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  • Initialize Static Array of Structs in C

    - by russell_h
    I implementing a card game in C. There are lots of types of cards and each has a bunch of information, including some actions that will need to be individually scripted associated with it. Given a struct like this (and I'm not certain I have the syntax right for the function pointer) struct CARD { int value; int cost; // This is a pointer to a function that carries out actions unique // to this card int (*do_actions) (struct GAME_STATE *state, int choice1, int choice2); }; I would like to initialize a static array of these, one for each card. I'm guessing this would look something like this int do_card0(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } int do_card1(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } extern static struct cardDefinitions[] = { {0, 1, do_card0}, {1, 3, do_card1} }; Will this work, and am I going about this the right way at all? I'm trying to avoid huge numbers of switch statements. Do I need to define the 'do_cardN' functions ahead of time, or is there some way to define them inline in the initialization of the struct (something like a lambda function in python)? I'll need read-only access to cardDefinitions from a different file - is 'extern static' correct for that? I know this is a lot of questions rolled into one but I'm really a bit vague about how to go about this. Thanks.

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  • A GUID as the MySQL table's Primary Key or as a separate column

    - by Ben
    I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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  • Understanding how software testing works and what to test.

    - by RHaguiuda
    Intro: I've seen lots of topics here on SO about software testing and other terms I don't understand. Problem: As a beginner developer I, unfortunately, have no idea how software testing works, not even how to test a simple function. This is a shame, but thats the truth. I also hope this question can help others beginners developers too. Question: Can you help me to understand this subject a little bit more? Maybe some questions to start would help: When I develop a function, how should I test it? For example: when working with a sum function, should I test every input value possible or just some limits? How about testing functions with strings as parameters? In a big program, do I have to test every single piece of code of it? When you guys program do you test every code written? How automated test works and how can I try one? How tools for automated testing works and what they do? I`ve heard about unit testing. Can I have a brief explanation on this? What is a testing framework? If possible please post some code with examples to clarify the ideas. Any help on this topic is very welcome! Thanks.

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  • Compact data structure for storing a large set of integral values

    - by Odrade
    I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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  • What are some methods to prevent double posting in a form? (PHP)

    - by jpjp
    I want to prevent users from accidentally posting a comment twice. I use the PRG (post redirect get) method, so that I insert the data on another page then redirect the user back to the page which shows the comment. This allows users to refresh as many times as they want. However this doesn't work when the user goes back and clicks submit again or when they click submit 100 times really fast. I don't want 100 of the same comments. I looked at related questions on SO and found that a token is best. But I am having trouble using it. //makerandomtoken(20) returns a random 20 length char. <form method="post" ... > <input type="text" id="comments" name="comments" class="commentbox" /><br/> <input type="hidden" name="_token" value="<?php echo $token=makerandomtoken(20); ?>" /> <input type="submit" value="submit" name="submit" /> </form> if (isset($_POST['submit']) && !empty($comments)) { $comments= mysqli_real_escape_string($dbc,trim($_POST['comments'])); //how do I make the if-statment to check if the token has been already set once? if ( ____________){ //don't insert comment because already clicked submit } else{ //insert the comment into the database } } So I have the token as a hidden value, but how do I use that to prevent multiple clicking of submit. METHODS: someone suggested using sessions. I would set the random token to $_SESSION['_token'] and check if that session token is equal to the $_POST['_token'], but how do I do that? When I tried, it still doesn't check

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  • how i can retrive files from folder on hard-disk and how to display uplaoded file data into a textar

    - by Deepak Narwal
    I have made a application form in which i am asking for username,password,email id and user's resume.Now after uploading resume i am storing it into hard disk into htdocs/uploadedfiles/..in a format something like this username_filename.In database i am storing file name,file size,file type.Some coading for this i am showing here $filesize=$_FILES['file']['size']; $filename=$_FILES['file']['name']; $filetype=$_FILES['file']['type']; $temp_name=$_FILES['file']['tmp_name']; //temporary name of uploaded file $pwd_hash = hash('sha1',$_POST['password']); $target_path = "uploadedfiles/"; $target_path = $target_path.$_POST['username']."_".basename( $_FILES['file']['name']); move_uploaded_file($_FILES['file']['tmp_name'], $target_path) ; $sql="insert into employee values ('NULL','{$_POST[username]}','{$pwd_hash}','{$filename}','{$filetype}','$filesize',NOW())"; Now i have two questions 1.NOw how i can display this file data into a textarea(something like naukri.com resume section) 2.How one can retrive that resume file from folder on hard-disk.What query should i write to fetch this file from that folder.I know how to retrive data from database but i dont know how to retrive data from a folder in hard-disk like in the case if user want to delete this file or he wnat to download this file.How i can do this

