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  • Ruby on Rails ActiveRecord/Include/Associations can't get my query to work

    - by Cypher
    I just started learning Rails and I'm just trying to set up query via associations. All the queries I try to write seem to be doing bizzare things and end up trying to query two tables parsed together with an '_' as one table. I have no clue why this would ever happen My tables are as follows: schools: id name variables: id name type var_entries: id variable_id entry school_entries: id school_id var_entry_id my rails association tables are $local = { :adapter => "mysql", :host => "localhost", :port => "3306".to_i, :database => "spy_2", :username =>"root", :password => "vertrigo" } class School < ActiveRecord::Base establish_connection $local has_many :school_entries has_many :var_entries, :through => school_entries end class Variable < ActiveRecord::Base establish_connection $local has_many :var_entries has_many :school_entries, :through => :var_entries end class VarEntry < ActiveRecord::Base establish_connection $local has_many_and_belongs_to :school_entries belongs_to :variables end class SchoolEntry < ActiveRecord::Base establish_connection $local belongs_to :school has_many :var_entries end I want to do this sql query: SELECT school_id, variable_id,rank FROM school_entries, variables, var_entries, schools WHERE var_entries.variable_id = variables.id AND school_entries.var_entry_id = var_entries.id AND schools.id = school_entries.school_id AND variables.type = 'number'; and put it into Rails notation: here is one of my many failed attempts schools = VarEntry.all(:include => [:school_entries, :variables], :conditions => "variables.type = 'number'") the error: 'const_missing': uninitialized constant VarEntry::Variables (NameError) if i remove variables schools = VarEntry.all(:include => [:school_entries, :variables], :conditions => "type = 'number'") the error is: Mysql::Error: Unkown column 'type' in 'where clause': SELECT * FROM 'var_entries' WHERE (type=number) (ActiveRecord::StatementInvalid) Can anyone tell me where I'm going horribly wrong?

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  • What's the fastest way to bulk insert a lot of data in SQL Server (C# client)

    - by Andrew
    I am hitting some performance bottlenecks with my C# client inserting bulk data into a SQL Server 2005 database and I'm looking for ways in which to speed up the process. I am already using the SqlClient.SqlBulkCopy (which is based on TDS) to speed up the data transfer across the wire which helped a lot, but I'm still looking for more. I have a simple table that looks like this: CREATE TABLE [BulkData]( [ContainerId] [int] NOT NULL, [BinId] [smallint] NOT NULL, [Sequence] [smallint] NOT NULL, [ItemId] [int] NOT NULL, [Left] [smallint] NOT NULL, [Top] [smallint] NOT NULL, [Right] [smallint] NOT NULL, [Bottom] [smallint] NOT NULL, CONSTRAINT [PKBulkData] PRIMARY KEY CLUSTERED ( [ContainerIdId] ASC, [BinId] ASC, [Sequence] ASC )) I'm inserting data in chunks that average about 300 rows where ContainerId and BinId are constant in each chunk and the Sequence value is 0-n and the values are pre-sorted based on the primary key. The %Disk time performance counter spends a lot of time at 100% so it is clear that disk IO is the main issue but the speeds I'm getting are several orders of magnitude below a raw file copy. Does it help any if I: Drop the Primary key while I am doing the inserting and recreate it later Do inserts into a temporary table with the same schema and periodically transfer them into the main table to keep the size of the table where insertions are happening small Anything else? -- Based on the responses I have gotten, let me clarify a little bit: Portman: I'm using a clustered index because when the data is all imported I will need to access data sequentially in that order. I don't particularly need the index to be there while importing the data. Is there any advantage to having a nonclustered PK index while doing the inserts as opposed to dropping the constraint entirely for import? Chopeen: The data is being generated remotely on many other machines (my SQL server can only handle about 10 currently, but I would love to be able to add more). It's not practical to run the entire process on the local machine because it would then have to process 50 times as much input data to generate the output. Jason: I am not doing any concurrent queries against the table during the import process, I will try dropping the primary key and see if that helps. ~ Andrew

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  • Iterator performance contract (and use on non-collections)

