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  • Something confusing about Single Responsibility Principle

    - by user1483278
    1) In fact if two responsibilities are always expected to change at the same time you arguably should not separate them into different classes as this would lead, to quote Martin, to a "smell of Needless Complexity". The same is the case for responsibilities that never change - the behavior is invariant, and there is no need to split it. I assume even if non-related responsibilities are always expected to change for the same reason ( or if they never change ), we still shouldn't put them in the same class, since this would still violate high cohesion principle? 2) I've found two quite different definitions for SRP: Single Responsibility Principle says that a subsystem, module, class, or even a function, should not have more than one reason to change. and There should never be more than one reason for a class to change Doesn't the latter definition narrow SRP to a class level? If so, isn't first quote wrong by claiming that SRP can also be applied at subsystem, module and function levels? thank you

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  • Licensing approach for .NET library that might be used desktop / web-service / cloud environment

    - by Bobrovsky
    I am looking for advice how to architect licensing for a .NET library. I am not asking for tool/service recommendations or something like that. My library can be used in a regular desktop application, in an ASP.NET solution. And now Azure services come into play. Currently, for desktop applications the library checks if the application and company names from the version history are the same as the names the key was generated for. In other cases the library compares hardware IDs. Now there are problems: an Azure-enabled web-application can be run on different hardware each time (AFAIK) sometimes the hardware ID for the same hardware changes unexpectedly checking the hardware ID or version info might not be allowed in some circumstances (shared hosting for example) So, I am thinking about what approach I can take to architect a licensing scheme that: is friendly to customers (I do not try to fight piracy, but I do want to warn the customer if he uses the library on more servers than he paid for) can be used when there is no internet connection can be used on shared hosting What would you recommend?

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  • Examples of Liskov Substitution

    - by james lewis
    I'm facilitating a session next week on the Liskov Substitution Principle and I was wondering if anyone had any examples of violations 'from the trenches'? I'm looking for something other than uncle Bob's rectangle - square problem and the persistent set problem he talks about in A-PPP (although that is a great example). So far I'm using the example of a (very simple) List and an IndexedList as the 'correct' use of inheritance. And the addition of a Set to this hierarchy as a violation (as a Set is distinct; strengthening the pre condition of the Add method). I've also taken this great example and it's solution from this question Both those examples are great but I'm looking for something more subtle and harder to spot. So far I've come up with nothing so if you've got a great, subtle example post it up. Also, any metaphors you've come across that helped you understand LSP would be really useful too.

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  • Javascript Rookie Question: Define Variables Inline

    - by Dylan Kinnett
    I'm proficient with HTML and CSS but I'm still pretty shaky when it comes to Javascript. That said, I've been able to build a site using the Internet Archive Book Reader, which relies on reader.js Here's a copy of one of my versions of reader.js https://gist.github.com/dylan-k/ed4efed2384e221d46cc It's a good site, but I find I have to repeat things a lot. Basically, I have one copy of reader.js for every page/book featured on the site. It seems there must be a better way. I re-use the script, making copies, just so that I can change lines 28, 80, 83, 84. Is there a way I could include just one copy of reader.js and then use a <script> tag to define these 4 lines for the individual pages?

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  • Do you start migrating your Swing project to JavaFX

    - by Yan Cheng CHEOK
    I have a 4 years old project which is written in Swing + SwingX. Currently, it is still alive and still kicking. However, as more GUI related feature requests coming in (For instance, a sortable tree table), I start to feel the difficulty in fulling the requests. This is true especially there isn't active development going around SwingX project. Also, I hardly can find any good, yet being actively maintained/ developed/ evolving GUI Java framework. I was wondering, any of Swing developers feel the same thing? Have you start to migrate your Swing project to a much more active developed GUI framework like JavaFX?