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  • Windows loader problem - turn on verbose mode

    - by doobop
    Hi, I'm in the process of reorganizing some of the legacy libraries in our application which has unmanaged code calling into libraries of managed code. While I have the code reorganized, it produces the following loader error: ... 'app.exe': Loaded 'C:\WINDOWS\system32\CsDisp.dll' 'app.exe': Loaded 'C:\WINDOWS\system32\psapi.dll' 'app.exe': Loaded 'C:\WINDOWS\system32\shell32.dll' 'app.exe': Loaded 'C:\appCode\Debug\daq206_32.dll', Binary was not built with debug information. 'app.exe': Loaded 'C:\appCode\Debug\SiUSBXp.dll', Binary was not built with debug information. 'app.exe': Loaded 'C:\appCode\Debug\AdlinkDAQ.dll', Symbols loaded. 'app.exe': Loaded 'C:\WINDOWS\system32\P9842.dll', Binary was not built with debug information. LDR: LdrRelocateImageWithBias() failed 0xc0000018 LDR: OldBase : 10000000 LDR: NewBase : 00A80000 LDR: Diff : 0x7c90d6fa0012f6cc LDR: NextOffset : 00000000 LDR: *NextOffset : 0x0 LDR: SizeOfBlock : 0xa80000 Debugger:: An unhandled non-continuable exception was thrown during process load I believe 0xc0000018 error is an overlapping address range. So, I have two questions. First, what linker options may cause this error? I'm currently linking with /DYNAMICBASE:NO and /FIXED:No as this was how some of the previous libraries were set up. Second, is there a way to turn on verbose mode for the loader so I can see what exactly it's trying to load? P9842 is a third party library so I imagine it is getting to one of my libraries after P9842 and failing on that one. Can I narrow it down? Thanks.

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  • Rails - Help scoring an online quiz in RoR

    - by ChrisWesAllen
    I'm trying to grade a quiz application I would like to make. I have a questions model with and ask(the actual question), 4 choices(a-d), and a correct answer(string). In the view I have the 4 question being diplayed then the correct answer choice (This is just a test for functionality) and then I created a text_field to accept the users answer choice and a button to refresh the index action which has the scoring logic, for now.. --Do I need to put the text_field within a form_tag? <p>1. <%= h @question.q1 %></p> <p>2. <%= h @question.q2 %></p> <p>3. <%= h @question.q3 %></p> <p>4. <%= h @question.q4 %></p> <p>Answer: <%= h @question.correct %></p> <%= text_field_tag :choice, params[:choice] %> <%= button_to "Grade", {:controller => 'site', :action => "index"} %> <p> <%= @answer %></p> Heres the index controller action def index @question = Question.find(1) if @question.correct == params[:choice] @answer = 'right' else @answer = 'wrong' end end Its not really working. The textfield is supposed to take a letter choice like 'a' or 'c' and compare it with the correct answer in the database. I would love this to work by radiobuttons, but I'm a newbie to rails so I thought I'd take baby steps. So if anyone can help me with how to fix this by string, or preferably by radiobuttons, I'd really appreciate it.

