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  • How to use interfaces in exception handling

    - by vikp
    Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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  • White-box testing in Javascript - how to deal with privacy?

    - by Max Shawabkeh
    I'm writing unit tests for a module in a small Javascript application. In order to keep the interface clean, some of the implementation details are closed over by an anonymous function (the usual JS pattern for privacy). However, while testing I need to access/mock/verify the private parts. Most of the tests I've written previously have been in Python, where there are no real private variables (members, identifiers, whatever you want to call them). One simply suggests privacy via a leading underscore for the users, and freely ignores it while testing the code. In statically typed OO languages I suppose one could make private members accessible to tests by converting them to be protected and subclassing the object to be tested. In Javascript, the latter doesn't apply, while the former seems like bad practice. I could always wall back to black box testing and simply check the final results. It's the simplest and cleanest approach, but unfortunately not really detailed enough for my needs. So, is there a standard way of keeping variables private while still retaining some backdoors for testing in Javascript?

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  • Use of Java [Interfaces / Abstract classes]

    - by Samuel
    Hello, Lately i decided to take a look at Java so i am still pretty new to it and also to the approach of OO programming, so i wanted to get some things straight before learning more, (i guess it's never to soon to start with good practices). I am programming a little 2D game for now but i think my question applies to any non trivial project. For the simplicity i'll provide examples from my game. I have different kinds of zombies, but they all have the same attributes (x, y, health, attack etc) so i wrote an interface Zombie which i implement by WalkingZombie, RunningZombie TeleportingZombie etc. Is this the best thing to do? Am i better of with an abstract class? Or with a super class? (I am not planning to partially implement functions - therefor my choice for an interface instead of an abstract class) I have one class describing the main character (Survivor) and since it is pretty big i wanted to write an interface with the different functions, so that i can easily see and share the structure of it. Is it good practice? Or is it simply a waste of space and time? I hope this question will not be rated as subjective because i thought that experienced programmers won't disagree about this kind of topic since the use of interfaces / super classes / abstract classes follows logical rules and is thereby not simply a personal choice. Thank you for your time -Samuel

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  • Which PHP MVC Framework should I use with MongoDB?

    - by Justin Jenkins
    I have a number of smaller scale PHP projects lined up and would like to take advangtage of a framework. I've read these questions ... What PHP framework would you choose for a new application and why? Picking a PHP MVC Framework I found them useful but I need more specific opinions; here are my major requirements ... MongoDB support (the more 'built-in' the better, a full ORM is not needed however.) MVC (and nice pretty urls ... if you will ... too!) Must work on Apache (2.2) on Ubuntu (10.04.1 LTS), but nginx is also a nice plus. PHP 5.3 or greater. Nice to haves ... I'd prefer more readable code than lots of "shortcut" shorthand coding (that just ends up confusing me later.) I've used PHP for a number of years, but don't use a lot of it's OO (nor do I really care to.) I really love jQuery, so a framework that "thinks" the same way would be nice. Lightweight, I don't need a ton of features ... I just need to make my life easier. I've briefly looked at Lithium, CakePHP, Vork and Symfony ... What would be the best framework for my needs? EDIT: Also docs are pretty important, documentaction with examples! I can't stand to waste time figuring how to use a framework if it would have taken less time to code it myself.

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  • Object model design choice

    - by spinon
    I am currently working on a ASP.NET MVC reporting application using C#. This is a redesign from a PHP application that was just initially thrown together and is now starting to gain some more traction. SowWe are in the process of reworking the backend to have a more OO approach. One of the descisions I am currently wrestling with is how to structure the domain objects. Since 95% of the site is readonly I am not sure if the typical approaches are practical. Should I create domain objects for the primary pieces of the application (ticket, assignment, assignee) and then create static methods off of these areas to pull the reporting data? Or should I just skip that part and create the chart data classes and have some get method off of these classes? It's not a real big application and currenlty I am the only one developing on it. But I feel torn as to which approach. I feel that the first one is the better choice but maybe overkill given that the majority of uses is for aggregate reporting. Anybody have some good insight on why I should go one way or another?

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  • [Rails3] How to do multiple many to many relationships between the same two tables.

    - by Kurt
    Hi. I have a model of a club where I want to model the two entities Meeting and Member. There are actually two many-to-many relationships between these entities though, as for any meeting a Member can either be a Speaker or a Guest. Now I am an OO thinker, so would normally just create the two classes and each one would just have two arrays of the other inside, but rails is making me think a bit more data centric here, so I realise I need to break these M2M relationships up with join tables Speakers and Guests which I have done, but now I am having trouble describing the relationships in the models. The two join table models both have "belongs_to :meeting" and "belongs_to :member" and I think that should be sufficient. I am not however sure about the Meeting and Member models though. Each one has "has_many :guests" and "has_many: speakers" but I am not sure if I also want to go: has_many :members, :through = :guests has_many :members, :through = :speakers But I suspect that this is like declaring two "members" that will clash. I also thought about: has_many :guests, :through = :guests has_many :speakers, :through = :speakers Does that make sense? How would ActiveRecord know that they are in fact Members? I have found heaps of examples of polymorphic m2m relationships and m2m relationships where 1 table references itself, but no good examples to help me mode this situation where two separate tables have two different m2m relationships. Anyone got any tips?

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  • .NET security mechanism to restrict access between two Types in the same project?

    - by jdk
    Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project. Note: I'm not talking about access modifiers to hide members of a Type from another type - I mean to hide the Type itself. Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the same ASP.NET Website project. In other words I want to fake the layers and have some kind of security mechanism around each layer to prevent it from accessing another. Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. Even something that restricts one namespace from accessing another. I'm unsure the final form it might take. If this were C++ I'd likely be using friend to make as solution, which doesn't translate to C# internal in this case although they're often compared. I don't really care whether the solution actually hides Types from each other or just makes them inaccessible; however I don't want to lock down one Type from all others, another reason access modifiers are not a solution. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ...

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  • How do I subtract two dates in Django/Python?

