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  • Manual memory allocation and purity

    - by Eonil
    Language like Haskell have concept of purity. In pure function, I can't mutate any state globally. Anyway Haskell fully abstracts memory management, so memory allocation is not a problem here. But if languages can handle memory directly like C++, it's very ambiguous to me. In these languages, memory allocation makes visible mutation. But if I treat making new object as impure action, actually, almost nothing can be pure. So purity concept becomes almost useless. How should I handle purity in languages have memory as visible global object?

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  • C++ compile time purity checks?

    - by anon
    Is it possible to specify compile time "purity" checks in C++? I.e.: this function does not read from anything other than it's arguments this function does not write to anything; it only returns the return value

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  • Please give the solution of the following programs in R Programming

    - by NEETHU
    Table below gives data concerning the performance of 28 national football league teams in 1976.It is suspected that the no. of yards gained rushing by opponents(x8) has an effect on the no. of games won by a team(y) (a)Fit a simple linear regression model relating games won by y to yards gained rushing by opponents x8. (b)Construct the analysis of variance table and test for significance of regression. (c)Find a 95% CI on the slope. (d)What percent of the total variability in y is explained by this model. (e)Find a 95% CI on the mean number of games won in opponents yards rushing is limited to 2000 yards. Team y x8 1 10 2205 2 11 2096 3 11 1847 4 13 1803 5 10 1457 6 11 1848 7 10 1564 8 11 1821 9 4 2577 10 2 2476 11 7 1984 12 10 1917 13 9 1761 14 9 1709 15 6 1901 16 5 2288 17 5 2072 18 5 2861 19 6 2411 20 4 2289 21 3 2203 22 3 2592 23 4 2053 24 10 1979 25 6 2048 26 8 1786 27 2 2876 28 0 2560 Suppose we would like to use the model developed in problem 1 to predict the no. of games a team will win if it can limit opponents yards rushing to 1800 yards. Find a point estimate of the no. of games won when x8=1800.Find a 905 prediction interval on the no. of games won. The purity of Oxygen produced by a fractionation process is thought to be percentage of Hydrocarbon in the main condenser of the processing unit .20 samples are shown below. Purity(%) Hydrocarbon(%) 86.91 1.02 89.85 1.11 90.28 1.43 86.34 1.11 92.58 1.01 87.33 0.95 86.29 1.11 91.86 0.87 95.61 1.43 89.86 1.02 96.73 1.46 99.42 1.55 98.66 1.55 96.07 1.55 93.65 1.4 87.31 1.15 95 1.01 96.85 0.99 85.2 0.95 90.56 0.98 (a)Fit a simple linear regression model to the data. (b)Test the hypothesis H0:ß=0 (c)Calculate R2 . (d)Find a 95% CI on the slope. (e)Find a 95% CI on the mean purity and the Hydrocarbon % is 1. Consider the Oxygen plant data in Problem3 and assume that purity and Hydrocarbon percentage are jointly normally distributed r.vs (a)What is the correlation between Oxygen purity and Hydrocarbon% (b)Test the hypothesis that ?=0. (c)Construct a 95% CI for ?.

