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• Web Services Primer for a WinForms Developer?

  - by Unicorns

  I've been writing client/server applications with Winforms for about six years now, but I have yet to venture into the web space (neither ASP.NET nor web services). Given the direction that the job market has been heading for some time and the fact that I have a basic curiosity, I'd like to get involved with writing web services, but I don't know where to start. I've read about various options (XML/SOAP vs. JSON, REST vs...well, actually I don't know what it's called, etc.), but I'm not sure what sort of criteria are in play when making the determination to use one or the other. Obviously, I'd like to leverage the tools that I have (Visual Studio, the .NET framework, etc.) without hamstringing myself into only targeting a particular audience (i.e. writing the service in such a way as to make it difficult to consume from a Windows Mobile/Android/iPhone client, for example). For the record, my plan--for now--is to use WCF for my web service development, but I'm open to using another .NET approach if that's advisable. I realize that this question is pretty open-ended so it may get closed, but here are some things I'm wondering: What are some things to consider when choosing the type of web service (REST, etc.) I intend to write? Is it possible (and, if so, feasible) to move from one approach to another? Can web services be written in an event-driven way? As I said I'm a Winforms developer, so I'm used to objects raising events for me to react to. For instance, if I have two clients connected to my service, is there a way for me to "push" information to one of them as a result of an action by the other? If this is possible, is this advisable or am I just not thinking about it correctly? What authentication mechanisms seem to work best for public-facing services? What about if I plan to have different types of OS'es and clients connecting to the service? Is there a generally accepted platform-agnostic approach? In the line of authentication, is this something that I should be doing myself (authenticating an managing sessions, etc.) or is this something should be handled at the framework level and I just define exactly how it should work? If that's the case, how do I tell who the requester has authenticated themselves as? I started writing an authentication mechanism (simple username/password combinations stored in the database and a corresponding session table with a GUID key) within my service and just requiring that key to be passed with every operation (other than logging in, of course), but I want to make sure that I'm not reinventing the wheel here. However, I also don't want to clutter up the server with a bunch of machine user accounts just to use Basic authentication. I'm also under the impression that Digest (and of course Windows) authentication requires a machine (or AD) user account.

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• MATLAB: different function returns from command line and within function

  - by Myx

  Hello: I have an extremely bizzare situation: I have a function in MATLAB which calls three other main functions and produces two figures for me. The function reads in an input jpeg image, crops it, segments it using kmeans clustering, and outputs 2 figures to the screen - the original image and the clustered image with the cluster centers indicated. Here is the function in MATLAB: function [textured_avg_x photo_avg_x] = process_database_images() clear all warning off %#ok type_num_max = 3; % type is 1='texture', 2='graph', or 3='photo' type_num_max = 1; img_max_num_photo = 100; % 400 photo images img_max_num_other = 100; % 100 textured, and graph images for type_num = 1:2:type_num_max if(type_num == 3) img_num_max = img_max_num_photo; else img_num_max = img_max_num_other; end img_num_max = 1; for img_num = 1:img_num_max [type img] = load_image(type_num, img_num); %img = imread('..\images\445.jpg'); img = crop_image(img); [IDX k block_bounds features] = segment_image(img); end end end The function segment_image first shows me the color image that was passed in, performs kmeans clustering, and outputs the clustered image. When I run this function on a particular image, I get 3 clusters (which is not what I expect to get). When I run the following commands from the MATLAB command prompt: >> img = imread('..\images\texture\1.jpg'); >> img = crop_image(img); >> segment_image(img); then the first image that is displayed by segment_image is the same as when I run the function (so I know that the clustering is done on the same image) but the number of clusters is 16 (which is what I expect). In fact, when I run my process_database_images() function on my entire image database, EVERY image is evaluated to have 3 clusters (this is a problem), whereas when I test some images individually, I get in the range of 12-16 clusters, which is what I prefer and expect. Why is there such a discrepancy? Am I having some syntax bug in my process_database_images() function? If more code is required from me (i.e. segment_images function, or crop_image function), please let me know. Thanks.

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• JavaCC: How can one exclude a string from a token? (A.k.a. understanding token ambiguity.)

  - by java.is.for.desktop

  Hello, everyone! I had already many problems with understanding, how ambiguous tokens can be handled elegantly (or somehow at all) in JavaCC. Let's take this example: I want to parse XML processing instruction. The format is: "<?" <target> <data> "?>": target is an XML name, data can be anything except ?>, because it's the closing tag. So, lets define this in JavaCC: (I use lexical states, in this case DEFAULT and PROC_INST) TOKEN : <#NAME : (very-long-definition-from-xml-1.1-goes-here) > TOKEN : <WSS : (" " | "\t")+ > // WSS = whitespaces <DEFAULT> TOKEN : {<PI_START : "<?" > : PROC_INST} <PROC_INST> TOKEN : {<PI_TARGET : <NAME> >} <PROC_INST> TOKEN : {<PI_DATA : ~[] >} // accept everything <PROC_INST> TOKEN : {<PI_END : "?>" > : DEFAULT} Now the part which recognizes processing instructions: void PROC_INSTR() : {} { ( <PI_START> (t=<PI_TARGET>){System.out.println("target: " + t.image);} <WSS> (t=<PI_DATA>){System.out.println("data: " + t.image);} <PI_END> ) {} } Let's test it with <?mytarget here-goes-some-data?>: The target is recognized: "target: mytarget". But now I get my favorite JavaCC parsing error: !! procinstparser.ParseException: Encountered "" at line 1, column 15. !! Was expecting one of: !! Encountered nothing? Was expecting nothing? Or what? Thank you, JavaCC! I know, that I could use the MORE keyword of JavaCC, but this would give me the whole processing instruction as one token, so I'd had to parse/tokenize it further by myself. Why should I do that? Am I writing a parser that does not parse? The problem is (i guess): hence <PI_DATA> recognizes "everything", my definition is wrong. I should tell JavaCC to recognize "everything except ?>" as processing instruction data. But how can it be done? NOTE: I can only exclude single characters using ~["a"|"b"|"c"], I can't exclude strings such as ~["abc"] or ~["?>"]. Another great anti-feature of JavaCC. Thank you.

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• generated service mock: everything but RhinoMocks fails?