    - by Ryan
    Hi! I'm working on a little fitness tracker in order to teach myself Django. I want to graph my weight over time, so I've decided to use the Python Google Charts Wrapper. Google charts require that you convert your date into a x coordinate. To do this I want to take the number of days in my dataset by subtracting the first weigh-in from the last weigh-in and then using that to figure out the x coords (for example, I could 100 by the result and increment the x coord by the resulting number for each y coord.) Anyway, I need to figure out how to subtract Django datetime objects from one another and so far, I am striking out on both google and here at the stack. I know PHP, but have never gotten a handle on OO programming, so please excuse my ignorance. Here is what my models look like: class Goal(models.Model): goal_weight = models.DecimalField("Goal Weight",max_digits=4, decimal_places=1) target_date = models.DateTimeField("Target Date to Reach Goal") set_date = models.DateTimeField("When did you set your goal?") comments = models.TextField(blank=True) def __unicode__(self): return unicode(self.goal_weight) class Weight(models.Model): """Weight at a given date and time """ goal = models.ForeignKey(Goal) weight = models.DecimalField("Current Weight",max_digits=4, decimal_places=1) weigh_date = models.DateTimeField("Date of Weigh-In") comments = models.TextField(blank=True) def __unicode__(self): return unicode(self.weight) def recorded_today(self): return self.date.date() == datetime.date.today() Any ideas on how to proceed in the view? Thanks so much!

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  • Refactoring huge if ( ... instanceof ...)

    - by Chris
    I'm currently trying to refactor a part of a project that looks like this: Many classes B extends A; C extends A; D extends C; E extends B; F extends A; ... And somewhere in the code: if (x instanceof B){ B n = (B) x; ... }else if (x instanceof C){ C n = (C) x; ... }else if (x instanceof D){ D n = (D) x; ... }else if (x instanceof E){ E n = (E) x; ... }else if (x instanceof G){ G n = (G) x; ... }... Above if-construct currently sits in a function with a CC of 19. Now my question is: Can I split this if-construct up in mutliple functions and let Java's OO do the magic? Or are there any catches I have to look out for? My idea: private void oopMagic(C obj){ ... Do the stuff from the if(x instanceof C) here} private void oopMagic(D obj){ ... Do the stuff from the if(x instanceof D) here} private void oopMagic(E obj){ ... Do the stuff from the if(x instanceof E) here} .... and instead of the huge if: oopMagic(x);

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  • Dynamic Array of Objects Sans Vector Class

    - by Connor Black
    I am doing a homework assignment for my summer OO class and we need to write two classes. One is called Sale and the other is called Register. I've written my Sale class; here's the .h file: enum ItemType {BOOK, DVD, SOFTWARE, CREDIT}; class Sale { public: Sale(); // default constructor, // sets numerical member data to 0 void MakeSale(ItemType x, double amt); ItemType Item(); // Returns the type of item in the sale double Price(); // Returns the price of the sale double Tax(); // Returns the amount of tax on the sale double Total(); // Returns the total price of the sale void Display(); // outputs sale info private: double price; // price of item or amount of credit double tax; // amount of sales tax double total; // final price once tax is added in. ItemType item; // transaction type }; For the Register class we need to include a dynamic array of Sale objects in our member data. We cannot use the vector class. How is this done? Here's my 'Register' '.h' class Register{ public: Register(int ident, int amount); ~Register(); int GetID(){return identification;} int GetAmount(){return amountMoney;} void RingUpSale(ItemType item, int basePrice); void ShowLast(); void ShowAll(); void Cancel(); int SalesTax(int n); private: int identification; int amountMoney; };

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  • Using enum values to represent binary operators (or functions)

    - by Bears will eat you
    I'm looking for an elegant way to use values in a Java enum to represent operations or functions. My guess is, since this is Java, there just isn't going to be a nice way to do it, but here goes anyway. My enum looks something like this: public enum Operator { LT, LTEQ, EQEQ, GT, GTEQ, NEQ; ... } where LT means < (less than), LTEQ means <= (less than or equal to), etc - you get the idea. Now I want to actually use these enum values to apply an operator. I know I could do this just using a whole bunch of if-statements, but that's the ugly, OO way, e.g.: int a = ..., b = ...; Operator foo = ...; // one of the enum values if (foo == Operator.LT) { return a < b; } else if (foo == Operator.LTEQ) { return a <= b; } else if ... // etc What I'd like to be able to do is cut out this structure and use some sort of first-class function or even polymorphism, but I'm not really sure how. Something like: int a = ..., b = ...; Operator foo = ...; return foo.apply(a, b); or even int a = ..., b = ...; Operator foo = ...; return a foo.convertToOperator() b; But as far as I've seen, I don't think it's possible to return an operator or function (at least, not without using some 3rd-party library). Any suggestions?

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  • What's the difference between UI development and front-end development?

    - by Nick Lowman
    I'm a front-end developer and really enjoy jQuery and JavaScript. I've built a lot a websites, done some good jQuery work and built a few JavaScript based applications and would really like to get in UI development. Or so I thought. I guessed it would be pretty similar to what I already do except maybe a little more JavaScript heavy but when I looked into it all the job specs said I needed to know about Scrum or Agile development, knowledge of testing frameworks and a good knowledge of JavaScript frameworks and custom events. So, from the specs I get the idea that a UI developer is actually a dedicated JavaScript developer. Is that the case? I understand (with much help from the users on stackoverflow), about JavaScript OO, inheritance, closures, custom events, debugging in Firefox or Aptana etc, and the people I work with seem to think I pretty OK at what I do but clearly my knowledge is not good enough to go for UI jobs. If anyone could tell me a little more about UI development and if there are any good resources for learning about it I would be most grateful as I couldn't find much on the internet.

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  • self-destructing objects in php5?

    - by user151841
    I am working on a class in php that is basically an interface to a database row. I wanted to create a delete() method that would 1. delete the database row and 2. destroy the instance of itself so that further attempts to manipulate the row via the object would throw warnings. Doing some googling, it seems that, in php5, it's not possible for an object to unset itself. http://bugs.php.net/bug.php?id=36971 In fact they discuss the very situation I was wanting to do :( So how should I proceed? I could make boolean flag as a class property, for whether the row still exists, and have each operation check that flag and throw an error if the row has been deleted. This maintains the oo structure of code, so I would have $objDbRow->delete(); But then I have to put checks at the beginning of each method. Or, I could implement a __destruct method that deletes the row. But that would seem counter-intuitive to me; if I saw in code unset($objDbRow); All I would suspect that's happening is that the object is being discarded, not that a row is being deleted. So that to me would seem like bad practice.