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  • Databases and Beer

    - by Johnm
    It is a bit of a no-brainer: Include the word "beer" in a subject line of an e-mail or blog post title and you can be certain that it will be read. While there are times this practice might be a ploy to increase readership, it is not the case for this blog post. There is inspiration that can be drawn from other industries to which we, as database professionals, can apply in our industry. In this post I will highlight one of my favorite participants of the brewing industry. The Boston Beer Company started in the 1970s in Boston, Massachusetts. Others may be more familiar with this company through their Samuel Adams Boston Lager and other various seasonal beers. I am continually inspired by their commitment to mastery of the brewing process to which they evangelize frequently in their commercials. They also are continually in pursuit of pushing the boundaries of beer as we know it while working within traditional constraints. A recent example of this is their collaboration with Weihenstephan Brewery of Munich, Germany to produce the soon to be released Infinium beer. This beer, while brewed as an ale, is touted as something closer to something like Champaign - all while complying with the Reinheitsgebot. The Reinheitsgebot is also known as the "German Beer Purity Law" which was originated in 1516. This law states that beer is to consist of water, barley, hops and yeast. That's it. Quite a limiting constraint indeed. and yet, The Boston Beer Company pushed forward. Much like the process of brewing, the discipline of database design and architecture is one that is continually in process and driven by the pursuit of mastery. While we do not have purity laws to constrain us, we have many other types: best practices, company policies, government regulations, security and budgets. Through our fellow comrades, we discuss the challenges and constraints in which we operate. We boil down the principles and theories that define our profession. We reassemble these into something that is complementary to the business needs that we must fulfill. As a result, it is not uncommon to see something amazingly innovative in a small business who is pushing the boundaries of their database well beyond its intended state. It is equally common to see innovation in the use of features available in the more advanced features of databases that are found in large businesses. The tag line for The Boston Beer Company is: "Take Pride In Your Beer.", I would like to offer an alternative and say "Take Pride In Your Database." So, As you pour your next Boston Lager into a frosted glass, consider those who spend their lives mastering the craft of brewing and strive to interject their spirit into everything that you do as a database professional. Cheers!

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  • Haskell vs Erlang for web services

    - by Zachary K
    I am looking to start an experimental project using a functional language and am trying to decide beween Erlang and Haskell, and both have some points that I really like. I like Haskell's strong type system and purity. I have a feeling it will make it easier to write really reliable code. And I think that the power of haskell will make some of what I want to do much easier. On the minus side I get the feeling that some of the Frameworks for doing web stuff on Haskell such as Yesod are not as advanced as their Erlang counter parts. I rather like the Erlang approach to threads and to fault tollerence. I have a feeling that the scalability of Erlang could be a major plus. Which leeds to to my question, what has people's exerience been in implementing web application backends in both Haskell and Erlang. Are there packages for Haskell to provide some of the lightweight threads and actors that one has in Erlang?

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  • How do you enhance your websites speed without compromising the design and access?

    - by Thorn007
    How do you enhance your websites load speed without killing the design and accessibility? File compression, CDN, Gzip? What are the best tools for doing so? For example, Google has optimized their site without compromising the design. Also, many website can kill the purity of their images with compression. Is there a way, more or lest best practice, to increase speed without compromising the design and accessibility? Note: sorry for being so vague but I don't know how else to phrase this question.

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  • What's cool about Lisp nowadays? [closed]

    - by Kos
    Possible Duplicates: Why is Lisp useful? Is LISP still useful in today's world? Which version is most used? First of all, let me clarify: I'm aware of Lisp's place in history, as well as in education. I'm asking about its place in practical application, as of 2011. The question is: What features of Lisp make it the preferred choice for projects today? It's widely used in various AI areas as far as I know, and probably also elsewhere. I can imagine projects choosing, for instance... Python because of its concise, readable syntax and it being dynamic, Haskell for being pure functional with a powerful type system, Matlab/Octave for the focus on numerics and big standard libraries, Etc. When should I consider Lisp the proper language for a given problem? What language features make it the preferred choice then? Is its "purity and generality" an advantage which makes it a better choice for some subset of projects than the modern languages? edit- On your demand, a little rephrase (or simply a tl;dr) to make this more specific: a) What problems are solvable with Lisp much more easily than with more common, modern languages like Python or C# (or even F# or Scala)? b) What language features specific for Lisp make it the best choice for those problems?

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  • Dependency Injection and method signatures

    - by sunwukung
    I've been using YADIF (yet another dependency injection framework) in a PHP/Zend app I'm working on to handle dependencies. This has achieved some notable benefits in terms of testing and decoupling classes. However,one thing that strikes me is that despite the sleight of hand performed when using this technique, the method names impart a degree of coupling. Probably not the best example -but these methods are distinct from ... say the PEAR Mailer. The method names themselves are a (subtle) form of coupling //example public function __construct($dic){ $this->dic = $dic; } public function example(){ //this line in itself indicates the YADIF origin of the DIC $Mail= $dic->getComponent('mail'); $Mail->setBodyText($body); $Mail->setFrom($from); $Mail->setSubject($subject); } I could write a series of proxies/wrappers to hide these methods and thus promote decoupling from , but this seems a bit excessive. You have to balance purity with pragmatism... How far would you go to hide the dependencies in your classes?