  - by hko

  I have the "quest" to search for the next Mocking Framework for my company, and basically it's down to NSubstitute (simplest syntax, but no strict mocks), FakeItEasy(best reviews, Roy Osherove bonus, and slightly better lib support than NSubstitute), Moq (best "other libs support", biggest featureset, downside: mock.Object). We definitely want to move on from RhinoMocks, e.g. because of the unusefull interactiontest error messages (it should tell me what the parameter was instead, when a verification fails). So I was pretty surprised the other day (that was yesterday) when I found out RhinoMocks could do a thing where every other mock framework fails at: Mocking an autogenerated SomethingService (a typical VS autogenerated service with a default construtor in a partial class). Please don't argue about the design.. I intend to write lightweight integration tests (and some unit tests), and I can't mess around with the service, the product is installed on too many customers system. See this code: // here the NSubstitute and FakeItEasy equivalents throw an exception.. see below TicketStoreService fakeTicketStoreService = MockRepository.GenerateMock<TicketStoreService>(); fakeTicketStoreService.Expect(service => service.DoSomething(Arg.Is(new Guid())).Return(new Guid()); fakeTicketStoreService.DoSomething(Arg.Is(new Guid())); fakeTicketStoreService.VerifyAllExpectations(); Note that DoSomething is a non-virtual methodcall in an autogenerated class. So it shouldn't work, according to common knowledge. But it does. Problem is that it's the only (non commercial) framework that can do this: Rhino.Mocks works, and verification works too FakeItEasy says it doesn't find a default constructor (probably just wrong exception message): No default constructor was found on the type SomeNamespace.TicketStoreService Moq gives something sane and understandable: Invalid setup on a non-virtual (overridable in VB) member: service=> service.DoSomething Nsubstitute gives a message System.NotSupportedException: Cannot serialize member System.ComponentModel.Component.Site of type System.ComponentModel.ISite because it is an interface. I'm really wondering what's going on here with the frameworks, except Moq. The "fancy new" frameworks seem to have an initial perf hit too, probably preparing some Type cache and serializing stuff, whilst RhinoMocks somehow manages to create a very "slim" mock without recursion. I have to admit I didn't like RhinoMocks very well, but here it shines.. unfortunately. So, is there a way to get that to work with newer (non-commercial!) mocking frameworks, or somehow get a sane error message out of Rhino.Mocks? And why can Rhino.Mocks achieve this, when clearly every Mocking framework states it can only work with virtual methods when given a concrete class? Let's not derail the discussion by talking about alternative approaches like Extract&Override or runtime-proxy Mocking frameworks like JustMock/TypeMock/Moles or the new Fakes framework, I know these, but that would be less ideal solutions, for reasons beyond this topic. Any help appreciated..

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• How to use constraint programming for optimizing shopping baskets?

  - by tangens

  I have a list of items I want to buy. The items are offered by different shops and different prices. The shops have individual delivery costs. I'm looking for an optimal shopping strategy (and a java library supporting it) to purchase all of the items with a minimal total price. Example: Item1 is offered at Shop1 for $100, at Shop2 for $111. Item2 is offered at Shop1 for $90, at Shop2 for $85. Delivery cost of Shop1: $10 if total order < $150; $0 otherwise Delivery cost of Shop2: $5 if total order < $50; $0 otherwise If I buy Item1 and Item2 at Shop1 the total cost is $100 + $90 +$0 = $190. If I buy Item1 and Item2 at Shop2 the total cost is $111 + $85 +$0 = $196. If I buy Item1 at Shop1 and Item2 at Shop2 the total cost is $100 + $10 + $85 + $0 = 195. I get the minimal price if I order Item1 and Item2 at Shop1: $190 What I tried so far I asked another question before that led me to the field of constraint programming. I had a look at cream and choco, but I did not figure out how to create a model to solve my problem. | shop1 | shop2 | shop3 | ... ----------------------------------------- item1 | p11 | p12 | p13 | item2 | p21 | p22 | p23 | . | | | | . | | | | ----------------------------------------- shipping | s1 | s2 | s3 | limit | l1 | l2 | l3 | ----------------------------------------- total | t1 | t2 | t3 | ----------------------------------------- My idea was to define these constraints: each price "p xy" is defined in the domain (0, c) where c is the price of the item in this shop only one price in a line should be non zero if one or more items are bought from one shop and the sum of the prices is lower than limit, then add shipping cost to the total cost shop total cost is the sum of the prices of all items in a shop total cost is the sum of all shop totals The objective is "total cost". I want to minimize this. In cream I wasn't able to express the "if then" constraint for conditional shipping costs. In choco these constraints exist, but even for 5 items and 10 shops the program was running for 10 minutes without finding a solution. Question How should I express my constraints to make this problem solvable for a constraint programming solver?

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• How to troubleshoot a Highcharts script that's not rendering data when date is added and hanging the JS engine with large datasets?

