($sql); <script language="JavaScript"> function myPopup() { window.open( "<?=$CFG->wwwroot.'/ptk/main.php?task=ptk_checkapp&id='.$rs['userid'];?>" ,"myWindow", "status = 1, height = 500, width = 500, scrollbars=yes,toolbar=no,directories=no,location=no,menubar=no, resizable='yes';" ) } </script> calling by hyperlink: <a href="#" onclick="myPopup()"> <?=ucwords(strtolower($rs->nama));?> </a> It seems that , the $rs['user'] dont hold any value on it. can tell me what problem or may be solution? thank you very much.

Read the article
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.

Read the article
What is the preferred way in C++ for converting a builtin type (int) to bool?

- by Martin

When programming with Visual C++, I think every developer is used to see the warning warning C4800: 'BOOL' : forcing value to bool 'true' or 'false' from time to time. The reason obviously is that BOOL is defined as int and directly assigning any of the built-in numerical types to bool is considered a bad idea. So my question is now, given any built-in numerical type (int, short, ...) that is to be interpreted as a boolean value, what is the/your preferred way of actually storing that value into a variable of type bool? Note: While mixing BOOL and bool is probably a bad idea, I think the problem will inevitably pop up whether on Windows or somewhere else, so I think this question is neither Visual-C++ nor Windows specific. Given int nBoolean; I prefer this style: bool b = nBoolean?true:false; The following might be alternatives: bool b = !!nBoolean; bool b = (nBoolean != 0); Is there a generally preferred way? Rationale? I should add: Since I only work with Visual-C++ I cannot really say if this is a VC++ specific question or if the same problem pops up with other compilers. So it would be interesting to specifically hear from g++ or users how they handle the int-bool case. Regarding Standard C++: As David Thornley notes in a comment, the C++ Standard does not require this behavior. In fact it seems to explicitly allow this, so one might consider this a VC++ weirdness. To quote the N3029 draft (which is what I have around atm.): 4.12 Boolean conversions [conv.bool] A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. (...)

Read the article
How to show a server side error message in a popup using php

- by Fero

Hi all, I found some of the similar questions here but they are all in C#. So kindly tell me the easiest way to show the server side error message using popup. The popup may be anything like thickbox, modalpopup etc... Here is the sample code. I didn't get the error message in the popup. <script type="text/javascript" src="thickbox/jquery-latest.js"></script> <script type="text/javascript" src="thickbox/thickbox.js"></script> <link href="thickbox/thickbox.css" rel="stylesheet" type="text/css" /> <span class="prtexterror" style="color:#FF0000;display:none;" id="hiddenModalContent" >{$error_login}</span> {literal} <script language="javascript" type="text/javascript"> $(document).ready(function() { tb_show("Please, login", "?tb_inline=true&inlineId=hiddenModalContent&height=180&width=300&modal=true", null); }); </script> {/literal} Any other ways are always welcome. thanks in advance

Read the article
Parse usable Street Address, City, State, Zip from a string

- by Rob Allen

Problem: I have an address field from an Access database which has been converted to Sql Server 2005. This field has everything all in one field. I need to parse out the individual sections of the address into their appropriate fields in a normalized table. I need to do this for approximately 4,000 records and it needs to be repeatable. Here are the rules for this exercise: 1 - no whining about how this should have been separate fields in the first place, we are often confronted with less than ideal situations and have to make the best of them 2- for this post, use any language you want 3- feel free to play code golf 4 - Assume an address in the US (for now) 5 - assume that the input string will sometimes contain an addressee (the person being addressed) and/or a second street address (i.e. Suite B) 6 - states may be abbreviated 7 - zip code could be standard 5 digit or zip+4 8 - there are typos in some instances UPDATE: In response to the questions posed, standards were not universally followed, I need need to store the individual values, not just geocode and errors means typo (corrected above) Sample Data: A. P. Croll & Son 2299 Lewes-Georgetown Hwy, Georgetown, DE 19947 11522 Shawnee Road, Greenwood DE 19950 144 Kings Highway, S.W. Dover, DE 19901 Intergrated Const. Services 2 Penns Way Suite 405 New Castle, DE 19720 Humes Realty 33 Bridle Ridge Court, Lewes, DE 19958 Nichols Excavation 2742 Pulaski Hwy Newark, DE 19711 2284 Bryn Zion Road, Smyrna, DE 19904 VEI Dover Crossroads, LLC 1500 Serpentine Road, Suite 100 Baltimore MD 21 580 North Dupont Highway Dover, DE 19901 P.O. Box 778 Dover, DE 19903

Read the article
json parsing problems

- by C.

