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• cross-platform development for mobile devices

  - by user924

  What language/framework is best worth learning for mobile application development? My specific situation is that I'm very familiar with Java and C++ (I especially love Qt), but have limited experience with other languages. Some options I'm considering: 1) Learn Objective-C and all the iPhone-specific tools I do have access to a mac. The downside here is I'm restricted to the iPhone, so I'd have to rewrite almost everything if I wanted to branch off into another mobile device (or move later to a cross-platform framework). Even after knowing Objective-C, it seems like other frameworks might be more efficient/faster to code in? 2) Use some existing cross-platform framework for development I've looked at rhomobile, but I only have limited experience with Ruby (and at first glance, it might be a little pricey comapred to other options). Appcelerator also looks popular and nice, but it uses html/css/javascript. Airplaysdk looks good, but it's new and I haven't been able to see much written about it (is it worth going for?). 3) Wait for something better to come along How far away is Qt for the iPhone? That would be ideal, but it isn't available now. So what do you recommend? Productivity/efficiency is my top priority, although learning a useful language for the long term would also be okay. Thanks

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• Pass an array from IronRuby to C#

  - by cgyDeveloper

  I'm sure this is an easy fix and I just can't find it, but here goes: I have a C# class (let's call it Test) in an assembly (let's say SOTest.dll). Here is something along the lines of what I'm doing: private List<string> items; public List<string> list_items() { return this.items; } public void set_items(List<string> new_items) { this.items = new_items; } In the IronRuby interpreter I run: >>> require "SOTest.dll" true >>> include TestNamespace Object >>> myClass = Test.new TestNamespace.Test >>> myClass.list_items() ['Apples', 'Oranges', 'Pears'] >>> myClass.set_items ['Peaches', 'Plums'] TypeError: can't convert Array into System::Collections::Generic::List(string) I get a similar error whether I make the argument a 'List< string ', 'List< object ' or 'string[ ]'. What is the proper syntax? I can't find a documented mapping of types anywhere (because it's likely too complicated to define in certain scenarios given what Ruby can do).

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• Heroku: Postgres type operator error after migrating DB from MySQL

  - by sevennineteen

  This is a follow-up to a question I'd asked earlier which phrased this as more of a programming problem than a database problem. http://stackoverflow.com/questions/2935985/postgres-error-with-sinatra-haml-datamapper-on-heroku I believe the problem has been isolated to the storage of the ID column in Heroku's Postgres database after running db:push. In short, my app runs properly on my original MySQL database, but throws Postgres errors on Heroku when executing any query on the ID column, which seems to have been stored in Postgres as TEXT even though it is stored as INT in MySQL. My question is why the ID column is being created as INT in Postgres on the data transfer to Heroku, and whether there's any way for me to prevent this. Here's the output from a heroku console session which demonstrates the issue: Ruby console for myapp.heroku.com >> Post.first.title => "Welcome to First!" >> Post.first.title.class => String >> Post.first.id => 1 >> Post.first.id.class => Fixnum >> Post[1] PostgresError: ERROR: operator does not exist: text = integer LINE 1: ...", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Query: SELECT "id", "name", "email", "url", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER BY "id" LIMIT 1 Thanks!

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• Want to add a functional language to my toolchest. Haskell or Erlang?

  - by sean.johnson

  I've been an OO/procedural guy my whole career except in school where I did a lot of logic programming (Prolog). I work on an amazing variety of projects (freelancer) and so I don't want the tools I know and understand to hold me back from using the right tool for the job. I've decided I should know a functional programming language. I've narrowed the field to Haskell and Erlang. What are the pros and cons, advantages and disadvantages, and major trade offs of Haskell and Erlang? How do I decide in a rational way, which is the better path? This is a big time investment, so I'd like to chose wisely. Is there a good case to be made for something else entirely? F#, Scala Ocaml? (BTW, I'm normally a Ruby/C/Obj.C guy, so I'm not terribly impressed or dependent on the JVM as a runtime. It's completely neutral to me. It's a fine runtime, I don't hold it for or against a language. I don't use Microsoft products though, so a .NET runtime would be a negative.)