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  • Liskov principle: violation by type-hinting

    - by Elias Van Ootegem
    According to the Liskov principle, a construction like the one below is invalid, as it strengthens a pre-condition. I know the example is pointless/nonsense, but when I last asked a question like this, and used a more elaborate code sample, it seemed to distract people too much from the actual question. //Data models abstract class Argument { protected $value = null; public function getValue() { return $this->value; } abstract public function setValue($val); } class Numeric extends Argument { public function setValue($val) { $this->value = $val + 0;//coerce to number return $this; } } //used here: abstract class Output { public function printValue(Argument $arg) { echo $this->format($arg); return $this; } abstract public function format(Argument $arg); } class OutputNumeric extends Output { public function format(Numeric $arg)//<-- VIOLATION! { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } My question is this: Why would this kind of "violation" be considered harmful? So much so that some languages, like the one I used in this example (PHP), don't even allow this? I'm not allowed to strengthen the type-hint of an abstract method but, by overriding the printValue method, I am allowed to write: class OutputNumeric extends Output { final public function printValue(Numeric $arg) { echo $this->format($arg); } public function format(Argument $arg) { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } But this would imply repeating myself for each and every child of Output, and makes my objects harder to reuse. I understand why the Liskov principle exists, don't get me wrong, but I find it somewhat difficult to fathom why the signature of an abstract method in an abstract class has to be adhered to so much stricter than a non-abstract method. Could someone explain to me why I'm not allowed to hind at a child class, in a child class? The way I see it, the child class OutputNumeric is a specific use-case of Output, and thus might need a specific instance of Argument, namely Numeric. Is it really so wrong of me to write code like this?

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  • Data binding in web UI frameworks, what's the deal?

    - by c-smile
    I believe that most of modern Web frameworks that pretend to be MVC ones also has a notion of data binding in one form or another. Examples: AngularJS, EmberJS, KnockoutJS, etc. I am assuming that "data binding" is a declarative definition (oxymoron, no?) of live link between data (a.k.a. model) and its representation (a.k.a. view). With some transformers in between (a.k.a. controllers). I understand why declarativeness is kind of appealing but also understand that as usual it comes with the price. In particular: 1. Live binding is quite heavy, either with dirty watch (high CPU consumption) or with Object.observe() (high memory consumption with high CPU load in some scenarios). 2. There is a "frame" part in the framework word, means there are some boundaries/limits that can be hard to overcome if you need slightly more than it was designed for. Quite usual time split: 90% of features are made in 10% of project time. But 10% rest take 90% of project time. I suspect (a.k.a. educated guess) that those MVC things are not helping to implement more functionality in less time... If so their usage motivation is not quite clear. As an example: last week wanted to find virtual list idea/solution. Found one in vanilla JavaScript that is 120 LOC. Implementation of the same but in AngualrJS is about 420 LOC. Most of the code there seems like a fight with the framework itself... So is my question: what benefits that MVC stuff or data binding give us? Is it just a buzzword popular among project managers or they give us something useful. If later one then what exactly?

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  • What's the best way to create a static utility class in python? Is using metaclasses code smell?

    - by rsimp
    Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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  • Getting work done in a small office

    - by three-cups
    I work in an office area of ~450sqft. There are a total of 7 people working in the office. I've been finding it hard to concentrate on my work (writing code) because of the distractions going on around me. The distractions are both work-related and non-work-related conversations. I'm trying to figure out what to do in this situation. I want to be part of the team, and I want to get my work done to the best of my ability. I can easily think of two options that I don't like: Stay where I am, not be able to concentrate and get less work done Move somewhere else. (This is tough because I code on a desktop, so I'm not very mobile.) But what are other options? I'm going to talk this through with my team in the next couple days. Any advice or solutions would be great.

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  • How lookaheads are propagated in "channel" method of building LALR parser?

    - by greenoldman
    The method is described in Dragon Book, however I read about it in ""Parsing Techniques" by D.Grune and C.J.H.Jacobs". I start from my understanding of building channels for NFA: channels are built once, they are like water channels with current you "drop" lookahead symbols in right places (sources) of the channel, and they propagate with "current" when symbol propagates, there are no barriers (the only sufficient things for propagation are presence of channel and direction/current); i.e. lookahead cannot just die out of the blue Is that right? If I am correct, then eof lookahead should be present in all states, because the source of it is the start production, and all other production states are reachable from start state. How the DFA is made out of this NFA is not perfectly clear for me -- the authors of the mentioned book write about preserving channels, but I see no purpose, if you propagated lookaheads. If the channels have to be preserved, are they cut off from the source if the DFA state does not include source NFA state? I assume no -- the channels still runs between DFA states, not only within given DFA state. In the effect eof should still be present in all items in all states. But when you take a look at DFA presented in book (pdf is from errata): DFA for LALR (fig. 9.34 in the book, p.301) you will see there are items without eof in lookahead. The grammar for this DFA is: S -> E E -> E - T E -> T T -> ( E ) T -> n So how it was computed, when eof was dropped, and on what condition? Update It is textual pdf, so two interesting states (in DFA; # is eof): State 1: S--- >•E[#] E--- >•E-T[#-] E--- >•T[#-] T--- >•n[#-] T--- >•(E)[#-] State 6: T--- >(•E)[#-)] E--- >•E-T[-)] E--- >•T[-)] T--- >•n[-)] T--- >•(E)[-)] Arc from 1 to 6 is labeled (.