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  • Something about Stream

    - by sforester
    I've been working on something that make use of streams and I found myself not clear about some stream concepts( you can also view another question posted by me at http://stackoverflow.com/questions/2933923/about-redirected-stdout-in-system-diagnostics-process ). 1.how do you indicate that you have finished writing a stream, writing something like a EOF? 2.follow the previous question, if I have written a EOF(or something like that) to a stream but didn't close the stream, then I want to write something else to the same stream, can I just start writing to it and no more set up required? 3.if a procedure tries to read a stream(like the stdin ) that no one has written anything to it, the reading procedure will be blocked,finally some data arrives and the procedure will just read till the writing is done,which is indicated by getting a return of 0 count of bytes read rather than being blocked, and now if the procedure issues another read to the same stream, it will still get a 0 count and return immediately while I was expecting it will be blocked since no one is writing to the stream now. So does the stream holds different states when the stream is opened but no one has written to it yet and when someone has finished a writing session? I'm using Windows the .net framework if there will by any thing platform specific. Thanks a lot!

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  • Start developing a database application using Oracle + Net Beans

    - by Ranhiru
    I have thought of creating my first database application for one of my projects using Oracle and Java. I have chosen Netbeans as my development environment. I have a few questions to getting started. Please bare with me as I'm a complete beginner to Oracle + Netbeans This will be a data intensive (yet still for a college project) database application. I do not need 1000 user concurrency or any other very advanced features but basic stuff such as triggers, stored procedures etc. Will the 11g "Express" (XE) suffice for my requirements? Do i need any Java to Oracle bridge (database connectivity driver eg. ODBC etc) for Netbeans to connect to the oracle database? If yes, what are they? Does Netbeans support Oracle databases natively? Any easy to follow guide on how do i connect to the database and insert/retrieve/display data on a J2SE application? (I know that i should Google this but if there's any guide previously followed by anyone and is considered easy, it would be greatly appreciated.)

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  • What are the lengths/limits C preprocessor as a language creation tool? Where can I learn more about

    - by Weston C
    In his FAQ @ http://www2.research.att.com/~bs/bs_faq.html#bootstrapping, Bjarne Stroustrup says: To build [Cfront, the first C++ compiler], I first used C to write a "C with Classes"-to-C preprocessor. "C with Classes" was a C dialect that became the immediate ancestor to C++... I then wrote the first version of Cfront in "C with Classes". When I read this, it piqued my interest in the C preprocessor. I'd seen its macro capabilities as suitable for simplifying common expressions but hadn't thought about its ability to significantly add to syntax and semantics on the level that I imagine bringing classes to C took. So now I have a couple of questions on my mind: 1) Are there other examples of this approach to bootstrapping a language off of C? 2) Is the source to Stroustrup's original work available anywhere? 3) Where could I learn more about the specifics of utilizing this technique? 4) What are the lengths/limits of that approach? Could one, say, create a set of preprocessor macros that let someone write in something significantly Lisp/Scheme like?

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  • Rename files and directories using substitution and variables

    - by rednectar
    I have found several similar questions that have solutions, except they don't involve variables. I have a particular pattern in a tree of files and directories - the pattern is the word TEMPLATE. I want a script file to rename all of the files and directories by replacing the word TEMPLATE with some other name that is contained in the variable ${newName} If I knew that the value of ${newName} was say "Fred lives here", then the command find . -name '*TEMPLATE*' -exec bash -c 'mv "$0" "${0/TEMPLATE/Fred lives here}"' {} \; will do the job However, if my script is: newName="Fred lives here" find . -name '*TEMPLATE*' -exec bash -c 'mv "$0" "${0/TEMPLATE/${newName}}"' {} \; then the word TEMPLATE is replaced by null rather than "Fred lives here" I need the "" around $0 because there are spaces in the path name, so I can't do something like: find . -name '*TEMPLATE*' -exec bash -c 'mv "$0" "${0/TEMPLATE/"${newName}"}"' {} \; Can anyone help me get this script to work so that all files and directories that contain the word TEMPLATE have TEMPLATE replaced by whatever the value of ${newName} is eg, if newName="A different name" and a I had directory of /foo/bar/some TEMPLATE directory/with files then the directory would be renamed to /foo/bar/some A different name directory/with files and a file called some TEMPLATE file would be renamed to some A different name file

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  • Bulletin board - Database optimisation

    - by andrew
    This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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  • Request size limitation when using MultipartHttpServletRequest of Spring 3.0