  - by ylluminate

  I have a Highchart JS graph that I'm building in Rails (although I don't think Ruby has real bearing on this problem unless it's the Date output format) to which I'm adding the timestamp of each datapoint. Presently the array of floats is rendering fine without timestamps, however when I add the timestamp to the series it fails to rend. What's worse is that when the series has hundreds of entries all sorts of problems arise, not the least of which is the browser entirely hanging and requiring a force quit / kill. I'm using the following to build the array of arrays data series: series1 = readings.map{|row| [(row.date.to_i * 1000), (row.data1.to_f if BigDecimal(row.data1) != BigDecimal("-1000.0"))] } This yields a result like this: series: [{"name":"Data 1","data":[[1326262980000,1.79e-09],[1326262920000,1.29e-09],[1326262860000,1.22e-09],[1326262800000,1.42e-09],[1326262740000,1.29e-09],[1326262680000,1.34e-09],[1326262620000,1.31e-09],[1326262560000,1.51e-09],[1326262500000,1.24e-09],[1326262440000,1.7e-09],[1326262380000,1.24e-09],[1326262320000,1.29e-09],[1326262260000,1.53e-09],[1326262200000,1.23e-09],[1326262140000,1.21e-09]],"color":"blue"}] Yet nothing appears on the graph as noted. Notwithstanding, when I compare the data series in one of their very similar examples here: http://www.highcharts.com/demo/spline-irregular-time It appears that really the data series are formatted identically (except in mine I use the timestamp vs date method). This leads me to think I've got a problem with the timestamp output, but I'm just not able to figure out where / how as I'm converting the date output to an integer multipled by 1000 to convert it to milliseconds as per explained in a similar Railscasts tutorial. I would very much appreciate it if someone could point me in the right direction here as to what I may be doing wrong. What could cause no data to appear on the graph in smaller sized sets (<100 points) and when into the hundreds causes an apparent hang in the javascript engine in this case? Perhaps ultimately the key lies here as this is the entire js that's being generated and not rendering: jQuery(function() { // 1. Define JSON options var options = { chart: {"defaultSeriesType":"spline","renderTo":"chart_name"}, title: {"text":"Title"}, legend: {"layout":"vertical","style":{}}, xAxis: {"title":{"text":"UTC Time"},"type":"datetime"}, yAxis: [{"title":{"text":"Left Title","margin":10}},{"title":{"text":"Right Groups Title"},"opposite":true}], tooltip: {"enabled":true}, credits: {"enabled":false}, plotOptions: {"areaspline":{}}, series: [{"name":"Data 1","data":[[1326262980000,1.79e-08],[1326262920000,1.69e-08],[1326262860000,1.62e-08],[1326262800000,1.42e-08],[1326262740000,1.29e-08],[1326262680000,1.34e-08],[1326262620000,1.31e-08],[1326262560000,1.51e-08],[1326262500000,1.64e-08],[1326262440000,1.7e-08],[1326262380000,1.64e-08],[1326262320000,1.69e-08],[1326262260000,1.53e-08],[1326262200000,1.23e-08],[1326262140000,1.21e-08]],"color":"blue"},{"name":"Data 2","data":[[1326262980000,9.79e-09],[1326262920000,9.78e-09],[1326262860000,9.8e-09],[1326262800000,9.82e-09],[1326262740000,9.88e-09],[1326262680000,9.89e-09],[1326262620000,1.3e-06],[1326262560000,1.32e-06],[1326262500000,1.33e-06],[1326262440000,1.33e-06],[1326262380000,1.34e-06],[1326262320000,1.33e-06],[1326262260000,1.32e-06],[1326262200000,1.32e-06],[1326262140000,1.32e-06]],"color":"red"}], subtitle: {} }; // 2. Add callbacks (non-JSON compliant) // 3. Build the chart var chart = new Highcharts.StockChart(options); });

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• php MySQL snytax error

  - by Jacksta

  my scrip is supposed to look up contacts in a table and present thm on the screen to then be edited. however this is not this case. I am getting the error Parse error: syntax error, unexpected $end in /home/admin/domains/domain.com.au/public_html/pick_modcontact.php on line 50 NOTE: this is the last line in this script. <? session_start(); if ($_SESSION[valid] != "yes") { header( "Location: contact_menu.php"); exit; } $db_name = "testDB"; $table_name = "my_contacts"; $connection = @mysql_connect("localhost", "user", "pass") or die(mysql_error()); $db = @mysql_select_db($db_name, $connection) or die(mysql_error()); $sql = "SELECT id, f_name, l_name FROM $table_name ORDER BY f_name"; $result = @mysql_query($sql, $connection) or die(mysql_error()); $num = @mysql_num_rows($result); if ($num < 1) { $display_block = "<p><em>Sorry No Results!</em></p>"; } else { while ($row = mysql_fetch_array($result)) { $id = $row['id']; $f_name = $row['f_name']; $l_name = $row['l_name']; $option_block .= "<option value\"$id\">$l_name, $f_name</option>"; } $display_block = "<form method=\"POST\" action=\"show_modcontact.php\"> <p><strong>Contact:</strong> <select name=\"id\">$option_block</select> <input type=\"submit\" name=\"submit\" value=\"Select This Contact\"></p> </form>"; ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Modify A Contact</title> </head> <body> <h1>My Contact Management System</h1> <h2><em>Modify a Contact</em></h2> <p>Select a contact from the list below, to modify the contact's record.</p> <? echo "$display_block"; ?> <br> <p><a href="contact_menu.php">Return to Main Menu</a></p> </body> </html>

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• How the simples GUI countdown is supposed to work?

  - by Roman

  I am trying to write the simples GUI countdown. I found in Internet some code but it is already too fancy for me. I am trying to keep it as simple as possible. So, I just want to have a window saying "You have 10 second left". The number of second should decrease every second from 10 to 0. I wrote a code. And I think I am close to the working solution. But I still missing something. Could you pleas help me to find out what is wrong? Here is my code: import javax.swing.*; public class Countdown { static JLabel label; // Method which defines the appearance of the window. private static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JLabel label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater(new Runnable(i,label) { public Runnable(int i, JLabel label) { this.i = i; this.label = label; } public void run() { label.setText("You have " + i + " seconds."); } }); } // The main method (entry point). public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); //counter.start(); } }); //counter.start(); } } And I have several concrete question about this code: Where should I place the counter.start();? (In my code I put it on 2 places. Which one is correct?) Why compiler complains about the constructor for Runnable? It says that I have an invalid method declaration and I need to specify the returned type. ADDED: I made the suggested corrections. And then I execute the code and get: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at Worker.run(Worker.java:12) In the Worker.java in the line 12 I have: label.setText("You have " + i + " seconds.");.

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• How to pass parameters to Apache Pivot's wtkx:include tag?