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  • interface abstract in php real world scenario

    - by jason
    The goal is to learn whether to use abstract or interface or both... I'm designing a program which allows a user to de-duplicate all images but in the process rather then I just build classes I'd like to build a set of libraries that will allow me to re-use the code for other possible future purposes. In doing so I would like to learn interface vs abstract and was hoping someone could give me input into using either. Here is what the current program will do: recursive scan directory for all files determine file type is image type compare md5 checksum against all other files found and only keep the ones which are not duplicates Store total duplicates found at the end and display size taken up Copy files that are not duplicates into folder by date example Year, Month folder with filename is file creation date. While I could just create a bunch of classes I'd like to start learning more on interfaces and abstraction in php. So if I take the scan directory class as the first example I have several methods... ScanForFiles($path) FindMD5Checksum() FindAllImageTypes() getFileList() The scanForFiles could be public to allow anyone to access it and it stores in an object the entire directory list of files found and many details about them. example extension, size, filename, path, etc... The FindMD5Checksum runs against the fileList object created from scanForFiles and adds the md5 if needed. The FindAllImageTypes runs against the fileList object as well and adds if they are image types. The findmd5checksum and findallimagetypes are optionally run methods because the user might not intend to run these all the time or at all. The getFileList returns the fileList object itself. While I have a working copy I've revamped it a few times trying to figure out whether I need to go with an interface or abstract or both. I'd like to know how an expert OO developer would design it and why?

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  • Understanding Basic Prototyping & Updating Key/Value pairs

    - by JordanD
    First time poster, long time lurker. I'm trying to learn some more advanced features of .js, and have two ojectives based on the pasted code below: I would like to add methods to a parent class in a specific way (by invoking prototype). I intend to update the declared key/value pairs each time I make an associated method call. execMTAction as seen in TheSuper will execute each function call, regardless. This is by design. Here is the code: function TheSuper(){ this.options = {componentType: "UITabBar", componentName: "Visual Browser", componentMethod: "select", componentValue: null}; execMTAction(this.options.componentType, this.options.componentName, this.options.componentMethod, this.options.componentValue); }; TheSuper.prototype.tapUITextView = function(val1, val2){ this.options = {componentType: "UITextView", componentName: val1, componentMethod: "entertext", componentValue: val2}; }; I would like to execute something like this (very simple): theSuper.executeMTAction(); theSuper.tapUITextView("a", "b"); Unfortunately I am unable to overwrite the "this.options" in the parent, and the .tapUITextView method throws an error saying it cannot find executeMTAction. All I want to do, like I said, is to update the parameters in the parent, then have executeMTAction run each time I make any method call. That's it. Any thoughts? I understand this is basic but I'm coming from a long-time procedural career and .js seems to have this weird confluence of oo/procedural that I'm having a bit of difficulty with. Thanks for any input!

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  • Another sound not working post

    - by Thomas Smart
    Tried all the other "sound not working" posts i think, lost count. purge/reinstall alsa and pulse, reboot, add user to audio group, various lines in the alsa config file such as "options snd-hda-intel model=" then tried different options like generic, auto, basic, default, etc. tried pulseaudio -k && sudo alsa force-reload a few times, with and without rebooting. Hardware: 16gb ram, core I7-4790, Intel Haswell mboard with onboard sound and graphics Multimedia: Audio Adapter: HDA-Intel-HDA Intel HDMI OS: Ubuntu server 14.04 with ubuntu-desktop installed. GUI sound settings lists only the dummy sound card alsamixer -c 0 ¦ Card: HDA Intel HDMI F1: Help ¦ ¦ Chip: Intel Haswell HDMI F2: System information ¦ ¦ View: F3:[Playback] F4: Capture F5: All F6: Select sound card ¦ ¦ Item: S/PDIF ¦ ¦ +--+ ¦ ¦ ¦OO¦ ¦ ¦ +--+ ¦ ¦ < S/PDIF > ¦ aplay -l **** List of PLAYBACK Hardware Devices **** card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 aplay -L default Playback/recording through the PulseAudio sound server null Discard all samples (playback) or generate zero samples (capture) pulse PulseAudio Sound Server hdmi:CARD=HDMI,DEV=0 HDA Intel HDMI, HDMI 0 HDMI Audio Output dmix:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct sample mixing device dsnoop:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct sample snooping device hw:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct hardware device without any conversions plughw:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Hardware device with all software conversions cat /proc/asound/cards 0 [HDMI ]: HDA-Intel - HDA Intel HDMI HDA Intel HDMI at 0xf7d14000 irq 46 cat /proc/asound/devices 1: : sequencer 2: [ 0- 3]: digital audio playback 3: [ 0- 0]: hardware dependent 4: [ 0] : control 33: : timer mplayer -ao alsa:device=hdmi /usr/share/sounds/ubuntu/stereo/system-ready.ogg MPlayer 1.1-4.8 (C) 2000-2012 MPlayer Team mplayer: could not connect to socket mplayer: No such file or directory Failed to open LIRC support. You will not be able to use your remote control. Playing /usr/share/sounds/ubuntu/stereo/system-ready.ogg. libavformat version 54.20.4 (external) Mismatching header version 54.20.3 libavformat file format detected. [lavf] stream 0: audio (vorbis), -aid 0 Load subtitles in /usr/share/sounds/ubuntu/stereo/ ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version 54.35.0 (external) AUDIO: 44100 Hz, 1 ch, floatle, 80.0 kbit/5.67% (ratio: 10000->176400) Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis) ========================================================================== [AO_ALSA] alsa-lib: confmisc.c:768:(parse_card) cannot find card '1' [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory [AO_ALSA] alsa-lib: confmisc.c:392:(snd_func_concat) error evaluating strings [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory [AO_ALSA] alsa-lib: confmisc.c:1251:(snd_func_refer) error evaluating name [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory [AO_ALSA] alsa-lib: conf.c:4727:(snd_config_expand) Evaluate error: No such file or directory [AO_ALSA] alsa-lib: pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM hdmi [AO_ALSA] Playback open error: No such file or directory Failed to initialize audio driver 'alsa:device=hdmi' Could not open/initialize audio device -> no sound. Audio: no sound Video: no video Exiting... (End of file) mplayer -ao alsa:device=hw=0.3 /usr/share/sounds/ubuntu/stereo/system-ready.ogg MPlayer 1.1-4.8 (C) 2000-2012 MPlayer Team mplayer: could not connect to socket mplayer: No such file or directory Failed to open LIRC support. You will not be able to use your remote control. Playing /usr/share/sounds/ubuntu/stereo/system-ready.ogg. libavformat version 54.20.4 (external) Mismatching header version 54.20.3 libavformat file format detected. [lavf] stream 0: audio (vorbis), -aid 0 Load subtitles in /usr/share/sounds/ubuntu/stereo/ ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version 54.35.0 (external) AUDIO: 44100 Hz, 1 ch, floatle, 80.0 kbit/5.67% (ratio: 10000->176400) Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis) ========================================================================== [AO_ALSA] Format floatle is not supported by hardware, trying default. AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample) Video: no video Starting playback... A: 0.4 (00.4) of 0.8 (00.7) 0.1% Exiting... (End of file) Thank you for your time and help :)