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  • Google Cloud DNS and DNSSEC?

    - by Joe Burnett
    Since Google Cloud DNS does not currently support the record types for DNSSEC, is there any way to begin implementation of DNSSEC using TXT records? If I were using Google Cloud DNS, which I am, and they currently only support record types which include SOA, A, AAAA, CNAME, MX, NS, SPF, SRV, PTR and TXT: am I able to do it while constricted to these record types? Or do I have to wait until support is hard-coded into the service? I am just wondering because I would really like to ensure absolute integrity for my company so that I only convey realness in it's purity. =D

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  • Dadaism and Agility

    - by alexhildyard
    We all have our little bugbears, and something that has given me particular pause over the years is the place of Agility in the software development life cycle. While I have seen it used successfully on both small and Enterprise-level projects, I have also seen many instances in which long-standing technical debt has also originated under its watch. Ironically the problem in such cases seems to me not that the practitioners in question have failed to follow due process (Test, Develop, Refactor -- a common "what" of Agile), but basically that they have missed the point (the "why" of Agile). It's probably a sign of my age that I'm much more interested in the "why" than the "what", since I feel that the latter falls out naturally from the former, but that this is not a reciprocal relationship.Consider Dadaism, precursor to the Surrealist movement in the early part of the twentieth century. Anyone could stand up and proclaim he or she was Dada; anyone could write cut-ups, or pull words out a hat, or produce gibberish on duelling typewriters under the inspiration of Dada. And all that took place at such performances was a manifestation of Dada, and all the artefacts that resulted were also Dada. Hence one commentator's engimatic observation that 'when one speaks of Dada, then one speaks of Dada. But when one does not speak of Dada, one still speaks of Dada.'What is Dada? Literally, Dada is what you say it is. But that's also missing the point. Dada is about erecting a framework within which utterances like this are valid; Dada is about preparing a stage for itself. Dadaism exemplifies the purity of a process-driven ideology -- in fact an ideology that is almost pure process, with nothing extraneous in the way of formal method, and while perhaps Agile delivery should not embrace the liberties of Dadaism too literally, some of the similarities nevertheless are salutary.Agile -- like Dada -- is an attitude; it is about *being* agile; it is not really about doing a specific set of things that are somehow *part* of being Agile. It is an abstract base rather than an implementation, a characteristic rather than a factor. It is the pragmatic response to the need for change in the face of partial information, ephemeral requirements and a healthy dose of systematic uncertainty. In practice this will usually mean repeatedly making the smallest useful changes to a system, recognising that systems evolve, and that all change carries risk. It will usually mean that instead of investing effort in future-proofing a system against a known technology roadmap, one instead invests one's energies in the daily repetition and incremental development of processes best designed to accommodate change quickly. But though it may mean these things in practice, it isn't actually *about* either of these things; it's about the mindset, the attitude that conceives of such responses as sensible solutions given the larger and ultimately unclassifiable thing that constitutes the development lifecycle of a specific project.

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  • Table sorting & pagination with jQuery and Razor in ASP.NET MVC