  - by Andrew Swan

  I need to create a reusable UI component that accepts a number of parameters (e.g. an image URL and some label text), similar to how JSP tags can accept parameters. The Pivot docs for the "wtkx:include" tag say: The tag allows a WTKX file to embed content defined in an external WTKX file as if it was defined in the source file itself. This is useful for ... defining reusable content templates I was hoping that I could define my component in a WTKX file using standard Pivot components (e.g. a TextInput) and pass it one or more parameters; for example my reusable template called "row.wtkx" might contain a row with an image and a text field, like this (where the ${xxx} bits are the parameters): <TablePane.Row xmlns="org.apache.pivot.wtk"> <ImageView image="@images/${image_url}" /> <TextInput text="${title}" /> </TablePane.Row> I could then reuse this component within a TablePane as follows: <rows> <TablePane.Row> <Label text="Painting"/> <Label text="Title"/> </TablePane.Row> <wtkx:include src="row.wtkx" image_url="mona_lisa.jpg" title="Mona Lisa"/> <wtkx:include src="row.wtkx" image_url="pearl_earring.jpg" title="Girl with a Pearl Earring"/> <wtkx:include src="row.wtkx" image_url="melting_clocks.jpg" title="Melting Clocks"/> </rows> I've made up the ${...} syntax myself just to show what I'm trying to do. Also, there could be other ways to pass the parameter values other than using attributes of the "wtkx:include" tag itself, e.g. pass a JSON-style map called say "args". The ability to pass parameters like this would make the include tag much more powerful, e.g. in my case allow me to eliminate a lot of duplication between the table row declarations. Or is "wtkx:include" not the right way to be doing this?

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• EF4: ObjectContext inconsistent when inserting into a view with triggers

  - by user613567

  I get an Invalid Operation Exception when inserting records in a View that uses “Instead of” triggers in SQL Server with ADO.NET Entity Framework 4. The error message says: {"The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: The key-value pairs that define an EntityKey cannot be null or empty. Parameter name: record"} @ at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options) at System.Data.Objects.ObjectContext.SaveChanges() In this simplified example I created two tables, Contacts and Employers, and one view Contacts_x_Employers which allows me to insert or retrieve rows into/from these two tables at once. The Tables only have a Name and an ID attributes and the view is based on a join of both: CREATE VIEW [dbo].[Contacts_x_Employers] AS SELECT dbo.Contacts.ContactName, dbo.Employers.EmployerName FROM dbo.Contacts INNER JOIN dbo.Employers ON dbo.Contacts.EmployerID = dbo.Employers.EmployerID And has this trigger: Create TRIGGER C_x_E_Inserts ON Contacts_x_Employers INSTEAD of INSERT AS BEGIN SET NOCOUNT ON; insert into Employers (EmployerName) select i.EmployerName from inserted i where not i.EmployerName in (select EmployerName from Employers) insert into Contacts (ContactName, EmployerID) select i.ContactName, e.EmployerID from inserted i inner join employers e on i.EmployerName = e.EmployerName; END GO The .NET Code follows: using (var Context = new TriggersTestEntities()) { Contacts_x_Employers CE1 = new Contacts_x_Employers(); CE1.ContactName = "J"; CE1.EmployerName = "T"; Contacts_x_Employers CE2 = new Contacts_x_Employers(); CE1.ContactName = "W"; CE1.EmployerName = "C"; Context.Contacts_x_Employers.AddObject(CE1); Context.Contacts_x_Employers.AddObject(CE2); Context.SaveChanges(); //? line with error } SSDL and CSDL (the view nodes): <EntityType Name="Contacts_x_Employers"> <Key> <PropertyRef Name="ContactName" /> <PropertyRef Name="EmployerName" /> </Key> <Property Name="ContactName" Type="varchar" Nullable="false" MaxLength="50" /> <Property Name="EmployerName" Type="varchar" Nullable="false" MaxLength="50" /> </EntityType> <EntityType Name="Contacts_x_Employers"> <Key> <PropertyRef Name="ContactName" /> <PropertyRef Name="EmployerName" /> </Key> <Property Name="ContactName" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> <Property Name="EmployerName" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> </EntityType> The Visual Studio solution and the SQL Scripts to re-create the whole application can be found in the TestViewTrggers.zip at ftp://JulioSantos.com/files/TriggerBug/. I appreciate any assistance that can be provided. I already spent days working on this problem.

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• Turning temporary stringstream to c_str() in single statement

  - by AshleysBrain

  Consider the following function: void f(const char* str); Suppose I want to generate a string using stringstream and pass it to this function. If I want to do it in one statement, I might try: f((std::ostringstream() << "Value: " << 5).str().c_str()); // error This gives an error: 'str()' is not a member of 'basic_ostream'. OK, so operator<< is returning ostream instead of ostringstream - how about casting it back to an ostringstream? 1) Is this cast safe? f(static_cast<std::ostringstream&>(std::ostringstream() << "Value: " << 5).str().c_str()); // incorrect output Now with this, it turns out for the operator<<("Value: ") call, it's actually calling ostream's operator<<(void*) and printing a hex address. This is wrong, I want the text. 2) Why does operator<< on the temporary std::ostringstream() call the ostream operator? Surely the temporary has a type of 'ostringstream' not 'ostream'? I can cast the temporary to force the correct operator call too! f(static_cast<std::ostringstream&>(static_cast<std::ostringstream&>(std::ostringstream()) << "Value: " << 5).str().c_str()); This appears to work and passes "Value: 5" to f(). 3) Am I relying on undefined behavior now? The casts look unusual. I'm aware the best alternative is something like this: std::ostringstream ss; ss << "Value: " << 5; f(ss.str().c_str()); ...but I'm interested in the behavior of doing it in one line. Suppose someone wanted to make a (dubious) macro: #define make_temporary_cstr(x) (static_cast<std::ostringstream&>(static_cast<std::ostringstream&>(std::ostringstream()) << x).str().c_str()) // ... f(make_temporary_cstr("Value: " << 5)); Would this function as expected?

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• regex to break a string into "key" / "value" pairs when # of pairs is variable?