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  • Introducing functional programming constructs in non-functional programming languages

    - by Giorgio
    This question has been going through my mind quite a lot lately and since I haven't found a convincing answer to it I would like to know if other users of this site have thought about it as well. In the recent years, even though OOP is still the most popular programming paradigm, functional programming is getting a lot of attention. I have only used OOP languages for my work (C++ and Java) but I am trying to learn some FP in my free time because I find it very interesting. So, I started learning Haskell three years ago and Scala last summer. I plan to learn some SML and Caml as well, and to brush up my (little) knowledge of Scheme. Well, a lot of plans (too ambitious?) but I hope I will find the time to learn at least the basics of FP during the next few years. What is important for me is how functional programming works and how / whether I can use it for some real projects. I have already developed small tools in Haskell. In spite of my strong interest for FP, I find it difficult to understand why functional programming constructs are being added to languages like C#, Java, C++, and so on. As a developer interested in FP, I find it more natural to use, say, Scala or Haskell, instead of waiting for the next FP feature to be added to my favourite non-FP language. In other words, why would I want to have only some FP in my originally non-FP language instead of looking for a language that has a better support for FP? For example, why should I be interested to have lambdas in Java if I can switch to Scala where I have much more FP concepts and access all the Java libraries anyway? Similarly: why do some FP in C# instead of using F# (to my knowledge, C# and F# can work together)? Java was designed to be OO. Fine. I can do OOP in Java (and I would like to keep using Java in that way). Scala was designed to support OOP + FP. Fine: I can use a mix of OOP and FP in Scala. Haskell was designed for FP: I can do FP in Haskell. If I need to tune the performance of a particular module, I can interface Haskell with some external routines in C. But why would I want to do OOP with just some basic FP in Java? So, my main point is: why are non-functional programming languages being extended with some functional concept? Shouldn't it be more comfortable (interesting, exciting, productive) to program in a language that has been designed from the very beginning to be functional or multi-paradigm? Don't different programming paradigms integrate better in a language that was designed for it than in a language in which one paradigm was only added later? The first explanation I could think of is that, since FP is a new concept (it isn't new at all, but it is new for many developers), it needs to be introduced gradually. However, I remember my switch from imperative to OOP: when I started to program in C++ (coming from Pascal and C) I really had to rethink the way in which I was coding, and to do it pretty fast. It was not gradual. So, this does not seem to be a good explanation to me. Or can it be that many non-FP programmers are not really interested in understanding and using functional programming, but they find it practically convenient to adopt certain FP-idioms in their non-FP language? IMPORTANT NOTE Just in case (because I have seen several language wars on this site): I mentioned the languages I know better, this question is in no way meant to start comparisons between different programming languages to decide which is better / worse. Also, I am not interested in a comparison of OOP versus FP (pros and cons). The point I am interested in is to understand why FP is being introduced one bit at a time into existing languages that were not designed for it even though there exist languages that were / are specifically designed to support FP.

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  • Functional programming constructs in non-functional programming languages

    - by Giorgio
    This question has been going through my mind quite a lot lately and since I haven't found a convincing answer to it I would like to know if other users of this site have thought about it as well. In the recent years, even though OOP is still the most popular programming paradigm, functional programming is getting a lot of attention. I have only used OOP languages for my work (C++ and Java) but I am trying to learn some FP in my free time because I find it very interesting. So, I started learning Haskell three years ago and Scala last summer. I plan to learn some SML and Caml as well, and to brush up my (little) knowledge of Scheme. Well, a lot of plans (too ambitious?) but I hope I will find the time to learn at least the basics of FP during the next few years. What is important for me is how functional programming works and how / whether I can use it for some real projects. I have already developed small tools in Haskell. In spite of my strong interest for FP, I find it difficult to understand why functional programming constructs are being added to languages like C#, Java, C++, and so on. As a developer interested in FP, I find it more natural to use, say, Scala or Haskell, instead of waiting for the next FP feature to be added to my favourite non-FP language. In other words, why would I want to have only some FP in my originally non-FP language instead of looking for a language that has a better support for FP? For example, why should I be interested to have lambdas in Java if I can switch to Scala where I have much more FP concepts and access all the Java libraries anyway? Similarly: why do some FP in C# instead of using F# (to my knowledge, C# and F# can work together)? Java was designed to be OO. Fine. I can do OOP in Java (and I would like to keep using Java in that way). Scala was designed to support OOP + FP. Fine: I can use a mix of OOP and FP in Scala. Haskell was designed for FP: I can do FP in Haskell. If I need to tune the performance of a particular module, I can interface Haskell with some external routines in C. But why would I want to do OOP with just some basic FP in Java? So, my main point is: why are non-functional programming languages being extended with some functional concept? Shouldn't it be more comfortable (interesting, exciting, productive) to program in a language that has been designed from the very beginning to be functional or multi-paradigm? Don't different programming paradigms integrate better in a language that was designed for it than in a language in which one paradigm was only added later? The first explanation I could think of is that, since FP is a new concept (it isn't new at all, but it is new for many developers), it needs to be introduced gradually. However, I remember my switch from imperative to OOP: when I started to program in C++ (coming from Pascal and C) I really had to rethink the way in which I was coding, and to do it pretty fast. It was not gradual. So, this does not seem to be a good explanation to me. Also, I asked myself if my impression is just plainly wrong due to lack of knowledge. E.g., do C# and C++11 support FP as extensively as, say, Scala or Caml do? In this case, my question would be simply non-existent. Or can it be that many non-FP programmers are not really interested in using functional programming, but they find it practically convenient to adopt certain FP-idioms in their non-FP language? IMPORTANT NOTE Just in case (because I have seen several language wars on this site): I mentioned the languages I know better, this question is in no way meant to start comparisons between different programming languages to decide which is better / worse. Also, I am not interested in a comparison of OOP versus FP (pros and cons). The point I am interested in is to understand why FP is being introduced one bit at a time into existing languages that were not designed for it even though there exist languages that were / are specifically designed to support FP.