    - by polygenelubricants
    If all that you're doing is a simple one-pass iteration (i.e. only hasNext() and next(), no remove()), are you guaranteed linear time performance and/or amortized constant cost per operation? Is this specified in the Iterator contract anywhere? Are there data structures/Java Collection which cannot be iterated in linear time? java.util.Scanner implements Iterator<String>. A Scanner is hardly a data structure (e.g. remove() makes absolutely no sense). Is this considered a design blunder? Is something like PrimeGenerator implements Iterator<Integer> considered bad design, or is this exactly what Iterator is for? (hasNext() always returns true, next() computes the next number on demand, remove() makes no sense). Similarly, would it have made sense for java.util.Random implements Iterator<Double>? Should a type really implement Iterator if it's effectively only using one-third of its API? (i.e. no remove(), always hasNext())

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  • php $_FILES error code returning an unexpected error

    - by EmmyS
    I have some code that allows users to upload multiple files at once. It was never getting to a specific point after the upload, so I put in an echo to test for the value of the error code, and it's returning a value that I'm not sure I understand. Here's the code: $tmpTarget = PCBUG_UPLOADPATH; foreach ($_FILES["attachments"]["error"] as $key => $error) { if ($error == UPLOAD_ERR_OK) { $tmp_name = $_FILES["attachments"]["tmp_name"][$key]; $name = str_replace(" ", "_", $_FILES["attachments"]["name"][$key]); move_uploaded_file($tmp_name, "$tmpTarget/$name"); @unlink($_FILES["attachments"]["tmp_name"][$key]); } else { $errorFlag = true; echo "error = $error"; exit; } } The code that creates the attachments field looks like this: for($i=1; $i<=$max_no_img; $i++){ echo "<input type=file name='attachments[]' class='bginput'><br />"; } where $max_no_img is a variable set further up in the code, and PCBUG_UPLOAD path is a constant defined in an included file. Here's what's confusing: after I submit my form, I go and look in my uploads directory, and the files I've selected through the form are there - they uploaded correctly. However, the code is jumping into the else clause and $error is returning 4, which the php manual indicates means that no file was uploaded. Any ideas? The files very clearly are getting where they're supposed to. Is there some other definition of "uploaded" that isn't happening?

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  • java Properties - to expose or not to expose?

    - by ring bearer
    This might be an age old problem and I am sure everyone has their own ways. Suppose I have some properties defined such as secret.user.id=user secret.password=password website.url=http://stackoverflow.com Suppose I have 100 different classes and places where I need to use these properties. Which one is good (1) I create a Util class that will load all properties and serve them using a key constant Such as : Util is a singleton that loads all properties and keeps up on getInstance() call. Util myUtil = Util.getInstance(); String user = myUtil.getConfigByKey(Constants.SECRET_USER_ID); String password = myUtil.getConfigByKey(Constants.SECRET_PASSWORD); .. //getConfigByKey() - inturns invokes properties.get(..) doSomething(user, password) So wherever I need these properties, I can do steps above. (2) I create a meaningful Class to represent these properties; say, ApplicationConfig and provide getters to get specific properties. So above code may look like: ApplicationConfig config = ApplicationConfig.getInstance(); doSomething(config.getSecretUserId(), config.getPassword()); //ApplicationConfig would have instance variables that are initialized during // getInstance() after loading from properties file. Note: The properties file as such will have only minor changes in the future. My personal choice is (2) - let me hear some comments?

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  • Modelling Business Logic with NON-Techies

    - by cbmeeks
    The setup: Winform/ASP.NET MVC projects. Learning NHibernate SQL-Server driven apps I work with clients that have no idea how to model an application. That's what I'm for. However, we have lots of conflicts with validation, mis-understandings, etc. For example, the client will ask for an order entry screen. The screen should require a "product". That's fine and dandy. However, the client didn't know to tell me that the user can't order a product of "Class A" unless it's Tuesday. Or, they need a time entry screen. 2 days before it's rolled into production, they casually forgot to mention that certain activities are only valid for certain situations. These situations being a week of coding. That's of course, some crude examples (not by much!). But the problem is getting these non-technical clients to layout their business logic. They somehow didn't realize that the "Class A" problem would come up two weeks later, etc. I'm all for agile programming but is there an easy way to somehow make business logic like this extremely easy to implement and change on almost a daily basis? I of course am splitting the project into hopefully intelligent pieces, using NHibernate, etc. But making this BI logic so dynamic is really making it hard to project timelines, etc. Any suggestions? I know there will never be a perfect client (or a perfect provider) but how do you guys deal with the constant mis-understandings? Thanks.