  - by user141146

  Hi, I'm using Ruby 1.9 and I'm wondering if there's a simple regex way to do this. I have many strings that look like some variation of this: str = "Allocation: Random, Control: Active Control, Endpoint Classification: Safety Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment" The idea is that I'd like to break this string into its functional components Allocation: Random Control: Active Control Endpoint Classification: Safety Study Intervention Model: Parallel Assignment Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes, Assessor) Primary Purpose: Treatment The "syntax" of the string is that there is a "key" which consists of one or more "words or other characters" (e.g. Intervention Model) followed by a colon (:). Each key has a corresponding "value" (e.g., Parallel Assignment) that immediately follows the colon (:)…The "value" consists of words, commas (whatever), but the end of the "value" is signaled by a comma. The # of key/value pairs is variable. I'm also assuming that colons (:) aren't allowed to be part of the "value" and that commas (,) aren't allowed to be part of the "key". One would think that there is a "regexy" way to break this into its component pieces, but my attempt at making an appropriate matching regex only picks up the first key/value pair and I'm not sure how to capture the others. Any thoughts on how to capture the other matches? regex = /(([^,]+?): ([^:]+?,))+?/ => /(([^,]+?): ([^:]+?,))+?/ irb(main):139:0> str = "Allocation: Random, Control: Active Control, Endpoint Classification: Safety Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment" => "Allocation: Random, Control: Active Control, Endpoint Classification: Safety Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment" irb(main):140:0> str.match regex => #<MatchData "Allocation: Random," 1:"Allocation: Random," 2:"Allocation" 3:" Random,"> irb(main):141:0> $1 => "Allocation: Random," irb(main):142:0> $2 => "Allocation" irb(main):143:0> $3 => " Random," irb(main):144:0> $4 => nil

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• Bound DataGridView not updating data source

  - by Max Yaffe

  I'm trying to bind a table of structures to a DataGridView. Loading and viewing the table is working fine but I can't edit a value and get it stored back into the table. Here's what I'm doing. I have a "primitive" data type, Real defined by public struct MyReal:IMyPrimative { public Double m_Real; //... public MyReal(String val) { m_Real = default(Double); Init(val); } //... } It gets used in a structure: public struct MyReal_Record : IMyRecord { public MyReal Freq { get; set;} MyReal_Record(String[] vals) { Init(vals); } } And the structure is used to define a table using a generic Binding List public class MyTable<S> : BindingList<S> where S: struct, IMyRecord { public Type typeofS; public MyTable() { typeofS = typeof(S); // ... } This table is used as a binding source for a grid, dynamically. private void miLoadFile_Click(object sender, EventArgs e) { MyModel.Table<Real_Record> RTable = new MyModel.Table<Real_Record>(); //... Table initialized here //set up grid with virtual mode dataGridView1.DataSource = RTable; } All of this works fine and I can create RTable, initialize it and display it in a grid. The grid allows editing and has events set for CellParsing and CellFormatting which look like: private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e) { if (e.DesiredType != typeof(String)) return; e.Value = e.Value.ToString(); } private void dataGridView1_CellParsing(object sender, DataGridViewCellParsingEventArgs e) { if (e.DesiredType != typeof(MyReal)) return; e.Value = new MyReal(e.Value.ToString()); e.ParsingApplied = true; this.dataGridView1.UpdateCellValue(e.ColumnIndex, e.RowIndex); } When I edit a value in a cell, I can change the text. On leaving the cell, CellParsing fires and the event handler is called. Everything seems to be correct going into the CellParsing handler. e.DesiredType is MyReal. e.Value is a string with the new value. After the new MyReal is created from the string, e.Value is set correctly. RowIndex and ColumnIndex are correct. ReadOnly is set false. However, when I leave the cell, the system restores the original value to the cell. I thought the UpdateCellValue would replace the value in the dataSource but I seem to be missing something. What did I miss? Thanks, Max

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• Question about DBD::CSB Statement-Functions

  - by sid_com

  From the SQL::Statement::Functions documentation: Function syntax When using SQL::Statement/SQL::Parser directly to parse SQL, functions (either built-in or user-defined) may occur anywhere in a SQL statement that values, column names, table names, or predicates may occur. When using the modules through a DBD or in any other context in which the SQL is both parsed and executed, functions can occur in the same places except that they can not occur in the column selection clause of a SELECT statement that contains a FROM clause. # valid for both parsing and executing SELECT MyFunc(args); SELECT * FROM MyFunc(args); SELECT * FROM x WHERE MyFuncs(args); SELECT * FROM x WHERE y < MyFuncs(args); # valid only for parsing (won't work from a DBD) SELECT MyFunc(args) FROM x WHERE y; Reading this I would expect that the first SELECT-statement of my example shouldn't work and the second should but it is quite the contrary. #!/usr/bin/env perl use warnings; use strict; use 5.010; use DBI; open my $fh, '>', 'test.csv' or die $!; say $fh "id,name"; say $fh "1,Brown"; say $fh "2,Smith"; say $fh "7,Smith"; say $fh "8,Green"; close $fh; my $dbh = DBI->connect ( 'dbi:CSV:', undef, undef, { RaiseError => 1, f_ext => '.csv', }); my $table = 'test'; say "\nSELECT 1"; my $sth = $dbh->prepare ( "SELECT MAX( id ) FROM $table WHERE name LIKE 'Smith'" ); $sth->execute (); $sth->dump_results(); say "\nSELECT 2"; $sth = $dbh->prepare ( "SELECT * FROM $table WHERE id = MAX( id )" ); $sth->execute (); $sth->dump_results(); outputs: SELECT 1 '7' 1 rows SELECT 2 Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2893. DBD::CSV::db prepare failed: Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2894. [for Statement "SELECT * FROM test WHERE id = MAX( id )"] at ./so_3.pl line 30. DBD::CSV::db prepare failed: Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2894. [for Statement "SELECT * FROM test WHERE id = MAX( id )"] at ./so_3.pl line 30. Could someone explaine me this behavior?

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• Instagram API and Zend/Loader.php

  - by Jaemin Kim

  I want to use Instagram API and I found this code. <html> <head></head> <body> <h1>Popular on Instagram</h1> <?php // load Zend classes require_once 'Zend/Loader.php'; Zend_Loader::loadClass('Zend_Http_Client'); // define consumer key and secret // available from Instagram API console $CLIENT_ID = 'YOUR-CLIENT-ID'; $CLIENT_SECRET = 'YOUR-CLIENT-SECRET'; try { // initialize client $client = new Zend_Http_Client('https://api.instagram.com/v1/media/popular'); $client->setParameterGet('client_id', $CLIENT_ID); // get popular images // transmit request and decode response $response = $client->request(); $result = json_decode($response->getBody()); // display images $data = $result->data; if (count($data) > 0) { echo '<ul>'; foreach ($data as $item) { echo '<li style="display: inline-block; padding: 25px"><a href="' . $item->link . '"><img src="' . $item->images->thumbnail->url . '" /></a> <br/>'; echo 'By: <em>' . $item->user->username . '</em> <br/>'; echo 'Date: ' . date ('d M Y h:i:s', $item->created_time) . '<br/>'; echo $item->comments->count . ' comment(s). ' . $item->likes->count . ' likes. </li>'; } echo '</ul>'; } } catch (Exception $e) { echo 'ERROR: ' . $e->getMessage() . print_r($client); exit; } ?> </body> </html> In here, I found Zender/Load.php, and I've never heard about that. Is it okay to go http://www.zend.com/en/products/guard/downloads here, and download Zend for linux?? And for another question, is this code available to use Instagram API?? For last, could you let me know that is there any simple code to use Instagram API? Thank you.