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  • Project structure: where to put business logic

    - by Mister Smith
    First of all, I'm not asking where does business logic belong. This has been asked before and most answers I've read agree in that it belongs in the model: Where to put business logic in MVC design? How much business logic should be allowed to exist in the controller layer? How accurate is "Business logic should be in a service, not in a model"? Why put the business logic in the model? What happens when I have multiple types of storage? However people disagree in the way this logic should be distributed across classes. There seem to exist three major currents of thought: Fat model with business logic inside entity classes. Anemic model and business logic in "Service" classes. It depends. I find all of them problematic. The first option is what most Fowlerites stick to. The problem with a fat model is that sometimes a business logic funtion is not only related to a class, and instead uses a bunch of other classes. If, for example, we are developing a web store, there should be a function that calcs an order's total. We could think of putting this function inside the Order class, but what actually happens is that the logic needs to use different classes, not only data contained in the Order class, but also in the User class, the Session class, and maybe the Tax class, Country class, or Giftcard, Payment, etc. Some of these classes could be composed inside the Order class, but some others not. Sorry if the example is not very good, but I hope you understand what I mean. Putting such a function inside the Order class would break the single responsibility principle, adding unnecesary dependences. The business logic would be scattered across entity classes, making it hard to find. The second option is the one I usually follow, but after many projects I'm still in doubt about how to name the class or classes holding the business logic. In my company we usually develop apps with offline capabilities. The user is able to perform entire transactions offline, so all validation and business rules should be implemented in the client, and then there's usually a background thread that syncs with the server. So we usually have the following classes/packages in every project: Data model (DTOs) Data Access Layer (Persistence) Web Services layer (Usually one class per WS, and one method per WS method). Now for the business logic, what is the standard approach? A single class holding all the logic? Multiple classes? (if so, what criteria is used to distribute the logic across them?). And how should we name them? FooManager? FooService? (I know the last one is common, but in our case it is bad naming because the WS layer usually has classes named FooWebService). The third option is probably the right one, but it is also devoid of any useful info. To sum up: I don't like the first approach, but I accept that I might have been unable to fully understand the Zen of it. So if you advocate for fat models as the only and universal solution you are welcome to post links explaining how to do it the right way. I'd like to know what is the standard design and naming conventions for the second approach in OO languages. Class names and package structure, in particular. It would also be helpful too if you could include links to Open Source projects showing how it is done. Thanks in advance.

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  • Thoughts on C# Extension Methods

    - by Damon
    I'm not a huge fan of extension methods.  When they first came out, I remember seeing a method on an object that was fairly useful, but when I went to use it another piece of code that method wasn't available.  Turns out it was an extension method and I hadn't included the appropriate assembly and imports statement in my code to use it.  I remember being a bit confused at first about how the heck that could happen (hey, extension methods were new, cut me some slack) and it took a bit of time to track down exactly what it was that I needed to include to get that method back.  I just imagined a new developer trying to figure out why a method was missing and fruitlessly searching on MSDN for a method that didn't exist and it just didn't sit well with me. I am of the opinion that if you have an object, then you shouldn't have to include additional assemblies to get additional instance level methods out of that object.  That opinion applies to namespaces as well - I do not like it when the contents of a namespace are split out into multiple assemblies.  I prefer to have static utility classes instead of extension methods to keep things nicely packaged into a cohesive unit.  It also makes it abundantly clear where utility methods are used in code.  I will concede, however, that it can make code a bit more verbose and lengthy.  There is always a trade-off. Some people harp on extension methods because it breaks the tenants of object oriented development and allows you to add methods to sealed classes.  Whatever.  Extension methods are just utility methods that you can tack onto an object after the fact.  Extension methods do not give you any more access to an object than the developer of that object allows, so I say that those who cry OO foul on extension methods really don't have much of an argument on which to stand.  In fact, I have to concede that my dislike of them is really more about style than anything of great substance. One interesting thing that I found regarding extension methods is that you can call them on null objects. Take a look at this extension method: namespace ExtensionMethods {   public static class StringUtility   {     public static int WordCount(this string str)     {       if(str == null) return 0;       return str.Split(new char[] { ' ', '.', '?' },         StringSplitOptions.RemoveEmptyEntries).Length;     }   }   } Notice that the extension method checks to see if the incoming string parameter is null.  I was worried that the runtime would perform a check on the object instance to make sure it was not null before calling an extension method, but that is apparently not the case.  So, if you call the following code it runs just fine. string s = null; int words = s.WordCount(); I am a big fan of things working, but this seems to go against everything I've come to know about instance level methods.  However, an extension method is really a static method masquerading as an instance-level method, so I suppose it would be far more frustrating if it failed since there is really no reason it shouldn't succeed. Although I'm not a fan of extension methods, I will say that if you ever find yourself at an impasse with a die-hard fan of either the utility class or extension method approach, then there is a common ground.  Extension methods are defined in static classes, and you call them from those static classes as well as directly from the objects they extend.  So if you build your utility classes using extension methods, then you can have it your way and they can have it theirs. 

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  • Surviving MATLAB and R as a Hardcore Programmer

    - by dsimcha
    I love programming in languages that seem geared towards hardcore programmers. (My favorites are Python and D.) MATLAB is geared towards engineers and R is geared towards statisticians, and it seems like these languages were designed by people who aren't hardcore programmers and don't think like hardcore programmers. I always find them somewhat awkward to use, and to some extent I can't put my finger on why. Here are some issues I have managed to identify: (Both): The extreme emphasis on vectors and matrices to the extent that there are no true primitives. (Both): The difficulty of basic string manipulation. (Both): Lack of or awkwardness in support for basic data structures like hash tables and "real", i.e. type-parametric and nestable, arrays. (Both): They're really, really slow even by interpreted language standards, unless you bend over backwards to vectorize your code. (Both): They seem to not be designed to interact with the outside world. For example, both are fairly bulky programs that take a while to launch and seem to not be designed to make simple text filter programs easy to write. Furthermore, the lack of good string processing makes file I/O in anything but very standard forms near impossible. (Both): Object orientation seems to have a very bolted-on feel. Yes, you can do it, but it doesn't feel much more idiomatic than OO in C. (Both): No obvious, simple way to get a reference type. No pointers or class references. For example, I have no idea how you roll your own linked list in either of these languages. (MATLAB): You can't put multiple top level functions in a single file, encouraging very long functions and cut-and-paste coding. (MATLAB): Integers apparently don't exist as a first class type. (R): The basic builtin data structures seem way too high level and poorly documented, and never seem to do quite what I expect given my experience with similar but lower level data structures. (R): The documentation is spread all over the place and virtually impossible to browse or search. Even D, which is often knocked for bad documentation and is still fairly alpha-ish, is substantially better as far as I can tell. (R): At least as far as I'm aware, there's no good IDE for it. Again, even D, a fairly alpha-ish language with a small community, does better. In general, I also feel like MATLAB and R could be easily replaced by plain old libraries in more general-purpose langauges, if sufficiently comprehensive libraries existed. This is especially true in newer general purpose languages that include lots of features for library writers. Why do R and MATLAB seem so weird to me? Are there any other major issues that you've noticed that may make these languages come off as strange to hardcore programmers? When their use is necessary, what are some good survival tips? Edit: I'm seeing one issue from some of the answers I've gotten. I have a strong personal preference, when I analyze data, to have one script that incorporates the whole pipeline. This implies that a general purpose language needs to be used. I hate having to write a script to "clean up" the data and spit it out, then another to read it back in a completely different environment, etc. I find the friction of using MATLAB/R for some of my work and a completely different language with a completely different address space and way of thinking for the rest to be a huge source of friction. Furthermore, I know there are glue layers that exist, but they always seem to be horribly complicated and a source of friction.