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  • Running SQLite 3 in MicroApache

    - by Alien426
    I'm running MicroApache (http://microapache.amadis.sytes.net) on Windows XP and would like to use SQLite 3 databases. The PHP version is 5.2.9-2. My MicroApache version has SQLite 2 support through 2 lines in the php.ini: extension=php_pdo.dll extension=php_sqlite.dll I test whether the extension works in 3 ways: 1. phpinfo() 2. extension_loaded() and get_loaded_extensions() 3. using sample code that var_dump()s the constant SQLITE3_NUM (should be the integer 2) and tries to create a database (error: class 'SQLite3' does not exist) Things I have tried (if I can remember them all): 1. copied php_sqlite3.dll from a full installation of PHP and added "extension=php_sqlite3.dll" to php.ini - error "Procedure entry point gc_remove_zval_from_buffer was not found in php5ts.dll" 2. compressed the DLL with UPX (like the other DLLs of MicroApache seem to be) - does not display an error on start, nor in the log file, but does not work 3. tried various things with php.ini - created a section "[sqlite3]" - prefixed "sqlite3." to "extension_dir=." and "extension=php_sqlite3.dll" - ... 4. tried to use PDO, it says it 'could not find driver' Who can help me get SQLite 3 to work?

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  • Fixed div background

    - by Fahad
    I want to create a layout where I want to display an image to the left and content on the right. The image should stay constant when the content scrolls. The css I'm using: <style type="text/css"> html, body { margin:0; padding:0; } #page-container { margin:auto; width:900px; background-color:Black; background-image:url('images/desired_layout.png'); background-attachment: fixed; background-repeat:no-repeat; } #main-image { float:left; width:250px; height:687px; background-image:url('images/desired_layout.png'); background-attachment:fixed; background-repeat:no-repeat; } #content { margin-left:250px; background-color:Olive; height:800px; width:650px; } </style> The HTML: <div id="page-container"> <div id="main-image"></div> <div id="content"></div> </div> Alot of time on this site and I have understood that background-attachment:fixed positions the image in the entire viewport and not the element it is applied to. My question is how do I go about creating that kind of layout? I do not want to give that image as a background image, as if the window is resized, it might get hidden. I want scrollbars to appear if the window size is less than 900px( my page width) so that the image can be viewed at all times. That happens with this code, however I would like the image to start at my element instead. How do I go about doing this?? Thanks in Advance :)

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  • Is 1/0 a legal Java expression?

    - by polygenelubricants
    The following compiles fine in my Eclipse: final int j = 1/0; // compiles fine!!! // throws ArithmeticException: / by zero at run-time Java prevents many "dumb code" from even compiling in the first place (e.g. "Five" instanceof Number doesn't compile!), so the fact this didn't even generate as much as a warning was very surprising to me. The intrigue deepens when you consider the fact that constant expressions are allowed to be optimized at compile time: public class Div0 { public static void main(String[] args) { final int i = 2+3; final int j = 1/0; final int k = 9/2; } } Compiled in Eclipse, the above snippet generates the following bytecode (javap -c Div0) Compiled from "Div0.java" public class Div0 extends java.lang.Object{ public Div0(); Code: 0: aload_0 1: invokespecial #8; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: iconst_5 1: istore_1 // "i = 5;" 2: iconst_1 3: iconst_0 4: idiv 5: istore_2 // "j = 1/0;" 6: iconst_4 7: istore_3 // "k = 4;" 8: return } As you can see, the i and k assignments are optimized as compile-time constants, but the division by 0 (which must've been detectable at compile-time) is simply compiled as is. javac 1.6.0_17 behaves even more strangely, compiling silently but excising the assignments to i and k completely out of the bytecode (probably because it determined that they're not used anywhere) but leaving the 1/0 intact (since removing it would cause an entirely different program semantics). So the questions are: Is 1/0 actually a legal Java expression that should compile anytime anywhere? What does JLS say about it? If this is legal, is there a good reason for it? What good could this possibly serve?