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• Getting jQuery slideshow animation to stop on click

  - by hollyb

  I have a slide show built with jQuery that pauses on hover. It has a group of thumbnails sitting on top of the image that advances the image when clicked, otherwise the slideshow just auto-rotates through all the images. There is also a +/- to expand and contract a caption related to each image. I want to have the slideshow's automatic advancing to stop if one of the thumbnails is clicked, or the +/-. Basically, just stop whenever a user clicks anywhere within the gallery (div class=".homeImg"). I'm having a major brain fart in getting this working properly and could use some advice. Here's the jQuery: $(document).ready(function() { $(".main_image .desc").show(); //Show image info $(".main_image .block").animate({ opacity: 0.85 }, 1 ); //Set Opacity //Click and Hover events for thumbnail list $(".image_thumb ul li:first").addClass('active'); // * Adds a class 'last' to the last li to let the rotator know when to return to the first $(".image_thumb ul li:last").addClass('last'); $(".image_thumb ul li").click(function(){ //Set Variables var imgAlt = $(this).find('img').attr("alt"); //Get Alt Tag of Image var imgTitle = $(this).find('a').attr("href"); //Get Main Image URL var imgDesc = $(this).find('.block').html(); //Get HTML of block var imgDescHeight = $(".main_image").find('.block').height(); //Calculate height of block if ($(this).is(".active")) { //If it's already active, then… return false; // Don't click through } else { //Animate $(".main_image img").animate({ opacity: 0}, 800 ); $(".main_image .block").animate({ opacity: 0, marginBottom: -imgDescHeight }, 800, function() { $(".main_image .block").html(imgDesc).animate({ opacity: 0.85, marginBottom: "0" }, 250 ); $(".main_image img").attr({ src: imgTitle , alt: imgAlt}).animate({ opacity: 1}, 250 ); }); } $(".image_thumb ul li").removeClass('active'); //Remove class of 'active' on all lists $(this).addClass('active'); //add class of 'active' on this list only return false; }) .hover(function(){ $(this).addClass('hover'); }, function() { $(this).removeClass('hover'); }); //Toggle teaser $("a.collapse").click(function(){ $(".main_image .block").slideToggle(); $("a.collapse").toggleClass("show"); return false; // added to remove # browser jump }); // If we are hovering over the image area, pause the clickNext function pauseClickNext = false; $(".homeImg").hover( function () { pauseClickNext = true; }, function () { pauseClickNext = false; } ); // Define function to click the next li var clickNext = function(){ if(!pauseClickNext) { /// find the next li after .active var $next_li = $("li.active").next("li"); if($("li.active").hasClass("last") ){ $(".image_thumb ul li:first").trigger("click"); } else { $next_li.trigger("click"); } } }; // Time between image transition setInterval(clickNext, 6000); });

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• Error in Print Function in Bubble Sort MIPS?

  - by m00nbeam360

  Sorry that this is such a long block of code, but do you see any obvious syntax errors in this? I feel like the problem is that the code isn't printing correctly since the sort and swap methods were from my textbook. Please help if you can! .data save: .word 1,2,4,2,5,6 size: .word 6 .text swap: sll $t1, $a1, 2 #shift bits by 2 add $t1, $a1, $t1 #set $t1 address to v[k] lw $t0, 0($t1) #load v[k] into t1 lw $t2, 4($t1) #load v[k+1] into t1 sw $t2, 0($t1) #swap addresses sw $t0, 4($t1) #swap addresses jr $ra #return sort: addi $sp, $sp, -20 #make enough room on the stack for five registers sw $ra, 16($sp) #save the return address on the stack sw $s3, 12($sp) #save $s3 on the stack sw $s2, 8($sp) #save Ss2 on the stack sw $s1, 4($sp) #save $s1 on the stack sw $s0, 0($sp) #save $s0 on the stack move $s2, $a0 #copy the parameter $a0 into $s2 (save $a0) move $s3, $a1 #copy the parameter $a1 into $s3 (save $a1) move $s0, $zero #start of for loop, i = 0 for1tst: slt $t0, $s0, $s3 #$t0 = 0 if $s0 S $s3 (i S n) beq $t0, $zero, exit1 #go to exit1 if $s0 S $s3 (i S n) addi $s1, $s0, -1 #j - i - 1 for2tst: slti $t0, $s1, 0 #$t0 = 1 if $s1 < 0 (j < 0) bne $t0, $zero, exit2 #$t0 = 1 if $s1 < 0 (j < 0) sll $t1, $s1, 2 #$t1 = j * 4 (shift by 2 bits) add $t2, $s2, $t1 #$t2 = v + (j*4) lw $t3, 0($t2) #$t3 = v[j] lw $t4, 4($t2) #$t4 = v[j+1] slt $t0, $t4, $t3 #$t0 = 0 if $t4 S $t3 beq $t0, $zero, exit2 #go to exit2 if $t4 S $t3 move $a0, $s2 #1st parameter of swap is v(old $a0) move $a1, $s1 #2nd parameter of swap is j jal swap #swap addi $s1, $s1, -1 j for2tst #jump to test of inner loop j print exit2: addi $s0, $s0, 1 #i = i + 1 j for1tst #jump to test of outer loop exit1: lw $s0, 0($sp) #restore $s0 from stack lw $s1, 4($sp) #resture $s1 from stack lw $s2, 8($sp) #restore $s2 from stack lw $s3, 12($sp) #restore $s3 from stack lw $ra, 16($sp) #restore $ra from stack addi $sp, $sp, 20 #restore stack pointer jr $ra #return to calling routine .data space:.asciiz " " # space to insert between numbers head: .asciiz "The sorted numbers are:\n" .text print:add $t0, $zero, $a0 # starting address of array add $t1, $zero, $a1 # initialize loop counter to array size la $a0, head # load address of print heading li $v0, 4 # specify Print String service syscall # print heading out: lw $a0, 0($t0) # load fibonacci number for syscall li $v0, 1 # specify Print Integer service syscall # print fibonacci number la $a0, space # load address of spacer for syscall li $v0, 4 # specify Print String service syscall # output string addi $t0, $t0, 4 # increment address addi $t1, $t1, -1 # decrement loop counter bgtz $t1, out # repeat if not finished jr $ra # return