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• Displaying performance metrics in a modern web app?

  - by Charles

  We're updating our ancient internal PHP application at work. Right now, we gather extensive performance measurements on every pageview, and log them to the database. Additionally, users requested that some of the metrics be displayed at the bottom of the page. This worked out pretty well for us, because the last thing that the application does on every request is include the file containing the HTML footer. The updated parts of the application use an MVC framework and a Dispatch/Request/Response loop. The page footer is no longer the last thing done. In fact, it could very well be the first thing done, before the rest of the page is created. Because we can grab the Response before it's returned to the user, we could try to include placeholders for the performance metrics in the footer and simply replace them with the actual numbers, but this strikes me as a bad idea somehow. How do you handle this in your modern web app? While we're using PHP, I'm curious how it's done in a Ruby/Rails app, and in your favorite Python framework.

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• Programming texts and reference material for my Kindle DX, creating the ultimate reference device?

  - by mwilliams

  (Revisiting this topic with the release of the Kindle DX) Having owned both generation Kindle readers and now getting a Kindle DX; I'm very excited for true PDF handling on an e-ink device! An image of _Why's book on my Kindle (from my iPhone). This gives me a device capable of storing hundreds of thousands of pages that are full text search capable in the form factor of a magazine. What references (preferably PDF to preserve things such as code samples) would you recommend? Ultimately I would like reference material for every modern and applicable programming language (C, C++, Objective-C, Python, Ruby, Java, .NET (C#, Visual Basic, ASP.NET), Erlang, SQL references) as well as general programming texts and frameworks (algorithms, design patterns, theory, Rails, Django, Cocoa, ORMs, etc) and anything else that could be thought of. With so many developers here using such a wide array of languages, as a professional in your particular field, what books or references would you recommend to me for my Kindle? Creative Commons material a plus (translate that to free) as well as the material being in the PDF file format. File size is not an issue. If this turns out to be a success, I will update with a follow-up with a compiled list generated from all of the answers. Thanks for the assistance and contributing! UPDATE I have been using the Kindle DX a lot now for technical books. Check out this blog post I did for high resolution photos of different material: http://www.matthewdavidwilliams.com/2009/06/12/technical-document-pdfs-on-the-kindle-dx/

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• Learning PHP - start out using a framework or no?

  - by Kevin Torrent

  I've noticed a lot of jobs in my area for PHP. I've never used PHP before, and figure if I can get more opportunities if I pick it up then it might be a good idea. The problem is that PHP without any framework is ugly and 99% of the time really bad code. All the tutorials and books I've seen are really lousy - it never shows any kind of good programming practice but always the quick and dirty kind of way of doing things. I'm afraid that trying to learn PHP this way will just imprint these bad practices in my head and make me waste time later trying to unlearn them. I've used C# in the past so I'm familiar with OOP and software design patterns and similar. Should I be trying to learn PHP by using one of the better known frameworks for it? I've looked at CakePHP, Symfony and the Zend Framework so far; Zend seems to be the most flexible without being too constraining like Cake and Symfony (although Symfony seemed less constraining than CakePHP which is trying too hard to be Ruby on Rails), but many tutorials for Zend I've seen assume you already know PHP and want to learn to use the framework. What would be my best opportunity for learning PHP, but learning GOOD PHP that uses real software engineering techniques instead of spaghetti code? It seems all the PHP books and resources either assume you are just using raw PHP and therefore showcase bade practices, or that you already know PHP and therefore don't even touch on parts of the language.