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  • Creating/Maintaining a large project-agnostic code library

    - by bufferz
    In order to reduce repetition and streamline testing/debugging, I'm trying to find the best way to develop a group of libraries that many projects can utilize. I'd like to keep individual executable relatively small, and have shared libraries for math, database, collections, graphics, etc. that were previously scattered among several projects and in many cases duplicated (bad!). This library is to be in an SVN repo and several programmers will be working on it. This library will be in constant development along with the executables that utilize it. For example, I want a code file in ProjectA to look something like the following: using MyCompany.Math.2D; //static 2D math methods using MyCompany.Math.3D; //static #D math methods using MyCompany.Comms.SQL; //static methods for doing simple SQLDB I/O using MyCompany.Graphics.BitmapOperations; //static methods that play with bitmaps So in my ProjectA solution file in VisualStudio, in order to develop/debug the MyCompany library I have to add several projects (Math, Comms, Graphics). Things get pretty cluttered and Solution files get out of date quickly between programmer SVN commits. I'm just looking for a high level approach to maintaining a large, shared code base in an SCN repository. I am fully willing to radically redesign my approach. I'm looking for that warm fuzzy feeling you get when you're design approach is spot on and development is fluid and natural. And ideas? Thanks!!

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  • Rails performance tests "rake test:benchmark" and "rake test:profile" give me errors

    - by go minimal
    I'm trying to run a blank default performance test with Ruby 1.9 and Rails 2.3.5 and I just can't get it to work! What am I missing here??? rails testapp cd testapp script/generate scaffold User name:string rake db:migrate rake test:benchmark - /usr/local/bin/ruby19 -I"lib:test" "/usr/local/lib/ruby19/gems/1.9.1/gems/rake-0.8.7/lib/rake/rake_test_loader.rb" "test/performance/browsing_test.rb" -- --benchmark Loaded suite /usr/local/lib/ruby19/gems/1.9.1/gems/rake-0.8.7/lib/rake/rake_test_loader Started /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:105:in `rescue in const_missing': uninitialized constant BrowsingTest::STARTED (NameError) from /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:94:in `const_missing' from /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/testing/performance.rb:38:in `run' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:415:in `block (2 levels) in run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:409:in `each' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:409:in `block in run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:408:in `each' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:408:in `run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:388:in `run' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:329:in `block in autorun' rake aborted! Command failed with status (1): [/usr/local/bin/ruby19 -I"lib:test" "/usr/l...]

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  • Java - Custom PropertyEditorSupport to display units

    - by I82Much
    All, I'm trying to make the properties of my node have Units associated with the measure. ( I am using the JScience.org implementation of JSR 275) So for instance, public class Robot extends AbstractNode { // in kg float vehicleMass; @Override public Sheet createSheet() { Sheet s = Sheet.createDefault(); Sheet.Set set = s.createPropertiesSet(); try { PropertySupport.Reflection vehicleMassField = new PropertySupport.Reflection(this, float.class, "vehicleMass"); vehicleMassField.setValue("units", SI.KILOGRAMS); vehicleMassField.setName("vehicleMass"); set.put(vehicleMassField); PropertyEditorManager.registerEditor(float.class, UnitInPlaceEditor.class); } catch (NoSuchMethodException ex) { Exceptions.printStackTrace(ex); } s.put(set); return s; } } I want my UnitInPlaceEditor to append the units to the end of the string representation of the number, and when the field is clicked (enters edit mode) for the units to disappear and just the number becomes selected for editing. I can make the units appear, but I cannot get the units to disappear when the field enters editing mode. public class UnitsInplaceEditor extends PropertyEditorSupport implements ExPropertyEditor { private PropertyEnv pe; @Override public String getAsText() { // Append the unit by retrieving the stored value } @Override public void setAsText(String s) { // strip off the unit, parse out the number } public void attachEnv(PropertyEnv pe) { this.pe = pe; } } Here's a screenshot of the display - I like it like this.. but here's the value being edited; note the unit stays there. Basically I want one value (string) to be displayed in the field when the field is NOT being edited, and a different to be displayed when user starts editing the field. Barring that, I'd like to put a constant jlabel for the units (uneditable) to the right of the text field. Anyone know how to do this?