    - by Spiderman
    I'd like to know what is the size limitation if I upload list of files in one client's form submition using HTTP multipart content type. On the server side I am using Spring's MultipartHttpServletRequest to handle the request. mM questions: Is there should be different file size limitation and total request size limitation or file size is the only limitation and the request is capable of uploading 100s of files as lonng as they are not too large. Doest the Spring request wrapper read the complete request and store it in the JAVA heap memory or it store temporaray files of it to be able to use big quota. Is the use of reading the httpservlet request in streaming would change the size limitation than using complete http request read at-once by the application server. What is the bottleneck of this process - Java heap size, the quota of the filesystem on which my web-server runs, the maximum allowed BLOB size that the DataBase in which I am gonna save the file alows? or Spring internal limitations? Related threads that still don't have exact answer to this: does-spring-framework-support-streaming-mode-in-mutlipart-requests is-there-a-way-to-get-raw-http-request-stream-from-java-servlet-handler how-to- drop-body-of-a-request-after-checking-headers-in-servlet apache-commons-fileupload-throws-malformedstreamexception

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  • Event handler triggered twice instead of once

    - by kwokwai
    Hi all, I am sorry that I have asked two questions in a few minutes. In a html file, I got three child DIV tags in a parent DIV tag: <div id="container"> <div id="frag-123">123</div> <div id="frag-124">124</div> <div id="frag-125">125</div> </div> Now when I click either the three child DIV tags, I will see two alert boxes pop up instead of one: The first alert box will show something like this: frag-123, and the second alert box will show something like this: container I dont know why. I just want to get the ID value of a child DIV, not the one from the parent DIV. <script> $(function() { $("div").click(function() { var imgID = this.id; alert(imgID); }); }); </script> Please help.

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  • How to write this snippet in Python?

    - by morpheous
    I am learning Python (I have a C/C++ background). I need to write something practical in Python though, whilst learning. I have the following pseudocode (my first attempt at writing a Python script, since reading about Python yesterday). Hopefully, the snippet details the logic of what I want to do. BTW I am using python 2.6 on Ubuntu Karmic. Assume the script is invoked as: script_name.py directory_path import csv, sys, os, glob # Can I declare that the function accepts a dictionary as first arg? def getItemValue(item, key, defval) return !item.haskey(key) ? defval : item[key] dirname = sys.argv[1] # declare some default values here weight, is_male, default_city_id = 100, true, 1 # fetch some data from a database table into a nested dictionary, indexed by a string curr_dict = load_dict_from_db('foo') #iterate through all the files matching *.csv in the specified folder for infile in glob.glob( os.path.join(dirname, '*.csv') ): #get the file name (without the '.csv' extension) code = infile[0:-4] # open file, and iterate through the rows of the current file (a CSV file) f = open(infile, 'rt') try: reader = csv.reader(f) for row in reader: #lookup the id for the code in the dictionary id = curr_dict[code]['id'] name = row['name'] address1 = row['address1'] address2 = row['address2'] city_id = getItemValue(row, 'city_id', default_city_id) # insert row to database table finally: f.close() I have the following questions: Is the code written in a Pythonic enough way (is there a better way of implementing it)? Given a table with a schema like shown below, how may I write a Python function that fetches data from the table and returns is in a dictionary indexed by string (name). How can I insert the row data into the table (actually I would like to use a transaction if possible, and commit just before the file is closed) Table schema: create table demo (id int, name varchar(32), weight float, city_id int); BTW, my backend database is postgreSQL

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  • Can I commit changes to actual database while debugging C# in Visual Studio?

    - by nathant23
    I am creating a C# application using Visual Studio that uses an SQLExpress database. When I hit f5 to debug the application and make changes to the database I believe what is happening is there is a copy of the database in the bin/debug folder that changes are being made to. However, when I stop the debugging and then hit f5 the next time a new copy of the database is being put in the bin/debug folder so that all the changes made the last time are gone. My question is: Is there a way that when I am debugging the application I can have it make changes to the actual database and those changes are actually saved or will it only make changes to the copy in the bin/debug folder (if that is what is actually happening)? I've seen similar questions, but I couldn't find an answer that said if it's possible to make those changes persistent in the actual .mdf file. The reason I ask is because as I build this application I am continuously adding pieces and testing to make sure they all work together. When I put in test data I am using actual data that I would like to stay in the database. This would just help me not have to reenter the data later. Thanks in advance for any help or information that could help me better understand the process.