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• client-side data storage and retrieval with html and javascript

  - by pedalpete

  I'm building what I am hoping to be a fairly simple, quick and dirty demo app. So far, I've managed to build a bunch of components using only html and javascript. I know that eventually I'll hook-up a db, but at this point I'm just trying to show off some functionality. In the page, a user can select a bunch of other users (like friends). Then they go to a separate html page and there is some sorting info based on the selected users. So my first attempt was to put the selected users object into a cookie, and retrieve the cookie on the second page. Unfortunately, if the user changed their selection, the cookie wasn't getting updated, and my searches on StackOverflow seemed to say that deleting and updating cookies is unreliable. I tried function updateCookie(updatedUserList){ jQuery.cookie('userList',null); jQuery.cookie('userList',updatedUserList); } but though it set the cookie to null, it wouldn't update it on the second value. So I decided to put the selected users object into a form. Unfortunately, it looks like I can't retrieve the contents from the form on the client-side, only on the server-side. Is there another way to do this? I've worked in PHP and Rails, but I'm trying to do this quickly and simply before building it out into something larger and am trying to avoid any server-side processing for now, which I have managed to do up to this point.

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• How can I use TDD to solve a puzzle with an unknown answer?

  - by matthewsteele

  Recently I wrote a Ruby program to determine solutions to a "Scramble Squares" tile puzzle: I used TDD to implement most of it, leading to tests that looked like this: it "has top, bottom, left, right" do c = Cards.new card = c.cards[0] card.top.should == :CT card.bottom.should == :WB card.left.should == :MT card.right.should == :BT end This worked well for the lower-level "helper" methods: identifying the "sides" of a tile, determining if a tile can be validly placed in the grid, etc. But I ran into a problem when coding the actual algorithm to solve the puzzle. Since I didn't know valid possible solutions to the problem, I didn't know how to write a test first. I ended up writing a pretty ugly, untested, algorithm to solve it: def play_game working_states = [] after_1 = step_1 i = 0 after_1.each do |state_1| step_2(state_1).each do |state_2| step_3(state_2).each do |state_3| step_4(state_3).each do |state_4| step_5(state_4).each do |state_5| step_6(state_5).each do |state_6| step_7(state_6).each do |state_7| step_8(state_7).each do |state_8| step_9(state_8).each do |state_9| working_states << state_9[0] end end end end end end end end end So my question is: how do you use TDD to write a method when you don't already know the valid outputs? If you're interested, the code's on GitHub: Tests: https://github.com/mattdsteele/scramblesquares-solver/blob/master/golf-creator-spec.rb Production code: https://github.com/mattdsteele/scramblesquares-solver/blob/master/game.rb

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• Etiquette: Version bump my fork of opensource project?

  - by Ross

  This question is about etiquette and open source projects. I have forked an application from github and added two new features. The first feature has been request frequently elsewhere. I have added it. Code & implementation are clean (I think). The second feature is more of a hack. It will be of use to others, but the implementation is a little dirty in useage and more so in code. I need the feature but I don't have the skills to fully implement it properly or to a level that could be considered a worth while contrabution to the main project. How should the versioning work? Do I just bump up my version numbers care-free and push to my master branch? It is annoying to know which version is running, modifed or original, as both have the same version number. But will it be confusing when, months later, my github page has a version number the same as the original but both are actually completely different. (I have made pull requests etc. but that is not the context of my question.) The project I have forked uses ruby jeweler so has a versioning format of: Jeweler tracks the version of your project. It assumes you will be using a version in the format x.y.z. x is the 'major' version, y is the 'minor' version, and z is the patch version. Is this standard for other projects/langauges too? Are my changes patches? Thanks

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• Am I a dinosaur programmer?

  - by dlb

  I have been a professional programmer for more than 30 years, and have chosen a career path involving hands-on programming. Programming is something that I love, and I take great pride in the fact that I have continued to keep up to date with current technology. Projects on which I have worked include large enterprise projects as well as smaller desktop programs. The problem I am facing is that I do not have any web-based experience other than some web services. Most of the jobs now available have some web component. I have now been out of work for a year and a half, and have been keeping busy by studying technology that will bridge that gap: CSS, Java Script, JQuery, and Ruby on Rails; AJAX is next. Hiring managers give no consideration whatsoever to the studying that I have been doing. I know that I cannot compete at a senior software level, but companies will not hire someone with my experience at a more junior level. Is there any way to break out of this Catch 22?