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  • Run AppleScript with Elevated Privileges from Objective C

    - by cygnl7
    I'm attempting to execute an uninstaller (written in AppleScript) through AuthorizationExecuteWithPrivileges. I'm setting up my rights after creating an empty auth ref like so: char *tool = "/usr/bin/osascript"; AuthorizationItem items = {kAuthorizationRightExecute, strlen(tool), tool, 0}; AuthorizationRights rights = {sizeof(items)/sizeof(AuthorizationItem), &items}; AuthorizationFlags flags = kAuthorizationFlagDefaults | kAuthorizationFlagExtendRights | kAuthorizationFlagPreAuthorize | kAuthorizationFlagInteractionAllowed; status = AuthorizationCopyRights(authorizationRef, &rights, NULL, flags, NULL); Later I call: status = AuthorizationExecuteWithPrivileges(authorizationRef, tool, kAuthorizationFlagDefaults, (char *const *)args, NULL); On Snow Leopard this works fine, but on Leopard I get the following in syslog.log: Apr 19 15:30:09 hostname /usr/bin/osascript[39226]: OpenScripting.framework - 'gdut' event blocked in process with mixed credentials (issetugid=0 uid=501 euid=0 gid=20 egid=20) Apr 19 15:30:12: --- last message repeated 1 time --- ... Apr 19 15:30:12 hostname [0x0-0x2e92e9].com.example.uninstaller[39219]: /var/folders/vm/vmkIi0nYG8mHMrllaXaTgk+++TI/-Tmp-/TestApp_tmpfiles/Uninstall.scpt: Apr 19 15:30:12 hostname [0x0-0x2e92e9].com.example.uninstaller[39219]: execution error: «constant afdmasup» doesn’t understand the «event earsffdr» message. (-1708) After researching this for a few hours my first guess is that Leopard somehow doesn't want to do what I'm doing because it knows it's in a setuid situation and blocks calls that ask about user-specific things in the applescript. Am I going about this all wrong? I just want to run the equivalent of "sudo /usr/bin/osascript ..." Edit: FWIW, the first line that causes the "execution error" is: set userAppSupportPath to (POSIX path of (path to application support folder from user domain)) However, even with an empty script (on run argv, end run and that's it) I still get the 'gdut' message.

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  • The algorithm used to generate recommendations in Google News?

    - by Siddhant
    Hi everyone. I'm study recommendation engines, and I went through the paper that defines how Google News generates recommendations to users for news items which might be of their interest, based on collaborative filtering. One interesting technique that they mention is Minhashing. I went through what it does, but I'm pretty sure that what I have is a fuzzy idea and there is a strong chance that I'm wrong. The following is what I could make out of it :- Collect a set of all news items. Define a hash function for a user. This hash function returns the index of the first item from the news items which this user viewed, in the list of all news items. Collect, say "n" number of such values, and represent a user with this list of values. Based on the similarity count between these lists, we can calculate the similarity between users as the number of common items. This reduces the number of comparisons a lot. Based on these similarity measures, group users into different clusters. This is just what I think it might be. In Step 2, instead of defining a constant hash function, it might be possible that we vary the hash function in a way that it returns the index of a different element. So one hash function could return the index of the first element from the user's list, another hash function could return the index of the second element from the user's list, and so on. So the nature of the hash function satisfying the minwise independent permutations condition, this does sound like a possible approach. Could anyone please confirm if what I think is correct? Or the minhashing portion of Google News Recommendations, functions in some other way? I'm new to internal implementations of recommendations. Any help is appreciated a lot. Thanks!