    - by hajan
    Introduction jQuery enjoys living inside pages which are built on top of ASP.NET MVC Framework. The ASP.NET MVC is a place where things are organized very well and it is quite hard to make them dirty, especially because the pattern enforces you on purity (you can still make it dirty if you want so ;) ). We all know how easy is to build a HTML table with a header row, footer row and table rows showing some data. With ASP.NET MVC we can do this pretty easy, but, the result will be pure HTML table which only shows data, but does not includes sorting, pagination or some other advanced features that we were used to have in the ASP.NET WebForms GridView. Ok, there is the WebGrid MVC Helper, but what if we want to make something from pure table in our own clean style? In one of my recent projects, I’ve been using the jQuery tablesorter and tablesorter.pager plugins that go along. You don’t need to know jQuery to make this work… You need to know little CSS to create nice design for your table, but of course you can use mine from the demo… So, what you will see in this blog is how to attach this plugin to your pure html table and a div for pagination and make your table with advanced sorting and pagination features.   Demo Project Resources The resources I’m using for this demo project are shown in the following solution explorer window print screen: Content/images – folder that contains all the up/down arrow images, pagination buttons etc. You can freely replace them with your own, but keep the names the same if you don’t want to change anything in the CSS we will built later. Content/Site.css – The main css theme, where we will add the theme for our table too Controllers/HomeController.cs – The controller I’m using for this project Models/Person.cs – For this demo, I’m using Person.cs class Scripts – jquery-1.4.4.min.js, jquery.tablesorter.js, jquery.tablesorter.pager.js – required script to make the magic happens Views/Home/Index.cshtml – Index view (razor view engine) the other items are not important for the demo. ASP.NET MVC 1. Model In this demo I use only one Person class which defines Person entity with several properties. You can use your own model, maybe one which will access data from database or any other resource. Person.cs public class Person {     public string Name { get; set; }     public string Surname { get; set; }     public string Email { get; set; }     public int? Phone { get; set; }     public DateTime? DateAdded { get; set; }     public int? Age { get; set; }     public Person(string name, string surname, string email,         int? phone, DateTime? dateadded, int? age)     {         Name = name;         Surname = surname;         Email = email;         Phone = phone;         DateAdded = dateadded;         Age = age;     } } 2. View In our example, we have only one Index.chtml page where Razor View engine is used. Razor view engine is my favorite for ASP.NET MVC because it’s very intuitive, fluid and keeps your code clean. 3. Controller Since this is simple example with one page, we use one HomeController.cs where we have two methods, one of ActionResult type (Index) and another GetPeople() used to create and return list of people. HomeController.cs public class HomeController : Controller {     //     // GET: /Home/     public ActionResult Index()     {         ViewBag.People = GetPeople();         return View();     }     public List<Person> GetPeople()     {         List<Person> listPeople = new List<Person>();                  listPeople.Add(new Person("Hajan", "Selmani", "[email protected]", 070070070,DateTime.Now, 25));                     listPeople.Add(new Person("Straight", "Dean", "[email protected]", 123456789, DateTime.Now.AddDays(-5), 35));         listPeople.Add(new Person("Karsen", "Livia", "[email protected]", 46874651, DateTime.Now.AddDays(-2), 31));         listPeople.Add(new Person("Ringer", "Anne", "[email protected]", null, DateTime.Now, null));         listPeople.Add(new Person("O'Leary", "Michael", "[email protected]", 32424344, DateTime.Now, 44));         listPeople.Add(new Person("Gringlesby", "Anne", "[email protected]", null, DateTime.Now.AddDays(-9), 18));         listPeople.Add(new Person("Locksley", "Stearns", "[email protected]", 2135345, DateTime.Now, null));         listPeople.Add(new Person("DeFrance", "Michel", "[email protected]", 235325352, DateTime.Now.AddDays(-18), null));         listPeople.Add(new Person("White", "Johnson", null, null, DateTime.Now.AddDays(-22), 55));         listPeople.Add(new Person("Panteley", "Sylvia", null, 23233223, DateTime.Now.AddDays(-1), 32));         listPeople.Add(new Person("Blotchet-Halls", "Reginald", null, 323243423, DateTime.Now, 26));         listPeople.Add(new Person("Merr", "South", "[email protected]", 3232442, DateTime.Now.AddDays(-5), 85));         listPeople.Add(new Person("MacFeather", "Stearns", "[email protected]", null, DateTime.Now, null));         return listPeople;     } }   TABLE CSS/HTML DESIGN Now, lets start with the implementation. First of all, lets create the table structure and the main CSS. 1. HTML Structure @{     Layout = null;     } <!DOCTYPE html> <html> <head>     <title>ASP.NET & jQuery</title>     <!-- referencing styles, scripts and writing custom js scripts will go here --> </head> <body>     <div>         <table class="tablesorter">             <thead>                 <tr>                     <th> value </th>                 </tr>             </thead>             <tbody>                 <tr>                     <td>value</td>                 </tr>             </tbody>             <tfoot>                 <tr>                     <th> value </th>                 </tr>             </tfoot>         </table>         <div id="pager">                      </div>     </div> </body> </html> So, this is the main structure you need to create for each of your tables where you want to apply the functionality we will create. Of course the scripts are referenced once ;). As you see, our table has class tablesorter and also we have a div with id pager. In the next steps we will use both these to create the needed functionalities. The complete Index.cshtml coded to get the data from controller and display in the page is: <body>     <div>         <table class="tablesorter">             <thead>                 <tr>                     <th>Name</th>                     <th>Surname</th>                     <th>Email</th>                     <th>Phone</th>                     <th>Date Added</th>                 </tr>             </thead>             <tbody>                 @{                     foreach (var p in ViewBag.People)                     {                                 <tr>                         <td>@p.Name</td>                         <td>@p.Surname</td>                         <td>@p.Email</td>                         <td>@p.Phone</td>                         <td>@p.DateAdded</td>                     </tr>                     }                 }             </tbody>             <tfoot>                 <tr>                     <th>Name</th>                     <th>Surname</th>                     <th>Email</th>                     <th>Phone</th>                     <th>Date Added</th>                 </tr>             </tfoot>         </table>         <div id="pager" style="position: none;">             <form>             <img src="@Url.Content("~/Content/images/first.png")" class="first" />             <img src="@Url.Content("~/Content/images/prev.png")" class="prev" />             <input type="text" class="pagedisplay" />             <img src="@Url.Content("~/Content/images/next.png")" class="next" />             <img src="@Url.Content("~/Content/images/last.png")" class="last" />             <select class="pagesize">                 <option selected="selected" value="5">5</option>                 <option value="10">10</option>                 <option value="20">20</option>                 <option value="30">30</option>                 <option value="40">40</option>             </select>             </form>         </div>     </div> </body> So, mainly the structure is the same. I have added @Razor code to create table with data retrieved from the ViewBag.People which has been filled with data in the home controller. 2. CSS Design The CSS code I’ve created is: /* DEMO TABLE */ body {     font-size: 75%;     font-family: Verdana, Tahoma, Arial, "Helvetica Neue", Helvetica, Sans-Serif;     color: #232323;     background-color: #fff; } table { border-spacing:0; border:1px solid gray;} table.tablesorter thead tr .header {     background-image: url(images/bg.png);     background-repeat: no-repeat;     background-position: center right;     cursor: pointer; } table.tablesorter tbody td {     color: #3D3D3D;     padding: 4px;     background-color: #FFF;     vertical-align: top; } table.tablesorter tbody tr.odd td {     background-color:#F0F0F6; } table.tablesorter thead tr .headerSortUp {     background-image: url(images/asc.png); } table.tablesorter thead tr .headerSortDown {     background-image: url(images/desc.png); } table th { width:150px;            border:1px outset gray;            background-color:#3C78B5;            color:White;            cursor:pointer; } table thead th:hover { background-color:Yellow; color:Black;} table td { width:150px; border:1px solid gray;} PAGINATION AND SORTING Now, when everything is ready and we have the data, lets make pagination and sorting functionalities 1. jQuery Scripts referencing <link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" /> <script src="@Url.Content("~/Scripts/jquery-1.4.4.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.tablesorter.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.tablesorter.pager.js")" type="text/javascript"></script> 2. jQuery Sorting and Pagination script   <script type="text/javascript">     $(function () {         $("table.tablesorter").tablesorter({ widthFixed: true, sortList: [[0, 0]] })         .tablesorterPager({ container: $("#pager"), size: $(".pagesize option:selected").val() });     }); </script> So, with only two lines of code, I’m using both tablesorter and tablesorterPager plugins, giving some options to both these. Options added: tablesorter - widthFixed: true – gives fixed width of the columns tablesorter - sortList[[0,0]] – An array of instructions for per-column sorting and direction in the format: [[columnIndex, sortDirection], ... ] where columnIndex is a zero-based index for your columns left-to-right and sortDirection is 0 for Ascending and 1 for Descending. A valid argument that sorts ascending first by column 1 and then column 2 looks like: [[0,0],[1,0]] (source: http://tablesorter.com/docs/) tablesorterPager – container: $(“#pager”) – tells the pager container, the div with id pager in our case. tablesorterPager – size: the default size of each page, where I get the default value selected, so if you put selected to any other of the options in your select list, you will have this number of rows as default per page for the table too. END RESULTS 1. Table once the page is loaded (default results per page is 5 and is automatically sorted by 1st column as sortList is specified) 2. Sorted by Phone Descending 3. Changed pagination to 10 items per page 4. Sorted by Phone and Name (use SHIFT to sort on multiple columns) 5. Sorted by Date Added 6. Page 3, 5 items per page   ADDITIONAL ENHANCEMENTS We can do additional enhancements to the table. We can make search for each column. I will cover this in one of my next blogs. Stay tuned. DEMO PROJECT You can download demo project source code from HERE.CONCLUSION Once you finish with the demo, run your page and open the source code. You will be amazed of the purity of your code.Working with pagination in client side can be very useful. One of the benefits is performance, but if you have thousands of rows in your tables, you will get opposite result when talking about performance. Hence, sometimes it is nice idea to make pagination on back-end. So, the compromise between both approaches would be best to combine both of them. I use at most up to 500 rows on client-side and once the user reach the last page, we can trigger ajax postback which can get the next 500 rows using server-side pagination of the same data. I would like to recommend the following blog post http://weblogs.asp.net/gunnarpeipman/archive/2010/09/14/returning-paged-results-from-repositories-using-pagedresult-lt-t-gt.aspx, which will help you understand how to return page results from repository. I hope this was helpful post for you. Wait for my next posts ;). Please do let me know your feedback. Best Regards, Hajan