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• C++ class derivation and superconstructor confusion

  - by LukeN

  Hey, in a tutorial C++ code, I found this particular piece of confusion: PlasmaTutorial1::PlasmaTutorial1(QObject *parent, const QVariantList &args) : Plasma::Applet(parent, args), // <- Okay, Plasma = namespace, Applet = class m_svg(this), // <- A member function of class "Applet"? m_icon("document") // <- ditto? { m_svg.setImagePath("widgets/background"); // this will get us the standard applet background, for free! setBackgroundHints(DefaultBackground); resize(200, 200); } I'm not new to object oriented programming, so class derivation and super-classes are nothing complicated, but this syntax here got me confused. The header file defines the class like this: class PlasmaTutorial1 : public Plasma::Applet { Similar to above, namespace Plasma and class Applet. But what's the public doing there? I fear that I already know the concept but don't grasp the C++ syntax/way of doing it. In this question I picked up that these are called "superconstructors", at least that's what stuck in my memory, but I don't get this to the full extend. If we glance back at the first snippet, we see Constructor::Class(...) : NS::SuperClass(...), all fine 'till here. But what are m_svg(this), m_icon("document") doing there? Is this some kind of method to make these particular functions known to the derivated class? Is this part of C++ basics or more immediate? While I'm not completly lost in C++, I feel much more at home in C :) Most of the OOP I have done so far was done in D, Ruby or Python. For example in D I would just define class MyClass : MySuperClass, override what I needed to and call the super class' constructor if I'd need to.

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• how to connect to MSSQL using activerecord, JDBC, JTDS and Integrated Security

  - by Rob

  As per the above, I've tried: establish_connection(:adapter => "jdbcmssql", :url => "jdbc:jtds:sqlserver://myserver:1433/mydatabase;domain='mynetwork';", :username => 'user', :password=>'pass' ) establish_connection(:adapter => "jdbcmssql", :url => 'jdbc:jtds:sqlserver://myserver:1433/mydatabase;domain="mynetwork";user="mynetwork\user"' ) establish_connection(:adapter => "jdbcmssql", :url => "jdbc:jtds:sqlserver://myserver:1433/mydatabase;domain='mynetwork';", :username=>'user' ) establish_connection(:adapter => "jdbcmssql", :url => "jdbc:jtds:sqlserver://myserver:1433/mydatabase;domain='mynetwork';integratedSecurity='true'", :username=>'user' ) .. and various other combinations. Each time I get: net/sourceforge/jtds/jdbc/SQLDiagnostic.java:368:in `addDiagnostic': java.sql.SQLException: Login failed for user ''. The user is not associated with a trusted SQL Server connection. (NativeException) Any tips? Thanks, activerecord (2.3.5) activerecord-jdbc-adapter (0.9.6) activerecord-jdbcmssql-adapter (0.9.6) jdbc-jtds (1.2.5) jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2009-11-02 69fbfa3) (Java HotSpot(TM) Client VM 1.6.0_18) [x86-java]

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• Prototype: Form.serialize missing some inputs (due to table?)