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  • Which version of Java should I use for learning?

    - by Dan
    I am a QA engineer interested in mobile development and automation.I have basic programming experience (intermediate level Python, C++ programmer) and as most companies choose Java for writing frameworks I need to pickup Java. I use Ubutnu 12.04 LTS and I will be using Head First Java as learning material. When I searched for JDK options I found Oracle Java 6 and 7 and Open JDK. I read somewhere in Ubuntu forums that Java 6 is not recommended on Ubuntu systems and I am a little bit confused about which version should I use, that would be compatible with the book and the OS.

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  • Recommendations for adjustable sit-stand workstations?

    - by Chris Phillips
    Recently, I've been feeling the discomfort of sitting at my desk all day long. I'm fairly active, stretch, and take regular breaks, but some days it's still pretty uncomfortable to sit all day long, whether in a nice chair or on an exercise ball. I would really like able to stand at my computer for part of the day. My current setup is a large desk with two 26" lcds and a 17" laptop. I don't mind if the laptop isn't adjustable, as I don't use it as regularly as the monitors. I would like to be able to fairly easily switch from a sitting position to a standing position and back again as necessary. I've been looking into adjustable height desks and stands and found that they tend to be either really expensive, or don't quite meet my needs. (For example, the Ergotron WorkFit-S Dual LCD workstation looks like the ideal feature set at a reasonable price, but won't fit with my monitors.) Any suggestions or thoughts? Update: fixed a typo. Thanks @RDL!

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  • I'm a student learning C++ and I've recently found out about Ruby. Would learning (some of) Ruby help me with C++ or would it just confuse me?

    - by Von32
    Hi! As the title says, I'm a student that will be starting my second year of C++ very soon. I've discovered Ruby, however. While I've heard much buzz about the language before, I've disregarded it because I always thought it wasn't something that would be useful. However, I've found a number of FANTASTIC tutorials on ruby and am interested in learning it (probably because it seems so straightforward). Would playing around with ruby be a good or bad idea? I understand that there's not such thing as bad knowledge, but I'm afraid that Ruby will only confuse me when dealing with C++. How different from C++ is it? I've read it's based on C in some way, but my google-fu seems to be horrible today. How useful is Ruby in the real world? I'm not specifically asking about jobs- I'm more interested in what sort of applications may come from this language. Any specific examples worth looking at? Going back to Question two- I've read some posts on here that Ruby and C++ can hold hands once in a while. How flexible is this relationship? Is it rarely that this would work? Thank you Very much for your time! EDIT: This has to be the one community on the internet that doesn't suck. Why have I never posted before? You guys are awesome!

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  • How can I implement an EPUB reader in JavaScript?

    - by Vlad Nicula
    I'm wondering if I can create an EPUB (free and open e-book standard) reader in JavaScript. The basic requirements would be: Server parts of the EPUB reader from a server API. Read the EPUB data in JavaScript. Render it on page. Provide some extra functionality, like text highlights or page notes. I have no information about how I could do this. I'm willing to try a prototype project. What are the steps that I could take towards implementing such a thing?

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  • Threads are facing deadlock in socket program [migrated]