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  • Python: Serial Transmission

    - by Silent Elektron
    I have an image stack of 500 images (jpeg) of 640x480. I intend to make 500 pixels (1st pixels of all images) as a list and then send that via COM1 to FPGA where I do my further processing. I have a couple of questions here: How do I import all the 500 images at a time into python and how do i store it? How do I send the 500 pixel list via COM1 to FPGA? I tried the following: Converted the jpeg image to intensity values (each pixel is denoted by a number between 0 and 255) in MATLAB, saved the intensity values in a text file, read that file using readlines(). But it became too cumbersome to make the intensity value files for all the 500 images! Used NumPy to put the read files in a matrix and then pick the first pixel of all images. But when I send it, its coming like: [56, 61, 78, ... ,71, 91]. Is there a way to eliminate the [ ] and , while sending the data serially? Thanks in Advance! :)

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  • Java Script in Rails 3.1 works only in certain parts. Any idea why?

    - by Sergio Nekora
    This might seem a bit weird, but since I am new in RoR and cannot find any similar questions I thought you might know. The situation is that JavaScript does not work throughout my whole site. For instance. For the sake of checking, I place a link with an alert function in the footer. It did not work at the beginning, it felt like the JS was disabled(but it wasn't). But eventually it worked. Now it works in most the pages but it does not work in one that there is also an 'autocomplete' field. Of course, this autocomplete field does not work either. That could lead you to think that there is something wrong with the autocomplete code. However this same code is working in the sidebar. Any ideas why? Could it have anything to do with the fact that one day my assets folder appeared empty? After installing the gmaps4rails gem I realized that all my Js and CSS files were gone from my assests folder. Ok, it might have happened long before and I just realized at that point. I don't really know. Here in the root you can see that the 'Hola sip' click at the button works. here it works However, here same link does not trigger the alert function. here it doesn't

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  • iPhone Apps, Objective C, a Graph, and Functions vs. Objects (or something like that)

    - by BillEccles
    Gentleones, I've got a UIImageView that I have in a UIView. This particular UIImageView displays a PNG of a graph. It's important for this particular view controller and another view controller to know what the graph "looks like," i.e., the function described by the PNG graph. These other view controllers need to be able to call a "function" of some sort with the X value returning the Y value. Please ignore the fact (from an outsider's perspective) that I could probably generate the graph programmatically. So my questions are: 1 - Where should I put this function? Should it go in one view controller or the other, or should it go in its own class or main or...? 2 - Should it be an object in some way? Or should it be a straight function? (In either case, where's it belong?) Pardon the apparent n00b-iness of the question. It's 'cause I'm honestly a n00b! This OOP stuff is giving my head a spin having been a procedural programmer for 30 years. (And I choose to learn it by jumping into an iPhone app. Talk about baptism by fire!) Thanks in advance,Bill

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  • CORBA on MacOS X (Cocoa)

    - by user8472
    I am currently looking into different ways to support distributed model objects (i.e., a computational model that runs on several different computers) in a project that initially focuses on MacOS X (using Cocoa). As far as I know there is the possibility to use the class cluster around NSProxy. But there also seem to be implementations of CORBA around with Objective-C support. At a later time there may be the need to also support/include Windows machines. In that case I would need to use something like Gnustep on the Windows side (which may be an option, if it works well) or come up with a combination of both technologies. Or write something manually (which is, of course, the least desirable option). My questions are: If you have experience with both technologies (Cocoa native infrastructure vs. CORBA) can you point out some key features/issues of either approach? Is it possible to use Gnustep with Cocoa in the way explained above? Is it possible (and reasonably feasible, i.e. simpler than writing a network layer manually) to communicate among all MacOS clients using Cocoa's technology and with Windows clients through CORBA?

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  • How would you implement a hashtable in language x?