Hi I have the following Json : "{\"doc\":{\"info\":{\"allowDistribution\":\"true\",\"allowSearch\":\"true\",\"calaisRequestID\":\"67a02f61-7e45-cfc4-1276-e123c5f7422f\",\"externalID\":\"\",\"id\":\"http://id.opencalais.com/dBo1YRiQeqS-kfO-m9UeWA\",\"docId\":\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb\",\"document\":\"What type of music do you listen to? How much would you pay for a cd? Do you still buy cds? Do you like Shakira? What genre of music do you listen to?\",\"docTitle\":\"\",\"docDate\":\"2010-03-17 17:40:41.323\",\"externalMetadata\":\"\",\"submitter\":\"\"},\"meta\":{\"contentType\":\"text/raw\",\"emVer\":\"7.1.1103.5\",\"langIdVer\":\"DefaultLangId\",\"processingVer\":\"CalaisJob01\",\"submitionDate\":\"2010-03-17 17:40:41.183\",\"submitterCode\":\"b54c734e-b865-185b-c83a-66e1c66272de\",\"signature\":\"digestalg-1|FXnvwLovOsqVoSPX0JfGvj3tp7s=|cyV2tZWY9OXG1RBO0SuND4kd3Pkvqv0cS2YpsEBQhXDfSV4KoE61sQ==\",\"language\":\"English\",\"messages\":[]}},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/1\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/EntertainmentCulture\",\"classifierName\":\"Calais\",\"categoryName\":\"Entertainment_Culture\",\"score\":1},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/2\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/HumanInterest\",\"classifierName\":\"Calais\",\"categoryName\":\"Human Interest\",\"score\":1},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/3\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/TechnologyInternet\",\"classifierName\":\"Calais\",\"categoryName\":\"Technology_Internet\",\"score\":0.932}}" Can you please tell me why it won't parse this? This is my code: JObject o = JObject.Parse(json); String category = (string)o["doc"]["_typeGroup"]["categoryName"]; It tells me: Object reference not set to an instance of an object. Thanks :)

Read the article
c++ callback syntax in a class

- by Mr Bell

I am trying to figure out the syntax to register a callback with this 3rd party software. I think it is probably a basic question, I just am not too familiar with c++. They have a method for registering a callback function so their code can call a function in my code when an event happens. They provided a working example that registers the callback from the main file, but I want to know how to do it when working inside a class Their method signature: smHTRegisterHeadPoseCallback(smEngineHandle engine_handle, void *user_data, smHTHeadPoseCallback callback_fun); Working example from the main file: void STDCALL receiveHeadPose(void *,smEngineHeadPoseData head_pose, smCameraVideoFrame video_frame) { ... } void main() { ... smHTRegisterHeadPoseCallback(engine_handle,0,receiveHeadPose) ... } But I want to use this from my class MyClass.h class FaceEngine { public: void STDCALL receiveFaceData(void *, smEngineFaceData face_data, smCameraVideoFrame video_frame); ... MyClass.cpp void FaceEngine::Start(void) { rc = smHTRegisterFaceDataCallback(hFaceAPIEngine,0,&FaceEngine::receiveFaceData); ... Results in this compiler error: Error 1 error C2664: 'smHTRegisterFaceDataCallback' : cannot convert parameter 3 from 'void (__stdcall FaceEngine::* )(void *,smEngineFaceData,smCameraVideoFrame)' to 'smHTFaceDataCallback' d:\stuff\programming\visual studio 2008\projects\tut02_vertices\faceengine.cpp 43 Beard If my question isn't clear please let me know how I can clarify.