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  • Generate a set of strings with maximum edit distance

    - by Kevin Jacobs
    Problem 1: I'd like to generate a set of n strings of fixed length m from alphabet s such that the minimum Levenshtein distance (edit distance) between any two strings is greater than some constant c. Obviously, I can use randomization methods (e.g., a genetic algorithm), but was hoping that this may be a well-studied problem in computer science or mathematics with some informative literature and an efficient algorithm or three. Problem 2: Same as above except that adjacent characters cannot repeat; the i'th character in each string may not be equal to the i+1'th character. E.g., 'CAT', 'AGA' and 'TAG' are allowed, 'GAA', 'AAT', and 'AAA' are not. Background: The basis for this problem is bioinformatic and involves designing unique DNA tags that can be attached to biologically derived DNA fragments and then sequenced using a fancy second generation sequencer. The goal is to be able to recognize each tag, allowing for random insertion, deletion, and substitution errors. The specific DNA sequencing technology has a relatively low error rate per base (~1%), but is less precise when a single base is repeated 2 or more times (motivating the additional constraints imposed in problem 2).

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  • Why is there unreachable code here?

    - by Richard
    I am writing a c# app and want to output error messages to either the console or a messagebox (Depending on the app type: enum AppTypeChoice { Console, Windows } ), and also control wether the app keeps running or not ( bool StopOnError ). I came up with this method that will check all the criteria, but I'm getting an "unreachable code detected" warning. I can't see why! Here is the whole method (Brace yourselves for some hobbyist code!) public void OutputError(string message) { string standardMessage = "Something went WRONG!. [ But I'm not telling you what! ]"; string defaultMsgBoxTitle = "Aaaaarrrggggggggggg!!!!!"; string dosBoxOutput = "\n\n*** " + defaultMsgBoxTitle + " *** \n\n Message was: '" + message + "'\n\n"; AppTypeChoice appType = DataDefs.AppType; DebugLevelChoice level = DataDefs.DebugLevel; // Decide how much info we should give out here... if (level != DebugLevelChoice.None) { // Give some info.... if (appType == AppTypeChoice.Windows) MessageBox.Show(message, defaultMsgBoxTitle, MessageBoxButtons.OK, MessageBoxIcon.Error); else Console.WriteLine(dosBoxOutput); } else { // Be very secretive... if (appType == AppTypeChoice.Windows) MessageBox.Show(standardMessage, defaultMsgBoxTitle, MessageBoxButtons.OK, MessageBoxIcon.Error); else Console.WriteLine(standardMessage); } // Decide if app falls over or not.. if (DataDefs.StopOnError == true) Environment.Exit(0); // UNREACHABLE CODE HERE } Also, while I have your attention, to get the app type, I'm just using a constant at the top of the file (ie. AppTypeChoice.Console in a Console app etc) - is there a better way of doing this (i mean finding out in code if it is a DOS or Windows app)? Also, I noticed that I can use a messagebox with a fully-qualified path in a Console app...How bad is is to do that ( I mean, will I get tarred and feathered when other developers see it?!) Thanks for your help

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  • boost::lambda bind expressions can't get bind to string's empty() to work

    - by navigator
    Hi, I am trying to get the below code snippet to compile. But it fails with: error C2665: 'boost::lambda::function_adaptor::apply' : none of the 8 overloads could convert all the argument types. Sepcifying the return type when calling bind does not help. Any idea what I am doing wrong? Thanks. #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <string> #include <map> int main() { namespace bl = boost::lambda; typedef std::map<int, std::string> types; types keys_and_values; keys_and_values[ 0 ] = "zero"; keys_and_values[ 1 ] = "one"; keys_and_values[ 2 ] = "Two"; std::for_each( keys_and_values.begin(), keys_and_values.end(), std::cout << bl::constant("Value empty?: ") << std::boolalpha << bl::bind(&std::string::empty, bl::bind(&types::value_type::second, _1)) << "\n"); return 0; }

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  • Calculating bounding box a certain distance away from a lat/long coordinate in Java

    - by Bryce Thomas
    Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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  • How can I work around the fact that in C++, sin(M_PI) is not 0?