    - by mk
    The point of this question is to collect a list of examples of hashtable implementations using arrays in different languages. It would also be nice if someone could throw in a pretty detailed overview of how they work, and what is happening with each example. Edit: Why not just use the built in hash functions in your specific language? Because we should know how hash tables work and be able to implement them. This may not seem like a super important topic, but knowing how one of the most used data structures works seems pretty important to me. If this is to become the wikipedia of programming, then these are some of the types of questions that I will come here for. I'm not looking for a CS book to be written here. I could go pull Intro to Algorithms off the shelf and read up on the chapter on hash tables and get that type of info. More specifically what I am looking for are code examples. Not only for me in particular, but also for others who would maybe one day be searching for similar info and stumble across this page. To be more specific: If you had to implement them, and could not use built-in functions, how would you do it? You don't need to put the code here. Put it in pastebin and just link it.

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  • Learning libraries without books or tutorials

    - by Kawili-wili
    While many ask questions about where to find good books or tutorials, I'd like to take the opposite tack. I consider myself to be an entry-level programmer ready to move up to mid-level. I have written code in c, c++, c#, perl, python, clojure, vb, and java, so I'm not completely clueless. Where I see a problem in moving to the next level is learning to make better use of the literally hundreds upon hundreds of libraries available out there. I seem paralyzed unless there is a specific example in a book or tutorial to hand-hold me, yet I often read in various forums where another programmer attempts to assist with a question. He/she will look through the docs or scan the available classes/methods in their favorite IDE and seem to grok what's going on in a relatively short period of time, even if they had no previous experience with that specific library or function. I yearn to break the umbilical chord of constantly spending hour upon hour searching and reading, searching and reading, searching and reading. Many times there is no book or tutorial, or if there is, the discussion glosses over my specific needs or the examples shown are too far off the path for the usage I had in mind or the information is outdated and makes use of deprecated components or the library itself has fallen out of mainstream, yet is still perfectly usable (but no docs, books, or tutorials to hand-hold). My question is: In the absence of books or tutorials, what is the best way to grok new or unfamiliar libraries? I yearn to slicken the grok path so I can get down to the business of doing what I love most -- coding.

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  • Entity Framework 4 + POCO with custom classes and WCF contracts (serialization problem)

    - by eman
    Yesterday I worked on a project where I upgraded to Entity Framework 4 with the Repository pattern. In one post, I have read that it is necessary to turn off the custom tool generator classes and then write classes (same like entites) by hand. That I can do it, I used the POCO Entity Generator and then deleted the new generated files .tt and all subordinate .cs classes. Then I wrote the "entity classes" by myself. I added the repository pattern and implemented it in the business layer and then implemented a WCF layer, which should call the methods from the business layer. By calling an Insert (Add) method from the presentation layer and everything is OK. But if I call any method that should return some class, then I get an error like (the connection was interrupted by the server). I suppose there is a problem with the serialization or am I wrong? How can by this problem solved? I'm using Visual Studio S2010, Entity Framework 4, C#. UPDATE: I have uploaded the project and hope somebody can help me! link text UPDATE 2: My questions: Why is POCO good (pros/cons)? When should POCO be used? Is POCO + the repository pattern a good choice? Should POCO classes by written by myself or could I use auto generated POCO classes?

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  • How do I optimize this postfix expression tree for speed?

    - by Peter Stewart
    Thanks to the help I received in this post: I have a nice, concise recursive function to traverse a tree in postfix order: deque <char*> d; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } d.push_front(cargo); return; }; This is an expression tree. The branch nodes are operators randomly selected from an array, and the leaf nodes are values or the variable 'x', also randomly selected from an array. char *values[10]={"1.0","2.0","3.0","4.0","5.0","6.0","7.0","8.0","9.0","x"}; char *ops[4]={"+","-","*","/"}; As this will be called billions of times during a run of the genetic algorithm of which it is a part, I'd like to optimize it for speed. I have a number of questions on this topic which I will ask in separate postings. The first is: how can I get access to each 'cargo' as it is found. That is: instead of pushing 'cargo' onto a deque, and then processing the deque to get the value, I'd like to start processing it right away. I don't yet know about parallel processing in c++, but this would ideally be done concurrently on two different processors. In python, I'd make the function a generator and access succeeding 'cargo's using .next(). But I'm using c++ to speed up the python implementation. I'm thinking that this kind of tree has been around for a long time, and somebody has probably optimized it already. Any Ideas? Thanks

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