Read the article
How to receive Email in JEE application

- by Hank

Obviously it's not so difficult to send out emails from a JEE application via JavaMail. What I am interested in is the best pattern to receive emails (notification bounces, mostly)? I am not interested in IMAP/POP3-based approaches (polling the inbox) - my application shall react to inbound emails. One approach I could think of would be Keep existing MTA (postfix on linux in my case) - ops team already knows how to configure / operate it For every mail that arrives, spawn a Java app that receives the data and sends it off via JMS. I could do this via an entry in /etc/aliases like myuser: "|/path/to/javahelper" with javahelper calling the Java app, passing STDIN along. MDB (part of JEE application) receives JMS message, parses it, detects bounce message and acts accordingly. Another approach could be Open a listening network socket on port 25 on the JEE application container. Associate a SessionBean with the socket. Bean is part of JEE application and can parse/detect bounces/handle the messages directly. Keep existing MTA as inbound relay, do all its security/spam filtering, but forward emails to myuser (that pass the filter) to the JEE application container, port 25. The first approach I have done before (albeit in a different language/setup). From a performance and (perceived) cleanliness point of view, I think the second approach is better, but it would require me to provide a proper SMTP transport implementation. Also, I don't know if it's at all possible to connect a network socket with a bean... What is your recommendation? Do you have details about the second approach?

Read the article
Replacing content with jquery.

- by BillZ

I am loading a movie into a overlay. My problem is that when I close the div overlay the movie continues to play. I do not control the code on the move side it is imported via a script tag which then opens in a iframe. I am able to remove the content of the of the div and then the movie stops playing. Then of course when the user opens the div again the movie is gone. My current thinking was that I could simply replace the script tag with one just like it but the outcome of that is that there is nothing there. I have been using jquery. Thanks -- script -- $(document).ready(function() { $("#closeModal2").click(function() { $("#movieContainer").html("<script src='http://www.accelacast.com/programs/launch.js'/>"); }); }); -- html -- <div id="movieContainer"> <script id="movieTag" language='JavaScript' src='http://www.accelacast.com/programs/launch.js'/> </div> On a side note. I tried replacing the src attribute of the script tag with no luck. I was able to replace the src of a image though. Is it not possible to effect the src attribute of script? Thanks

Read the article
Analyze log files from many languages using a single tool. And recommendations of logging frameworks

- by Binary255

We have a system build on lots of languages. The ones we are interested in logging, in order of priority, are: C/C++ PHP C# Bash Java Wish list: If it is possible, we would like logging to be achieved from the above languages in such a way that we may use a single log viewing tool for all of them. Ideally they would be in the same format, but next to that in as few formats as possible and readable from as many log file viewers as possible. If it is possible logging to a single log file or a set of log files would be nice. With a possibility to filter based on the source language that is being logged. We would like to copy the log files (or should be log to a database and copy it instead?) from multiple servers to a single location. So that we can analyze the log files from many servers at the same time (to see if any of our servers execute a certain piece legacy code for example). Being able to change logging level at runtime would be nice. Thank you for reading! It's quite a complex problem, I hope someone has wrestled with it before and has some valuable information!

Read the article
correct format for function prototype

- by yCalleecharan

Hi, I'm writing to a text file using the following declaration: void create_out_file(char file_name[],long double *z1){ FILE *out; int i; if((out = fopen(file_name, "w+")) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < ARRAY_SIZE; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } Where z1 is an long double array of length ARRAY_SIZE. The calling function is: create_out_file("E:/first67/jz1.txt", z1); I defined the prototype as: void create_out_file(char file_name[], long double z1[]); which I'm putting before "int main" but after the preprocessor directives. My code works fine. I was thinking of putting the prototype as void create_out_file(char file_name[],long double *z1). Is this correct? *z1 will point to the first array element of z1. Is my declaration and prototype good programming practice? Thanks a lot...

Read the article
Site doesn't show up. Instead a bunch of weird characters?