  - by Chris

  I'm using JavaScript Prototype (through Ruby on Rails) to handle some Ajax calls; but in one particular case I'm missing a field from the form. I have a layout like this: +---------+---------+ | Thing 1 | Thing 2 | +---------+---------+-----------+ | o Opt 1 | o Opt 1 | <Confirm> | | o Opt 2 | o Opt 2 | | +---------+---------+-----------+ Opt 1 and 2 are Radio buttons, Confirm is a button. The entire table is wrapped in a form, with code like: <form action="javascript:void(0)"> <input type="hidden" name="context" value="foo" /> <input type="hidden" name="subcontext" value="bar" /> <table> <tr><td>Thing 1</td><td>Thing2</td></tr> <tr><td> <input type="radio" name="choice" value="1.1" />Opt 1<br /> <input type="radio" name="choice" value="1.2" />Opt 2<br /> </td><td> <input type="radio" name="choice" value="2.1" />Opt 1<br /> <input type="radio" name="choice" value="2.2" />Opt 2<br /> </td><td> <input name="choice_btn" type="button" value="Confirm" onclick="new AJAX.Updater('my_form', '/process_form', {asynchronous:true, evalScripts:true, parameters:Form.serialize(this.form)}); return false;" /> </td></tr> </table> </form> But I can see that the POST generated by clicking the Confirm button contains the foo and bar values for the hidden fields, but not the choice of the radio buttons. Is this because I've got a table inside my form? How can I get around this?

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• Is there a better way to write this repetitive event-declaration code in C# when implementing an int

  - by Damien Wildfire

  I have a lot of code like the following, where I explicitly implement some events required by an interface. public class IMicrowaveNotifier { event EventHandler<EventArgs> DoorClosed; event EventHandler<EventArgs> LightbulbOn; // ... } public class Microwave : IMicrowaveNotifier { private EventHandler<EventArgs> _doorClosed; event EventHandler<EventArgs> IMicrowaveNotifier.DoorClosed { add { lock (this) _doorClosed += value; } remove { lock (this) _doorClosed -= value; } } private EventHandler<EventArgs> _lightbulbOn; event EventHandler<EventArgs> IMicrowaveNotifier.LightbulbOn { add { lock (this) _lightbulbOn += value; } remove { lock (this) _lightbulbOn -= value; } } // ... } You can see that much of this is boilerplate. In Ruby I'd be able to do something like this: class Microwave has_events :door_closed, :lightbulb_on, ... end Is there a similar shorter way of removing this boilerplate in C#? Update: I left a very important part out of my example: namely, the events getting implemented are part of an interface, and I want to implement it explicitly. Sorry for not mentioning this earlier!

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• DRY jQuery for RESTful PUT/DELETE links

  - by Aupajo

  I'm putting together PUT/DELETE links, a la Rails, which when clicked create a POST form with an hidden input labelled _method that sends the intended request type. I want to make it DRYer, but my jQuery knowledge isn't up to it. HTML: <a href="/articles/1" class="delete">Destroy Article 1</a> <a href="/articles/1/publish" class="put">Publish Article 1</a> jQuery: $(document).ready(function() { $('.delete').click(function() { if(confirm('Are you sure?')) { var f = document.createElement('form'); $(this).after($(f).attr({ method: 'post', action: $(this).attr('href') }).append('<input type="hidden" name="_method" value="DELETE" />')); $(f).submit(); } return false; }); $('.put').click(function() { var f = document.createElement('form'); $(this).after($(f).attr({ method: 'post', action: $(this).attr('href') }).append('<input type="hidden" name="_method" value="PUT" />')); $(f).submit(); return false; }); });

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• Best (functional?) programming language to learn coming from Mathematica

  - by Will Robertson

  As a mechanical engineering PhD student, I haven't had a great pedigree in programming as part of my “day job”. I started out in Matlab (having written some Hypercard and Applescript back in the day, and being introduced to Ada, of all things, in my 1st undergrad year), learned to program—if you can call it that—in (La)TeX; and finally discovered and fell for Mathematica. Now I'm interested in learning a "real" programming language that I can enjoy in the same sort of style as Mathematica, which tries to stress functional programming since it seems to map more nicely to how certain kinds of mathematics can be written algorithmically. So which functional language should I learn? I guess the obvious answer is “as many as possible”, but let's start out humble and give a single, well-considered option a good crack. I've heard good things about, say, Haskell and Scala, but I wonder if (given my non–computer science background) I'd be better off starting in more “grounded” territory and going with Ruby or Python (the latter having the big advantage of being used for Sage, which I'd also like to investigate…after my PhD). Well, I guess this is pretty subjective, so perhaps I could rephrase: would it be better to start looking at Haskell (say) straight after an ad-hoc education to functional programming in Mathematica, or will I get more out of learning Python (say) first? In reference to the question "what do I want to do with it?", I guess my answer is "fun, and learning more". I've got this list of languages that I'd like to look at, and I don't know how to trim them down. And I'd rather start with something a little higher-level than C simply so that I can be somewhat productive without having to re-invent many wheels for any code I'd like to write.