    - by ankur.trapasiya
    I am developing one program in which a user can download a number of files. Now first I am sending the list of files to the user. So from the list user selects one file at a time and provides path where to store that file. In turn it also gives the server the path of file where does it exist. I am following this approach because I want to give stream like experience without file size limitation. Here is my code.. 1) This is server which gets started each time I start my application public class FileServer extends Thread { private ServerSocket socket = null; public FileServer() { try { socket = new ServerSocket(Utils.tcp_port); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } @Override public void run() { try { System.out.println("request received"); new FileThread(socket.accept()).start(); } catch (IOException ex) { ex.printStackTrace(); } } } 2) This thread runs for each client separately and sends the requested file to the user 8kb data at a time. public class FileThread extends Thread { private Socket socket; private String filePath; public String getFilePath() { return filePath; } public void setFilePath(String filePath) { this.filePath = filePath; } public FileThread(Socket socket) { this.socket = socket; System.out.println("server thread" + this.socket.isConnected()); //this.filePath = filePath; } @Override public void run() { // TODO Auto-generated method stub try { ObjectInputStream ois=new ObjectInputStream(socket.getInputStream()); try { //************NOTE filePath=(String) ois.readObject(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } File f = new File(this.filePath); byte[] buf = new byte[8192]; InputStream is = new FileInputStream(f); BufferedInputStream bis = new BufferedInputStream(is); ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); int c = 0; while ((c = bis.read(buf, 0, buf.length)) > 0) { oos.write(buf, 0, c); oos.flush(); // buf=new byte[8192]; } oos.close(); //socket.shutdownOutput(); // client.shutdownOutput(); System.out.println("stop"); // client.shutdownOutput(); ois.close(); // Thread.sleep(500); is.close(); bis.close(); socket.close(); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE: here filePath represents the path of the file where it exists on the server. The client who is connecting to the server provides this path. I am managing this through sockets and I am successfully receiving this path. 3) FileReceiverThread is responsible for receiving the data from the server and constructing file from this buffer data. public class FileReceiveThread extends Thread { private String fileStorePath; private String sourceFile; private Socket socket = null; public FileReceiveThread(String ip, int port, String fileStorePath, String sourceFile) { this.fileStorePath = fileStorePath; this.sourceFile = sourceFile; try { socket = new Socket(ip, port); System.out.println("receive file thread " + socket.isConnected()); } catch (IOException ex) { ex.printStackTrace(); } } @Override public void run() { try { ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); oos.writeObject(sourceFile); oos.flush(); // oos.close(); File f = new File(fileStorePath); OutputStream os = new FileOutputStream(f); BufferedOutputStream bos = new BufferedOutputStream(os); byte[] buf = new byte[8192]; int c = 0; //************ NOTE ObjectInputStream ois = new ObjectInputStream( socket.getInputStream()); while ((c = ois.read(buf, 0, buf.length)) > 0) { // ois.read(buf); bos.write(buf, 0, c); bos.flush(); // buf = new byte[8192]; } ois.close(); oos.close(); // os.close(); bos.close(); socket.close(); //Thread.sleep(500); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE : Now the problem that I am facing is at the first time when the file is requested the outcome of the program is same as my expectation. I am able to transmit any size of file at first time. Now when the second file is requested (e.g. I have sent file a,b,c,d to the user and user has received file a successfully and now he is requesting file b) the program faces deadlock at this situation. It is waiting for socket's input stream. I put breakpoint and tried to debug it but it is not going in FileThread's run method second time. I could not find out the mistake here. Basically I am making a LAN Messenger which works on LAN. I am using SWT as UI framework.

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  • Is there an alternative to javascript for the web that can do multi-threading and synchronous execution?

    - by rambodash
    I would like to program web applications as I do with desktop programming languages, where the code is synchronously executed and browser doesn't freeze when doing loops. Yes I know there are workarounds using callbacks and setTimeout, but they are all workarounds after all and they don't give the same flexibility when programming in the orthodox way I've been looking at Dart as a possibilty, but I can't seem to find where it says it can do either of these. The same with haxe, emscript, and the hundreds of other converters that try to circumvent javascript. In the end it gets converted to Javascript so you ultimately have to be conscious about asynchronous/multi threading.

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  • Project development without experience

    - by Raven13
    I'm a web developer who is part of a three-man team that has been tasked with a rather large and complex development project. Other than some direction and impetus from management, we're pretty much on our own to develop the new website. None of us have any project management experience nor do my two coworkers seem like they would be interested in taking on that role, so I feel like it's up to me to implement some kind of structure to the development process in order to avoid issues down the road. My question is: what can I do as a developer without project managment experience to ensure that our project gets developed successfully and avoid the pitfalls of developing a project without a plan?

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  • Automatically analyze excel files

    - by dole doug
    I have to replicate a manual generation of a large number of excel files. I started to manually track the relations between cells ( files, formulas, etc). I also had a talk with the person which generates those files. For now I have a general understanding about how the excel files are generated, but "devil is in the details". I assume that I can write a script which will generate the hierarchy between cells and files, but this might require the same effort as manually noticing the relations. Also, I'm afraid that I'm not too experienced and my app is more prone to error approach than a manual analyze. How to handle this problem? Do you know about an open source project which analyze the excel files in a recursive mode following the formulas ?