- by Richard Knop

‹?????í˜±jÃ0†w=Å=AÜ ÂÐƒ)ÅKGÅ:¢En%¹©ß¾²Ý 7xèpußøãŸ~ÝöÇ®Ömót¨•îŸû®©îao‚½‘Í:ºR†æk@´huõÃ(];z:¼•Íö¾þ{¥•‚¾ímwi£_±Ä1)–ÄÇ?‡‘,‰%Ž#YKF²Ä²Ä8ŒèKF²$–88ŒdI,qpÉ’Xâà0’%±Ä1Àaþe–TïÆOŒ@ 2^ßÇh"ù¦`Î!ëœ„yœ"Dü˜0e°Ó:ËË>e„ñÊˆfp.à(U®<œv¿ì;xñhRY3˜‹¡?ÞdŒ;Uºõ×R°WkÑ^Z÷¥¯Wß.Ò¤·?? That's exactly what shows up instead of my website in the web browser. Though on localhost the website works great. It's a Zend Framework based website, on localhost the output looks something like this (shortened version): <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>Title</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <meta http-equiv="Content-Language" content="en-US" /> </head> <body>  </body> </html> What could cause this problem? It used to work before, this bug has only appeared today (or maybe already yesterday, I'm not sure).

Read the article
OOP - Handling Automated Instances of a Class - PHP

- by dscher

This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

Read the article
Project euler problem 45

- by Peter

Hi, I'm not yet a skilled programmer but I thought this was an interesting problem and I thought I'd give it a go. Triangle, pentagonal, and hexagonal numbers are generated by the following formulae: Triangle T_(n)=n(n+1)/2 1, 3, 6, 10, 15, ... Pentagonal P_(n)=n(3n-1)/2 1, 5, 12, 22, 35, ... Hexagonal H_(n)=n(2n-1) 1, 6, 15, 28, 45, ... It can be verified that T_(285) = P_(165) = H_(143) = 40755. Find the next triangle number that is also pentagonal and hexagonal. Is the task description. I know that Hexagonal numbers are a subset of triangle numbers which means that you only have to find a number where Hn=Pn. But I can't seem to get my code to work. I only know java language which is why I'm having trouble finding a solution on the net womewhere. Anyway hope someone can help. Here's my code public class NextNumber { public NextNumber() { next(); } public void next() { int n = 144; int i = 165; int p = i * (3 * i - 1) / 2; int h = n * (2 * n - 1); while(p!=h) { n++; h = n * (2 * n - 1); if (h == p) { System.out.println("the next triangular number is" + h); } else { while (h > p) { i++; p = i * (3 * i - 1) / 2; } if (h == p) { System.out.println("the next triangular number is" + h); break; } else if (p > h) { System.out.println("bummer"); } } } } } I realize it's probably a very slow and ineffecient code but that doesn't concern me much at this point I only care about finding the next number even if it would take my computer years :) . Peter

Read the article
High memory usage for dummies

- by zaf

I've just restarted my firefox web browser again because it started stuttering and slowing down. This happens every other day due to (my understanding) of excessive memory usage. I've noticed it takes 40M when it starts and then, by the time I notice slow down, it goes to 1G and my machine has nothing more to offer unless I close other applications. I'm trying to understand the technical reasons behind why its such a difficult problem to sol ve. Mozilla have a page about high memory usage: http://support.mozilla.com/en-US/kb/High+memory+usage But I'm looking for a slightly more in depth and satisfying explanation. Not super technical but enough to give the issue more respect and please the crowd here. Some questions I'm already pondering (they could be silly so take it easy): When I close all tabs, why doesn't the memory usage go all the way down? Why is there no limits on extensions/themes/plugins memory usage? Why does the memory usage increase if it's left open for long periods of time? Why are memory leaks so difficult to find and fix? App and language agnostic answers also much appreciated.

Read the article
What is wrong with accessing DBI directly?

- by canavanin

Hi everyone! I'm currently reading Effective Perl Programming (2nd edition). I have come across a piece of code which was described as being poorly written, but I don't yet understand what's so bad about it, or how it should be improved. It would be great if someone could explain the matter to me. Here's the code in question: sub sum_values_per_key { my ( $class, $dsn, $user, $password, $parameters ) = @_; my %results; my $dbh = DBI->connect( $dsn, $user, $password, $parameters ); my $sth = $dbh->prepare( 'select key, calculate(value) from my_table'); $sth->execute(); # ... fill %results ... $sth->finish(); $dbh->disconnect(); return \%results; } The example comes from the chapter on testing your code (p. 324/325). The sentence that has left me wondering about how to improve the code is the following: Since the code was poorly written and accesses DBI directly, you'll have to create a fake DBI object to stand in for the real thing. I have probably not understood a lot of what the book has so far been trying to teach me, or I have skipped the section relevant for understanding what's bad practice about the above code... Well, thanks in advance for your help!