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• How to translate the fields of a database model?

  - by Tõnis M

  I have some tables/models in a web app that will have multilingual content. For example a university, with it's description in a default language(english) and the user wants he can see the same information in another language( if the object has it's fields translated). If there were only a few languages then I would just add fields like name_en and name_de and so on, but the number of languages isn't fixed, so that' would create a mess. I could also just create a new object with the translated data but then foreign keys wouldn't work, and only some of the fields can be translated so that would create duplicate data. Storing the translations in a file and using gettext or something similar is also not an option since the objects fields can be translated by the website user, not only developers/admins. What would be the best way to design/architect such a database? Searching from the translated data should also be not too complex - as it should not require creating complex joins which would make the queries slower I'm using PostgreSQL and Ruby of Rails but I'm not looking for a technical solution but for a general idea how to design it.

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• Java: over-typed structures?

  - by HH

  Term over-type structure = a data structure that accepts different types, can be primitive or user-defined. I think ruby supports many types in structures such as tables. I tried a table with types 'String', 'char' and 'File' in Java but errs. How can I have over-typed structure in Java? How to show types in declaration? What about in initilization? Suppose a structure: INDEX VAR FILETYPE //0 -> file FILE //1 -> lineMap SizeSequence //2 -> type char //3 -> binary boolean //4 -> name String //5 -> path String Code import java.io.*; import java.util.*; public class Object { public static void print(char a) { System.out.println(a); } public static void print(String s) { System.out.println(s); } public static void main(String[] args) { Object[] d = new Object[6]; d[0] = new File("."); d[2] = 'T'; d[4] = "."; print(d[2]); print(d[4]); } } Errors Object.java:18: incompatible types found : java.io.File required: Object d[0] = new File("."); ^ Object.java:19: incompatible types found : char required: Object d[2] = 'T'; ^

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• What's a good way to write batch scripts in C#?

  - by Scott Bilas

  I would like to write simple scripts in C#. Stuff I would normally use .bat or 4NT .btm files for. Copying files, parsing text, asking user input, and so on. Fairly simple but doing this stuff right in a batch file is really hard (no exceptions for example). I'm familiar with command line "scripting" wrappers like AxScript so that gets me part of the way there. What I'm missing is the easy file-manipulation framework. I want to be able to do cd(".."), copy(srcFile, destFile) type functionality. Tools I have tried: NANT, which we use in our build process. Not a good scripting tool. Insanely verbose XML syntax and to add a simple function you must write an extension assembly. Can't do it inline. PowerShell. Looks great, but I just haven't been able to switch over to this as my primary shell. Too many differences from 4NT. Whatever I do needs to run from an ordinary command prompt and not require a special shell to run it through. Can PowerShell be used as a script executor? Perl/Python/Ruby. Really hate learning an entirely new language and framework just to do batch file operations. Haven't been able to dedicate the time I need to do this. Plus, we're a 99% .NET shop for our toolchain and I really want to leverage our existing experience and codebase. Are there frameworks out there that are trying to solve this problem of "make a batch file in C#" that you have used? I want the power of C#/.NET with the immediate-mode type functionality of a typical cmd.exe shell language. Am I alone in wanting something like this?

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• I want to build a Google-friendly web app, where should I start?