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• Autoconf -- including a static library (newbie)

  - by EB

  I am trying to migrate my application from manual build to autoconf, which is working very nicely so far. But I have one static library that I can't figure out how to integrate. That library will NOT be located in the usual library locations - the location of the binary (.a file) and header (.h file) will be given as a configure argument. (Notably, even if I move the .a file to /usr/lib or anywhere else I can think of, it still won't work.) It is also not named traditionally (it does not start with "lib" or "l"). Manual compilation is working with these (directory is not predictable - this is just an example): gcc ... -I/home/john/mystuff /home/john/mystuff/helper.a (Uh, I actually don't understand why the .a file is referenced directly, not with -L or anything. Yes, I have a half-baked understanding of building C programs.) So, in my configure.ac, I can use the relevant configure argument to successfully find the header (.h file) using AC_CHECK_HEADER. Inside the AC_CHECK_HEADER I then add the location to CPFLAGS and the #include of the header file in the actual C code picks it up nicely. Given a configure argument that has been put into $location and the name of the needed files are helper.h and helper.a (which are both in the same directory), here is what works so far: AC_CHECK_HEADER([$location/helper.h], [AC_DEFINE([HAVE_HELPER_H], [1], [found helper.h]) CFLAGS="$CFLAGS -I$location"]) Where I run into difficulties is getting the binary (.a file) linked in. No matter what I try, I always get an error about undefined references to the function calls for that library. I'm pretty sure it's a linkage issue, because I can fuss with the C code and make an intentional error in the function calls to that library which produces earlier errors that indicate that the function prototypes have been loaded and used to compile. I tried adding the location that contains the .a file to LDFLAGS and then doing a AC_CHECK_LIB but it is not found. Maybe my syntax is wrong, or maybe I'm missing something more fundamental, which would not be surprising since I'm a newbie and don't really know what I'm doing. Here is what I have tried: AC_CHECK_HEADER([$location/helper.h], [AC_DEFINE([HAVE_HELPER_H], [1], [found helper.h]) CFLAGS="$CFLAGS -I$location"; LDFLAGS="$LDFLAGS -L$location"; AC_CHECK_LIB(helper)]) No dice. AC_CHECK_LIB is looking for -lhelper I guess (or libhelper?) so I'm not sure if that's a problem, so I tried this, too (omit AC_CHECK_LIB and include the .a directly in LDFLAGS), without luck: AC_CHECK_HEADER([$location/helper.h], [AC_DEFINE([HAVE_HELPER_H], [1], [found helper.h]) CFLAGS="$CFLAGS -I$location"; LDFLAGS="$LDFLAGS -L$location/helper.a"]) To emulate the manual compilation, I tried removing the -L but that doesn't help: AC_CHECK_HEADER([$location/helper.h], [AC_DEFINE([HAVE_HELPER_H], [1], [found helper.h]) CFLAGS="$CFLAGS -I$location"; LDFLAGS="$LDFLAGS $location/helper.a"]) I tried other combinations and permutations, but I think I might be missing something more fundamental....

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• In Ruby, how does coerce() actually work?

  - by Jian Lin

  It is said that when we have a class Point and knows how to perform point * 3 like the following: class Point def initialize(x,y) @x, @y = x, y end def *(c) Point.new(@x * c, @y * c) end end point = Point.new(1,2) p point p point * 3 Output: #<Point:0x336094 @x=1, @y=2> #<Point:0x335fa4 @x=3, @y=6> but then, 3 * point is not understood: Point can't be coerced into Fixnum (TypeError) So we need to further define an instance method coerce: class Point def coerce(something) [self, something] end end p 3 * point Output: #<Point:0x3c45a88 @x=3, @y=6> So it is said that 3 * point is the same as 3.*(point) that is, the instance method * takes an argument point and invoke on the object 3. Now, since this method * doesn't know how to multiply a point, so point.coerce(3) will be called, and get back an array: [point, 3] and then * is once again applied to it, is that true? point * 3 which is the same as point.*(3) and now, this is understood and we now have a new Point object, as performed by the instance method * of the Point class. The question is: 1) who invokes point.coerce(3) ? Is it Ruby automatically, or is it some code inside of * method of Fixnum by catching an exception? Or is it by case statement that when it doesn't know one of the known types, then call coerce? 2) Does coerce always need to return an array of 2 elements? Can it be no array? Or can it be an array of 3 elements? 3) And is the rule that, the original operator (or method) * will then be invoked on element 0, with the argument of element 1? (element 0 and element 1 are the two elements in that array returned by coerce) Who does it? Is it done by Ruby or is it done by code in Fixnum? If it is done by code in Fixnum, then it is a "convention" that everybody follows when doing a coerce? So could it be the code in * of Fixnum do something like this: if (something.typeof? ...) else if ... # other type else if ... # other type else # if it is not a type I know array = something.coerce(self) return array[0].*(array[1]) end

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• What is a proper way to store site-level global variables in a SharePoint site?