Read the article
Drag and Drop in Silverlight with F# and Asynchronous Workflows

- by knotig

Hello everyone! I'm trying to implement drag and drop in Silverlight using F# and asynchronous workflows. I'm simply trying to drag around a rectangle on the canvas, using two loops for the the two states (waiting and dragging), an idea I got from Tomas Petricek's book "Real-world Functional Programming", but I ran into a problem: Unlike WPF or WinForms, Silverlight's MouseEventArgs do not carry information about the button state, so I can't return from the drag-loop by checking if the left mouse button is no longer pressed. I only managed to solve this by introducing a mutable flag. Would anyone have a solution for this, that does not involve mutable state? Here's the relevant code part (please excuse the sloppy dragging code, which snaps the rectangle to the mouse pointer): type MainPage() as this = inherit UserControl() do Application.LoadComponent(this, new System.Uri("/SilverlightApplication1;component/Page.xaml", System.UriKind.Relative)) let layoutRoot : Canvas = downcast this.FindName("LayoutRoot") let rectangle1 : Rectangle = downcast this.FindName("Rectangle1") let mutable isDragged = false do rectangle1.MouseLeftButtonUp.Add(fun _ -> isDragged <- false) let rec drag() = async { let! args = layoutRoot.MouseMove |> Async.AwaitEvent if (isDragged) then Canvas.SetLeft(rectangle1, args.GetPosition(layoutRoot).X) Canvas.SetTop(rectangle1, args.GetPosition(layoutRoot).Y) return! drag() else return() } let wait() = async { while true do let! args = Async.AwaitEvent rectangle1.MouseLeftButtonDown isDragged <- true do! drag() } Async.StartImmediate(wait()) () Thank you very much for your time!

Read the article
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.

Read the article
Private member vector of vector dynamic memory allocation

- by Geoffroy

Hello, I'm new to C++ (I learned programming with Fortran), and I would like to allocate dynamically the memory for a multidimensional table. This table is a private member variable : class theclass{ public: void setdim(void); private: std::vector < std::vector <int> > thetable; } I would like to set the dimension of thetable with the function setdim(). void theclass::setdim(void){ this->thetable.assign(1000,std::vector <int> (2000)); } I have no problem compiling this program, but as I execute it, I've got a segmentation fault. The strange thing for me is that this piece (see under) of code does exactly what I want, except that it doesn't uses the private member variable of my class : std::vector < std::vector < int > > thetable; thetable.assign(1000,std::vector <int> (2000)); By the way, I have no trouble if thetable is a 1D vector. In theclass : std::vector < int > thetable; and if in setdim : this->thetable.assign(1000,2); So my question is : why is there such a difference with "assign" between thetable and this-thetable for a 2D vector? And how should I do to do what I want? Thank-you for your help, Best regards, -- Geoffroy

Read the article
How to access hidden template in unnamed namespace?

- by Johannes Schaub - litb

Here is a tricky situation, and i wonder what ways there are to solve it namespace { template <class T> struct Template { /* ... */ }; } typedef Template<int> Template; Sadly, the Template typedef interferes with the Template template in the unnamed namespace. When you try to do Template<float> in the global scope, the compiler raises an ambiguity error between the template name and the typedef name. You don't have control over either the template name or the typedef-name. Now I want to know whether it is possible to: Create an object of the typedefed type Template (i.e Template<int>) in the global namespace. Create an object of the type Template<float> in the global namespace. You are not allowed to add anything to the unnamed namespace. Everything should be done in the global namespace. This is out of curiosity because i was wondering what tricks there are for solving such an ambiguity. It's not a practical problem i hit during daily programming.

Read the article

< Previous Page | 772 773 774 775 776 777 778 779 780 781 782 783 | Next Page >