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  • Educational, well-written FOSS projects to read, study or discuss

    - by Godot
    Before you say it: yes, this "question" has been asked other times. However, I could not fine many of such questions and not that easily, and those I found had similar results. What I'm trying to say that there are no comprehensive lists of well written Open Source projects, so I decided to set some requirements for the entries (one or possibly more): Idiomatic use of the language in which they are written The project should be lightweight. Not as in "a few kbs", as in "clean" and possibly following the UNIX philosophy, making an efficient use of resources and performing its duty and nothing more. No code bloat, most importantly. Projects like Firefox and GNOME wouldn't qualify, for example. Minimal reliance on external, non-standard libraries, with exceptions for some common FOSS libraries (curses, Xlib, OpenGL and possibly "usual suspects" like gtk+, webkit and Boost). Reliance on well-written libraries is welcome. No reliance on proprietary software - for obvious reasons (programs that rely on XNA, DirectX, Cocoa and similar, for example). Well-documented code is welcome. Include link to web interfaces to their repositories if possible. Here are some sample projects that often pop up in these threads: Operating Systems Plan 9 from Bell Labs: More or less, the official "sequel" to UNIX. Written in C by the same people who invented C! NetBSD: The most portable BSD implementation, written in C and also a good example of portable and organized code. Network and Databases Sqlite: Extremely lightweight and extremely efficient, one of the best pieces of C software I've seen. Count the lines yourself! Lighttpd: A small but pretty reliable web server written in C. Programming languages and VMs Lua: extremely lightweight multi-paradigm programming language. Written in C. Tiny C Compiler: Really tiny C compiler. Not really comparable to GCC or Clang but does its job. PyPy: A Python implementation written in Python. Pharo: OK, I admit it, I'm not really a Smalltalk expert but Pharo is a fork of Squeak and looked rather interesting. Stackless Python - An implementation of Python that doesn't rely on the C call stack - written in C (with some parts in Python) Games and 3D: Angband: One of the most accessible roguelike codebases around here, written in C. Ogre3D: Cross-platform 3D engine. Gets bloated if you don't skip the platform-specific implementation code, otherwise is a pretty solid example of good C++ OO. Simon Tatham's Portable Puzzle Collection: Title says it all. Other - dwm: Lightweight window manager. Written in C. Emulation and Reverse Engineering - Bochs: x86 emulator, written in C++ and tiny enough. - MAME: If you want to see C at one of its lowest levels, MAME is for you. May not be as clean as the other projects but it can teach you A LOT. Before you ask: I didn't mention Linux because it has become quite bloated in the last few years, Linus has also confirmed it. Nonetheless, it'd be a great educational read the same, even if for other reasons. Same for GCC. Feel free to edit or wikify my post. I hope you won't lock my question, I'm only trying to organize a little community effort for the good of all those people who want to enhance their coding skills.

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  • TripleDES in Perl/PHP/ColdFusion

    - by Seidr
    Recently a problem arose regarding hooking up an API with a payment processor who were requesting a string to be encrypted to be used as a token, using the TripleDES standard. Our Applications run using ColdFusion, which has an Encrypt tag - that supports TripleDES - however the result we were getting back was not what the payment processor expected. First of all, here is the resulting token the payment processor were expecting. AYOF+kRtg239Mnyc8QIarw== And below is the snippet of ColdFusion we were using, and the resulting string. <!--- Coldfusion Crypt (here be monsters) ---> <cfset theKey="123412341234123412341234"> <cfset theString = "username=test123"> <cfset strEncodedEnc = Encrypt(theString, theKey, "DESEDE", "Base64")> <!--- resulting string(strEncodedEnc): tc/Jb7E9w+HpU2Yvn5dA7ILGmyNTQM0h ---> As you can see, this was not returning the string we were hoping for. Seeking a solution, we ditched ColdFusion for this process and attempted to reproduce the token in PHP. Now I'm aware that various languages implement encryption in different ways - for example in the past managing encryption between a C# application and PHP back-end, I've had to play about with padding in order to get the two to talk, but my experience has been that PHP generally behaves when it comes to encryption standards. Anyway, on to the PHP source we tried, and the resulting string. /* PHP Circus (here be Elephants) */ $theKey="123412341234123412341234"; $theString="username=test123"; $strEncodedEnc=base64_encode(mcrypt_ecb (MCRYPT_3DES, $theKey, $theString, MCRYPT_ENCRYPT)); /* resulting string(strEncodedEnc): sfiSu4mVggia8Ysw98x0uw== */ As you can plainly see, we've got another string that differs from both the string expected by the payment processor AND the one produced by ColdFusion. Cue head-against-wall integration techniques. After many to-and-fro communications with the payment processor (lots and lots of reps stating 'we can't help with coding issues, you must be doing it incorrectly, read the manual') we were finally escalated to someone with more than a couple of brain-cells to rub together, who was able to step back and actually look at and diagnose the issue. He agreed, our CF and PHP attempts were not resulting in the correct string. After a quick search, he also agreed that it was not neccesarily our source, but rather how the two languages implemented their vision of the TripleDES standard. Coming into the office this morning, we were met by an email with a snippet of source code, in Perl. This is was the code they were directly using on their end to produce the expected token. #!/usr/bin/perl # Perl Crypt Calamity (here be...something) use strict; use CGI; use MIME::Base64; use Crypt::TripleDES; my $cgi = CGI->new(); my $param = $cgi->Vars(); $param->{key} = "123412341234123412341234"; $param->{string} = "username=test123"; my $des = Crypt::TripleDES->new(); my $enc = $des->encrypt3($param->{string}, $param->{key}); $enc = encode_base64($enc); $enc =~ s/\n//gs; # resulting string (enc): AYOF+kRtg239Mnyc8QIarw== So, there we have it. Three languages, three implementations of what they quote in the documentation as TripleDES Standard Encryption, and three totally different resulting strings. My question is, from your experience of these three languages and their implementations of the TripleDES algorithm, have you been able to get any two of them to give the same response, and if so what tweaks to the code did you have to make in order to come to the result? I understand this is a very drawn out question, but I wanted to give clear and precise setting for each stage of testing that we had to perform. I'll also be performing some more investigatory work on this subject later, and will post any findings that I come up with to this question, so that others may avoid this headache.