  - by ccomet

  One thing that has driven me nuts about SharePoint2007 is the apparent inability to have defineable settings that apply specifically to a site or site collection itself, and not the content. I mean, you have some pre-defined settings like the Site Logo, the Site Name, and various other things, but there doesn't appear to be anywhere to add new kinds of settings. The application I am working on needs to be able to create multiple kinds of "project site collections" that all follow a basic template, but have certain additional settings that apply specifically to that site collection and that one alone. In addition to the standard site name we also need to define the Project Number, the Project Name, and the Client Name. And given the requests of some of our clients, we also reach a point where we have to have configurable settings that alter how some of the workflows work, like whether files are marked with Letters or Numbers. Our current solution, which I'm hesitant about, has been to store an XML file on the SharePoint server. This file contains one node for each site collection, identified by the URL of the root site. Inside the node are all of the elements that need to be defined for that site collection. When we need them, we have to access the XML file (which will always require SPSecurity.RunWithElevatedPrivileges to access files right on the server) every time to load it and retrieve the data. There are a lot of automated processes which will have to do this, and I'm hesitant about the stability of this method when we reach hundreds of sites with thousands of files running tens of thousands of workflows, all wanting to access this file. Maybe they're unfounded worries, but I'd rather worry than risk everything breaking in a couple years. I was looking into the SPWeb object and found the AllProperties hashtable. It looks like just the kind of thing which might work, but I don't know how safe it is to be modifying this. I read through both MSDN and the WSS SDK but found nothing that clarified on adding completely new properties into AllProperties. Is it safe to use AllProperties for this kind of thing? Or is there yet another feature that I am missing, which could handle the concept of global variables at the site collection or site scope?

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• Overwhelmed by design patterns... where to begin?

  - by Pete

  I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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• C++ Virtual Constructor, without clone()

  - by Julien L.

  I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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• C++ adding friend to a template class in order to typecast

  - by user1835359

  I'm currently reading "Effective C++" and there is a chapter that contains code similiar to this: template <typename T> class Num { public: Num(int n) { ... } }; template <typename T> Num<T> operator*(const Num<T>& lhs, const Num<T>& rhs) { ... } Num<int> n = 5 * Num<int>(10); The book says that this won't work (and indeed it doesn't) because you can't expect the compiler to use implicit typecasting to specialize a template. As a soluting it is suggested to use the "friend" syntax to define the function inside the class. //It works template <typename T> class Num { public: Num(int n) { ... } friend Num operator*(const Num& lhs, const Num& rhs) { ... } }; Num<int> n = 5 * Num<int>(10); And the book suggests to use this friend-declaration thing whenever I need implicit conversion to a template class type. And it all seems to make sense. But why can't I get the same example working with a common function, not an operator? template <typename T> class Num { public: Num(int n) { ... } friend void doFoo(const Num& lhs) { ... } }; doFoo(5); This time the compiler complaints that he can't find any 'doFoo' at all. And if i declare the doFoo outside the class, i get the reasonable mismatched types error. Seems like the "friend ..." part is just being ignored. So is there a problem with my understanding? What is the difference between a function and an operator in this case?

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• Sorting a list of colors in one dimension?

  - by Ptah- Opener of the Mouth

  I would like to sort a one-dimensional list of colors so that colors that a typical human would perceive as "like" each other are near each other. Obviously this is a difficult or perhaps impossible problem to get "perfectly", since colors are typically described with three dimensions, but that doesn't mean that there aren't some sorting methods that look obviously more natural than others. For example, sorting by RGB doesn't work very well, as it will sort in the following order, for example: (1) R=254 G=0 B=0 (2) R=254 G=255 B=0 (3) R=255 G=0 B=0 (4) R=255 G=255 B=0 That is, it will alternate those colors red, yellow, red, yellow, with the two "reds" being essentially imperceivably different than each other, and the two yellows also being imperceivably different from each other. But sorting by HLS works much better, generally speaking, and I think HSL even better than that; with either, the reds will be next to each other, and the yellows will be next to each other. But HLS/HSL has some problems, too; things that people would perceive as "black" could be split far apart from each other, as could things that people would perceive as "white". Again, I understand that I pretty much have to accept that there will be some splits like this; I'm just wondering if anyone has found a better way than HLS/HSL. And I'm aware that "better" is somewhat arbitrary; I mean "more natural to a typical human". For example, a vague thought I've had, but have not yet tried, is perhaps "L is the most important thing if it is very high or very low", but otherwise it is the least important. Has anyone tried this? Has it worked well? What specifically did you decide "very low" and "very high" meant? And so on. Or has anyone found anything else that would improve upon HSL? I should also note that I am aware that I can define a space-filling curve through the cube of colors, and order them one-dimensionally as they would be encountered while travelling along that curve. That would eliminate perceived discontinuities. However, it's not really what I want; I want decent overall large-scale groupings more than I want perfect small-scale groupings. Thanks in advance for any help.

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• How can I refactor this JavaScript code to avoid making functions in a loop?

  - by Bungle

  I wrote the following code for a project that I'm working on: var clicky_tracking = [ ['related-searches', 'Related Searches'], ['related-stories', 'Related Stories'], ['more-videos', 'More Videos'], ['web-headlines', 'Publication'] ]; for (var x = 0, length_x = clicky_tracking.length; x < length_x; x++) { links = document.getElementById(clicky_tracking[x][0]) .getElementsByTagName('a'); for (var y = 0, length_y = links.length; y < length_y; y++) { links[y].onclick = (function(name, url) { return function() { clicky.log(url, name, 'outbound'); }; }(clicky_tracking[x][1], links[y].href)); } } What I'm trying to do is: define a two-dimensional array, with each instance the inner arrays containing two elements: an id attribute value (e.g., "related-searches") and a corresponding description (e.g., "Related Searches"); for each of the inner arrays, find the element in the document with the corresponding id attribute, and then gather a collection of all <a> elements (hyperlinks) within it; loop through that collection and attach an onclick handler to each hyperlink, which should call clicky.log, passing in as parameters the description that corresponds to the id (e.g., "Related Searches" for the id "related-searches") and the value of the href attribute for the <a> element that was clicked. Hopefully that wasn't thoroughly confusing! The code may be more self-explanatory than that. I believe that what I've implemented here is a closure, but JSLint complains: http://img.skitch.com/20100526-k1trfr6tpj64iamm8r4jf5rbru.png So, my questions are: How can I refactor this code to make JSLint agreeable? Or, better yet, is there a best-practices way to do this that I'm missing, regardless of what JSLint thinks? Should I rely on event delegation instead? That is, attaching onclick event handlers to the document elements with the id attributes in my arrays, and then looking at event.target? I've done that once before and understand the theory, but I'm very hazy on the details, and would appreciate some guidance on what that would look like - assuming this is a viable approach. Thanks very much for any help!

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