  - by ronii

  I have only very basic experience with HTML/CSS and have quite a bit of experience with testing software and web apps from a consumer perspective. I'd love to launch a web application that plays nicely with Google services, similar to some of the apps you'd find on the Google Apps Marketplace, such as ManyMoon, time to note, Socialwok, etc. I'm a huge Google fan and would like to build something that's well integrated with other Google services. If you were a total beginner and wanted to build a complex app like one of examples above (project management, CRM, etc), where would you start? If you worked your ass off 18 hours a day, 24/7, how fast could you do it? I've dabbled into various languages and development frameworks, and read about which apps are using what languages but it's hard to figure out what would be most beneficial to jump into. Ruby on Rails, PHP, Google Web Toolkit, AppEngine. The list goes on and on. I want to be able to build and launch my own scalable web app. Thanks.

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• Should I learn two (or more) programming languages in parallel?

  - by c_maker

  I found entries on this site about learning a new programming language, however, I have not come across anything that talks about the advantages and disadvantages of learning two languages at the same time. Let's say my goal is to learn two new languages in a year. I understand that the definition of learning a new language is different for everyone and you can probably never know everything about a language. I believe in most cases the following things are enough to include the language in your resume and say that you are proficient in it (list is not in any particular order): Know its syntax so you can write a simple program in it Compare its underlying concepts with concepts of other languages Know best practices Know what libraries are available Know in what situations to use it Understand the flow of a more complex program At least know most of what you do not know I would probably look for a good book and pick an open source project for both of these languages to start with. My questions: Is it best to spend 5 months learning language#1 then 5 months learning language#2, or should you mix the two. Mixing them I mean you work on them in parallel. Should you pick two languages that are similar or different? Are there any advantages/disadvantages of let's say learning Lisp in tandem with Ruby? Is it a good idea to pick two languages with similar syntax or would it be too confusing? Please tell me what your experiences are regarding this. Does it make a difference if you are a beginner or a senior programmer?

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• C++ and its type system: How to deal with data with multiple types?

  - by sub

  "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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• How to Check Authenticity of an AJAX Request

  - by Alex Reisner

  I am designing a web site in which users solve puzzles as quickly as they can. JavaScript is used to time each puzzle, and the number of milliseconds is sent to the server via AJAX when the puzzle is completed. How can I ensure that the time received by the server was not forged by the user? I don't think a session-based authenticity token (the kind used for forms in Rails) is sufficient because I need to authenticate the source of a value, not just the legitimacy of the request. Is there a way to cryptographically sign the request? I can't think of anything that couldn't be duplicated by a hacker. Is any JavaScript, by its exposed, client-side nature, subject to tampering? Am I going to have to use something that gets compiled, like Flash? (Yikes.) Or is there some way to hide a secret key? Or something else I haven't thought of? Update: To clarify, I don't want to penalize people with slow network connections (and network speed should be considered inconsistent), so the timing needs to be 100% client-side (the timer starts only when we know the user can see the puzzle). Also, there is money involved so no amount of "trusting the user" is acceptable.

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• Build system for multi-language project

  - by Epcylon

  I am getting ready to embark on a project mainly for experimenting with languages, but also with a hint of usefulness. It will consist of a server-application, written in Erlang, and client-libraries in a number of languages. Initially I will want to write clients in Java, Ruby and Python. The actual protocol for communication will be Thrift. I'm looking for a build system that will allow me to build the server and all the client libraries in one go, running unit-tests in each language, then packaging up a releasable artifact of some sort in whatever way is the "standard" for each language. That means a Jar for Java, a RubyGem and a distribute/setuptools tarball for Python. Erlang probably has something too, but I'm not yet familiar with that. It should also be able to run the Thrift compiler to generate the various Thrift-stubs in each language. On the pad at the start is Maven. I'm fairly certain Maven can do all I need, but I fear it's too Java-centric, and leaves me with a ton of work for every new language I need to add.

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