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  • Asp.net mvc application deployment / security issues

    - by WestDiscGolf
    I'll start with appologies; I wasn't sure if this was best posted here of Server Fault so if its in the wrong place then please move :-) Basic information I have written the first module of a new application at work. This is written using Visual Studio 2010, targetting .net 3.5 (at the moment) and asp.net mvc 2. This has been working fine during development running on the built in Development server from VS but however does not work once deployed to IIS 7/7.5. To deploy the application, I have built it in release mode and created a deployment package by right clicking on the project in the solution explorer (this will be done with an automated build in tfs once upgrade from the beta). This has then been imported into IIS on the server. The application is using windows/domain authentication. Issue #1 I can fire up internet explorer and browse to the application from a client computer as well as on a remote desktop connection. I can execute the code which reads/stores data in Session fine from the IE instance on the remote desktop but if I browse to it from the client pc it seems to lose the session state. I click on the form submit and the page refreshes and doesn't execute the required code. I've tried setting with; InProc, SQLServer and StateServer. but with no luck :-( Issue #2 As part of the application it views PDF and Tiff documents on the fly which are on a network share on the office network and creates thumbnails if the document hasn't been viewed before. This works if running on the machine the application is deployed to; however when browsing from a client pc I get an error saying: Access to the path '\\fileserver\folder\file.tif' is denied Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.UnauthorizedAccessException: Access to the path '\\fileserver\folder\file.TIF' is denied. ASP.NET is not authorized to access the requested resource. Consider granting access rights to the resource to the ASP.NET request identity. ASP.NET has a base process identity (typically {MACHINE}\ASPNET on IIS 5 or Network Service on IIS 6) that is used if the application is not impersonating. If the application is impersonating via , the identity will be the anonymous user (typically IUSR_MACHINENAME) or the authenticated request user. As this is on a different server the user is not accessible. To get round this I have tried: 1 - setting the application pool to run as domain administrator (I know this is a security risk, but I'm just trying to get it to work at the moment!) 2 - to set the log on account for World Wide Web Publishing service to be the domain admin . When trying to restart the service I get ... Windows could not start the World Wide Web Publishing Service service on the Local Computer. Error 1079: The account specified for this service is different from the account specified fro the other services running in the same process. Any pointers/help would be much appriciated as I'm pulling my hair out (of what little I have left). Update I've been using this funky little tool I found - DelegConfig v2 beta (Delegation / Kerberos Configuration Tool). This has been really usefull. So I've got the accessing of the file share working (there is a test page which will read the files) so now I've just got the issue of passing through the users credentials through to the SQL Server (wans't my choice to do it this way!!) to execute the queries etc. but I can't get it to log on as the user. It tries to access it as "NT Authority\Network Service" which doesn't have a sql login (as should be the logged on user). My connection string is: <add name="User" connectionString="Data Source=.;Integrated Security=True" providerName="System.Data.SqlClient" /> No initial catalog is specified as the system is over multiple dbs (also wasn't my choice!!). I really appriciate all the help so far! :-) Any further hints?!

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  • Ada and 'The Book'