    - by Adam Doyle
    In C++, const double Pi = 3.14159265; cout << sin(Pi); // displays: 3.58979e-009 it SHOULD display the number zero I understand this is because Pi is being approximated, but is there any way I can have a value of Pi hardcoded into my program that will return 0 for sin(Pi)? (a different constant maybe?) In case you're wondering what I'm trying to do: I'm converting polar to rectangular, and while there are some printf() tricks I can do to print it as "0.00", it still doesn't consistently return decent values (in some cases I get "-0.00") The lines that require sin and cosine are: x = r*sin(theta); y = r*cos(theta); BTW: My Rectangular - Polar is working fine... it's just the Polar - Rectangular Thanks! edit: I'm looking for a workaround so that I can print sin(some multiple of Pi) as a nice round number to the console (ideally without a thousand if-statements) edit: In case anyone's curious, this was what I landed on: double sin2(double theta) // in degrees { double s = sin(toRadians(theta)); if (fabs(s - (int)s) < 0.000001) { return floor(s + 0.5); } return s; } where toRadians() is a macro that converts to radians

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  • Raw types and subtyping

    - by Dmitrii
    We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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  • How to provide js-ctypes in a spidermonkey embedding?

    - by Triston J. Taylor
    Summary I have looked over the code the SpiderMonkey 'shell' application uses to create the ctypes JavaScript object, but I'm a less-than novice C programmer. Due to the varying levels of insanity emitted by modern build systems, I can't seem to track down the code or command that actually links a program with the desired functionality. method.madness This js-ctypes implementation by The Mozilla Devs is an awesome addition. Since its conception, scripting has been primarily used to exert control over more rigorous and robust applications. The advent of js-ctypes to the SpiderMonkey project, enables JavaScript to stand up and be counted as a full fledged object oriented rapid application development language flying high above 'the bar' set by various venerable application development languages such as Microsoft's VB6. Shall we begin? I built SpiderMonkey with this config: ./configure --enable-ctypes --with-system-nspr followed by successful execution of: make && make install The js shell works fine and a global ctypes javascript object was verified operational in that shell. Working with code taken from the first source listing at How to embed the JavaScript Engine -MDN, I made an attempt to instantiate the JavaScript ctypes object by inserting the following code at line 66: /* Populate the global object with the ctypes object. */ if (!JS_InitCTypesClass(cx, global)) return NULL; /* I compiled with: g++ $(./js-config --cflags --libs) hello.cpp -o hello It compiles with a few warnings: hello.cpp: In function ‘int main(int, const char**)’: hello.cpp:69:16: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] hello.cpp:80:20: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] hello.cpp:89:17: warning: NULL used in arithmetic [-Wpointer-arith] But when you run the application: ./hello: symbol lookup error: ./hello: undefined symbol: JS_InitCTypesClass Moreover JS_InitCTypesClass is declared extern in 'dist/include/jsapi.h', but the function resides in 'ctypes/CTypes.cpp' which includes its own header 'CTypes.h' and is compiled at some point by some command during 'make' to yeild './CTypes.o'. As I stated earlier, I am less than a novice with the C code, and I really have no idea what to do here. Please give or give direction to a generic example of making the js-ctypes object functional in an embedding.

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  • PHP CodeIgniter Framework - Thoughts on developing with it?

    - by Sootah
    I've been reviewing different frameworks to use for my next couple of major web applications, and after days of research am almost set on using CodeIgniter. The reason I'm leaning towards CI is that so far it looks to be the best suited for me. It doesn't require constant command-line access (I am currently using shared hosting; the projects do not warrant a dedicate server yet), nothing special has to be installed on the server running it (you just upload the framework to the root of whatever your developing), and they appear to have some excellent documentation, videos, and tutorials on how to get started. Do any of you have experience with CodeIgniter? If so, what is your opinion of it and its features? What had you developed with it, and what types of applications is it best suited to create? I certainly don't want to get into a situation where I'm trying to bend a framework to do something that it isn't well-suited for. Both of my projects will be database-driven apps that will require user registration, the ability to manipulate data that is specific to their account (their posts, listings, user account details, etc), amongst other things. Also, if you have any other PHP framework suggestions, I am open to them. Thanks in advance for your help! -Sootah

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  • Theory: "Lexical Encoding"