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  • What is the oldest living piece of unaltered production code? [closed]

    - by user1598390
    It's come to my mind that parts of the code in, say, Unix, has maybe passed unaltered from one version or flavor into another. Maybe some pieces of the source code of the ls command is the same, unaltered, than was written years ago. Have any of you read or learn about this ? What would be the oldest living piece of unaltered production code still running, passing from version through version of a program or system ? Will the code we write outlive us for decades ?

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  • moore's law and quadratic algorithm

    - by damon
    I was going thru a video (from coursera - by sedgewick) in which he argues that you cannot sustain Moore's law using a quadratic algorithm.He elaborates like this In year 197* you build a computer of power X ,and need to count N objects.This takes M days According to Moore's law,you have a computer of power 2X after 1.5 years.But now you have 2N objects to count. If you use a quadratic algorithm, In year 197*+1.5 ,it takes (4M)/2 = 2M days 4M because the algorithm is quadratic,and division by 2 because of doubling computer power. I find this hard to understand.I tried to work thru this as below To count N objects using comp=X , it takes M days. -> N/X = M After 1.5 yrs ,you need to count 2N objects using comp=2X -> 2N/(2X) -> N/X -> M days where do I go wrong? can someone please help me understand?

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  • Web to Print system - which client side technology should I use

    - by mr null
    I'm getting started to develop Web to Print system. My main concern is which client-side techology should I use: jQuery/CSS Flex/ActionScript or something else? For now, idea is that user/customer choose Product eg: Business card Attributes: Dimensions,Paper type, ... etc Template or blank Adjust product (editor) Preview & order Output should be PDF 300dpi. My main issue is: adding/adjusting text in editor. (font size, font family...). Because application should be cross browser. And I think that 10px Arial can't be the same in Firefox 5 and IE 8. It must be pixel perfect in every browser. If somebody order $100 of business cards, and text is different that he/she saw when ordering - that is a big problem. So, Flash platform should be the answer. But, as I see it's dying technology, 2012 is here - HTML5 is replacing Flash rapidly. I hope that you understand me, so every guideline or few smart words would be very appreciating.

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  • Comunicate NodeJS and PHP

    - by Zenth
    i need ideas to solve this: I have a entire website in PHP (5.2) in a PHP "shared server", only i can use apache+PHP, CGI & NodeJS, no memcached, redis or another software. And i need to comunicate the PHP and the NodeJS Script. My first approach is using socket connection, creating in NodeJS a socket listener and connect to it witch PHP, and then, send commands, whait for response, and close connection (and end PHP Script). To the other side, i can call PHP script via ¿httprequest? ¿or using sockets again? The problem of using sockets fron Node to PHP, i CANT leave PHP script runing with set_time_limit(0) because the fuc... server, need to "call" PHP for another way. The NodeJS and Apache + PHP are in the same machine, i need to make the code for the fast response time (sockets better than web-calls). Better ideas or other solutions? thanks!

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  • documentation of typescript code

    - by Max Beikirch
    my question is rather short: How do I document typescript code properly? I found out that for projects becoming bigger and bigger, it is important to look at a function and immediately know parameters, what it returns and side-effects etc. It is tiring to have just a bunch of comments before a function, most of the time these 'blocks' even look differently in style. What I am looking for is a documentation tool like javadoc or doxygen for typescript. Is there anything out there? Or is it possible to 'abuse' a documentation tool and get it to work with typescript?

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  • Does double-shifting as a PM affect your developer-productivity?

    - by Roopesh Shenoy
    Has it ever happened to you that you are a good developer but suddenly you need to lead a team or are responsible for some PM activities as well? Did you find that it affected your productivity? How did you handle it? I love my job, but I sometimes feel I was much happier as a programmer and the additional burden of being a Project Manager is currently affecting my productivity as a developer. What do you guys suggest as remedies to this? I do not have an alternative currently to quit from my job - basically because Im working for a startup that I co-founded.

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  • Does BizSpark preclude you from accepting funding elsewhere?

    - by Clay Shannon
    I am going to embark very soon on a software venture (have been a consultant and employee up until now). I see advantages in signing up for Microsoft's BizSpark. However, I wonder if doing so would preclude me from accepting funding from some equity-esque arrangements potentially available via crowdfunding. I know BizSpark's legal agreement probably spells this out, but it's about a gazillion pages long, so I'm hoping somebody here has existing knowledge of this so I don't have to spend a lot of time reading legalese.

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