    - by Phil Factor
    The long friendship between Charles Babbage and Ada Lovelace created one of the most exciting and mysterious of collaborations ever to have resulted in a technological breakthrough. The fireworks that created by the collision of two prodigious mathematical and creative talents resulted in an invention, the Analytical Engine, which went on to change society fundamentally. However, beyond that, we just don't know what the bulk of their collaborative work was about:;  it was done in strictest secrecy. Even the known outcome of their friendship, the first programmable computer, was shrouded in mystery. At the time, nobody, except close friends and family, had any idea of Ada Byron's contribution to the invention of the ‘Engine’, and how to program it. Her great insight was published in August 1843, under the initials AAL, standing for Ada Augusta Lovelace, her title then being the Countess of Lovelace. It was contained in a lengthy ‘note’ to her translation of a publication that remains the best description of Babbage's amazing Analytical Engine. The secret identity of the person behind those enigmatic initials was finally revealed by Prince de Polignac who, seventy years later, wrote to Ada's daughter to seek confirmation that her mother had, indeed, been the author of the brilliant sentences that described so accurately how Babbage's mechanical computer could be programmed with punch-cards. L.F. Menabrea's paper on the Analytical Engine first appeared in the 'Bibliotheque Universelle de Geneve' in October 1842, and Ada translated it anonymously for Taylor's 'Scientific Memoirs'. Charles Babbage was surprised that she had not written an original paper as she already knew a surprising amount about the way the machine worked. He persuaded her to at least write some explanatory notes. These notes ended up extending to four times the length of the original article and represented the first published account of how a machine could be programmed to perform any calculation. Her example of programming the Bernoulli sequence would have worked on the Analytical engine had the device’s construction been completed, and gave Ada an unassailable claim to have invented the art of programming. What was the reason for Ada's secrecy? She was the only legitimate child of Lord Byron, who was probably the best known celebrity of the age, so she was already famous. She was a senior aristocrat, with titles, a fortune in money and vast estates in the Midlands. She had political influence, and was the cousin of Lord Melbourne, who was the Prime Minister at that time. She was friendly with the young Queen Victoria. Her mathematical activities were a pastime, and not one that would be considered by others to be in keeping with her roles and responsibilities. You wouldn't dare to dream up a fictional heroine like Ada. She was dazzlingly beautiful and talented. She could speak several languages fluently, and play some musical instruments with professional skill. Contemporary accounts refer to her being 'accomplished in science, art and literature'. On top of that, she was a brilliant mathematician, a talent inherited from her mother, Annabella Milbanke. In her mother's circle of literary and scientific friends was Charles Babbage, and Ada's friendship with him dates from her teenage zest for Mathematics. She was one of the first people he'd ever met who understood what he had attempted to achieve with the 'Difference Engine', and with whom he could converse as intellectual equals. He arranged for her to have an education from the most talented academics in the country. Ada melted the heart of the cantankerous genius to the point that he became a faithful and loyal father-figure to her. She was one of the very few who could grasp the principles of the later, and very different, ‘Analytical Engine’ which was designed from the start to tackle a variety of tasks. Sadly, Ada Byron's life ended less than a decade after completing the work that assured her long-term fame, in November 1852. She was dying of cancer, her gambling habits had caused her to run up huge debts, she'd had more than one affairs, and she was being blackmailed. Her brilliant but unempathic mother was nursing her in her final illness, destroying her personal letters and records, and repaying her debts. Her husband was distraught but helpless. Charles Babbage, however, maintained his steadfast paternalistic friendship to the end. She appointed her loyal friend to be her executor. For years, she and Babbage had been working together on a secret project, known only as 'The Book'. We have a clue to what it was in a letter written by her nine years earlier, on 11th August 1843. It was a joint project by herself and Lord Lovelace, her husband, and was intended to involve Babbage's 'undivided energies'. It involved 'consulting your Engine' (it required Babbage’s computer). The letter gives no hint about the project except for the high-minded nature of its purpose, and its highly mathematical nature.  From then on, the surviving correspondence between the two gives only veiled references to 'The Book'. There isn't much, since Babbage later destroyed any letters that could have damaged her reputation within the Establishment. 'I cannot spare the book today, which I am very sorry for. At the moment I want it for constant reference, but I think you can have it tomorrow' (Oct 1844)  And 'I will send you the book directly, and you can say, when you receive it, how long you will want to keep it'. (Nov 1844)  The two of them were obviously intent on the work: She writes, four years later, 'I have an engagement for Wednesday which will prevent me from attending to your wishes about the book' (Dec 1848). This was something that they both needed to work on, but could not do in parallel: 'I will send the book on Tuesday, and it can be left with you till Friday' (11 Feb 1849). After six years work, it had been so well-handled that it was beginning to fall apart: 'Don't forget the new cover you promised for the book. The poor book is very shabby and wants one' (20 Sept 1849). So what was going on? The word 'book' was not a code-word: it was a real book, probably a 'printer's blank', plain paper, but properly bound so printers and publishers could show off how the published work might look. The hints from the correspondence are of advanced mathematics. It is obvious that the book was travelling between them, back and forth, each one working on it for less than a week before passing it back. Ada and her husband were certainly involved in gambling large sums of money on the horses, and so most biographers have concluded that the three of them were trying to calculate the mathematical odds on the horses. This theory has three large problems. Firstly, Ada's original letter proposing the project refers to its high-minded nature. Babbage was temperamentally opposed to gambling and would scarcely have given so much time to the project, even though he was devoted to Ada. Secondly, Babbage would have very soon have realized the hopelessness of trying to beat the bookies. This sort of betting never attracts his type of intellectual background. The third problem is that any work on calculating the odds on horses would not need a well-thumbed book to pass back and forth between them; they would have not had to work in series. The original project was instigated by Ada, along with her husband, William King-Noel, 1st Earl of Lovelace. Charles Babbage was invited to join the project after the couple had come up with the idea. What could William have contributed? One might assume that William was a Bertie Wooster character, addicted only to the joys of the turf, but this was far from the truth. He was a scientist, a Cambridge graduate who was later elected to be a Fellow of the Royal Society. After Eton, he went to Trinity College, Cambridge. On graduation, he entered the diplomatic service and acted as secretary under Lord Nugent, who was Lord Commissioner of the Ionian Islands. William was very friendly with Babbage too, able to discuss scientific matters on equal terms. He was a capable engineer who invented a process for bending large timbers by the application of steam heat. He delivered a paper to the Institution of Civil Engineers in 1849, and received praise from the great engineer, Isambard Kingdom Brunel. As well as being Lord Lieutenant of the County of Surrey for most of Victoria's reign, he had time for a string of scientific and engineering achievements. Whatever the project was, it is unlikely that William was a junior partner. After Ada's death, the project disappeared. Then, two years later, Babbage, through one of his occasional outbursts of temper, demonstrated that he was able to decrypt one of the most powerful of secret codes, Vigenère's autokey cipher.  All contemporary diplomatic and military messages used a variant of this cipher. Babbage had made three important discoveries, namely, the mathematical law of this cipher, the principle of the key periodicity, and the technique of the symmetry of position. The technique is now known as the Kasiski examination, also called the Kasiski test, but Babbage got there first. At one time, he listed amongst his future projects, the writing of a book 'The Philosophy of Decyphering', but it never came to anything. This discovery was going to change the course of history, since it was used to decipher the Russians’ military dispatches in the Crimean war. Babbage himself played a role during the Crimean War as a cryptographical adviser to his friend, Rear-Admiral Sir Francis Beaufort of the Admiralty. This is as much as we can be certain about in trying to make sense of the bulk of the time that Charles Babbage and Ada Lovelace worked together. Nine years of intensive work, involving the 'Engine' and a great deal of mathematics and research seems to have been lost: or has it? I've argued in the past http://www.simple-talk.com/community/blogs/philfactor/archive/2008/06/13/59614.aspx that the cracking of the Vigenère autokey cipher, was a fundamental motive behind the British Government's support and funding of the 'Difference Engine'. The Duke of Wellington, whose understanding of the military significance of being able to read enemy dispatches, was the most steadfast advocate of the project. If the three friends were actually doing the work of cracking codes by mathematical techniques that used the techniques of key periodicity, and symmetry of position (the use of a book being passed quickly to and fro is very suggestive), intending to then use the 'Engine' to do the routine cracking of each dispatch, then this is a rather different story. The project was Ada and William's idea. (William had served in the diplomatic service and would be familiar with the use of codes). This makes Ada Lovelace the initiator of a project which, by giving both Britain, and probably the USA, a diplomatic and military advantage in the second part of the Nineteenth century, changed world history. Ada would never have wanted any credit for cracking the cipher, and developing the method that rendered all contemporary military and diplomatic ciphering techniques nugatory; quite the reverse. And it is clear from the gaps in the record of the letters between the collaborators that the evidence was destroyed, probably on her request by her irascible but intensely honorable executor, Charles Babbage. Charles Babbage toyed with the idea of going public, but the Crimean war put an end to that. The British Government had a valuable secret, and intended to keep it that way. Ada and Charles had quite often discussed possible moneymaking projects that would fund the development of the Analytic Engine, the first programmable computer, but their secret work was never in the running as a potential cash cow. I suspect that the British Government was, even then, working on the concealment of a discovery whose value to the nation depended on it remaining so. The success of code-breaking in the Crimean war, and the American Civil war, led to the British and Americans  subsequently giving much more weight and funding to the science of decryption. Paradoxically, this makes Ada's contribution even closer to the creation of Colossus, the first digital computer, at Bletchley Park, specifically to crack the Nazi’s secret codes.

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