    - by _ande_turner_
    I am using the term "Lexical Encoding" for my lack of a better one. A Word is arguably the fundamental unit of communication as opposed to a Letter. Unicode tries to assign a numeric value to each Letter of all known Alphabets. What is a Letter to one language, is a Glyph to another. Unicode 5.1 assigns more than 100,000 values to these Glyphs currently. Out of the approximately 180,000 Words being used in Modern English, it is said that with a vocabulary of about 2,000 Words, you should be able to converse in general terms. A "Lexical Encoding" would encode each Word not each Letter, and encapsulate them within a Sentence. // An simplified example of a "Lexical Encoding" String sentence = "How are you today?"; int[] sentence = { 93, 22, 14, 330, QUERY }; In this example each Token in the String was encoded as an Integer. The Encoding Scheme here simply assigned an int value based on generalised statistical ranking of word usage, and assigned a constant to the question mark. Ultimately, a Word has both a Spelling & Meaning though. Any "Lexical Encoding" would preserve the meaning and intent of the Sentence as a whole, and not be language specific. An English sentence would be encoded into "...language-neutral atomic elements of meaning ..." which could then be reconstituted into any language with a structured Syntactic Form and Grammatical Structure. What are other examples of "Lexical Encoding" techniques? If you were interested in where the word-usage statistics come from : http://www.wordcount.org

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  • Testing Finite State Machines

    - by Pondidum
    I have inherited a large and firaly complex state machine at work. It has 31 possbile states to be in. It has the following inputs: Enum: Current State (so 0 - 30) Enum: source (currently only 2 entries) Boolean: Request Boolean: type Enum: Status (3 states) Enum: Handling (3 states) Boolean: Completed The 31 States are really needed (big business process). Breaking into seperate state machines doesnt seem feasable - each state is distinct. I have written tests for one set of inputs (the most common set), with one test per input (all inputs constant, except for the State input): [Subject("Application Process States")] public class When_state_is_meeting2Requested : AppProcessBase { Establish context = () => { //Setup.... }; Because of = () => process.Load(jas, vac); It Current_node_should_be_meeting2Requested = () => process.CurrentNode.ShouldBeOfType<meetingRequestedNode>(); It Can_move_to_clientDeclined = () => Check(process, process.clientDeclined); It Can_move_to_meeting1Arranged = () => Check(process, process.meeting1Arranged); It Can_move_to_meeting2Arranged = () => Check(process, process.meeting2Arranged); It Can_move_to_Reject = () => Check(process, process.Reject); It Cannot_move_to_any_other_state = () => AllOthersFalse(process); } As no one is entirely sure on what the output should be for each state and set of inputs i have been starting to write tests for it, however on calculation i will need to write 4320 ( 30*2*2*2*3*3*2 ) tests for it. Does anyone have any suggestions on how i should go about testing this?

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  • Generating Random Records Date Wise

    - by Julian
    I work for a non-profit organization where we send volunteers to aided schools everyday. I am creating a site to display this info and am using SQL server express. I want some help regarding a query so here's my first post We have 15 volunteers currently who will go to 4 different schools to teach. Here are some conditions: We have to create a 'new' group comprising of 1 Leader and 4 TeamSupporters 'every day' except Sunday who will go to teach everyday If a person becomes a Leader in a week, he cannot become a leader again for the same week. A leader can become a TeamSupporter in the same week. Moving ahead, we can have more number of school to target, so 4 is not a constant Here's how the output should look like School1 School2 School3 School4 Jun14 Leader V6 V6 V6 V6 Support1 V3 V3 V3 V3 Support2 V9 V9 V9 V9 Support3 V12 V12 V12 V12 Support4 V1 V1 V1 V1 Jun15 Leader V2 V2 V2 V2 Support1 V7 V7 V7 V7 Support2 V9 V9 V9 V9 Support3 V8 V8 V8 V8 Support4 V11 V11 V11 V11 Jun16 Leader V9 V9 V9 V9 Support1 V6 V6 V6 V6 Support2 V4 V4 V4 V4 Support3 V3 V3 V3 V3 Support4 V14 V14 V14 V14 and so on..

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