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  • To (monkey)patch or not to (monkey)patch, that is the question

    - by gsakkis
    I was talking to a colleague about one rather unexpected/undesired behavior of some package we use. Although there is an easy fix (or at least workaround) on our end without any apparent side effect, he strongly suggested extending the relevant code by hard patching it and posting the patch upstream, hopefully to be accepted at some point in the future. In fact we maintain patches against specific versions of several packages that are applied automatically on each new build. The main argument is that this is the right thing to do, as opposed to an "ugly" workaround or a fragile monkey patch. On the other hand, I favor practicality over purity and my general rule of thumb is that "no patch" "monkey patch" "hard patch", at least for anything other than a (critical) bug fix. So I'm wondering if there is a consensus on when it's better to (hard) patch, monkey patch or just try to work around a third party package that doesn't do exactly what one would like. Does it have mainly to do with the reason for the patch (e.g. fixing a bug, modifying behavior, adding missing feature), the given package (size, complexity, maturity, developer responsiveness), something else or there are no general rules and one should decide on a case-by-case basis ?

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  • How can I round money values to the nearest $5.00 interval?

    - by Frank Developer
    I have an Informix-SQL based Pawnshop app which calculates an estimate of how much money should be loaned to a customer, based on the weight and purity of gold. The minimum the pawnshop lends is $5.00. The pawnshop employee will typically lend amounts which either ends with a 5 or 0. examples: 10, 15, 20, 100, 110, 125, etc. They do this so as to not run into shortage problems with $1.00 bills. So, if for example my system calculates the loan should be: $12.49, then round it to $10, $12.50 to $15.00, $13.00 to $15.00, $17.50 to $20.00, and so on!..The employee can always override the rounded amount if necessary. Is it possible to accomplish this within the instructions section of a perform screen or would I have to write a cfunc and call it from within perform?.. Are there any C library functions which perform interval rounding of money values?.. On another note, I think the U.S. Government should discontinue the use of pennies so that businesses can round amounts to the nearest nickel, it would save so much time and weight in our pockets!

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  • Ruby and duck typing: design by contract impossible?

    - by davetron5000
    Method signature in Java: public List<String> getFilesIn(List<File> directories) similar one in ruby def get_files_in(directories) In the case of Java, the type system gives me information about what the method expects and delivers. In Ruby's case, I have no clue what I'm supposed to pass in, or what I'll expect to receive. In Java, the object must formally implement the interface. In Ruby, the object being passed in must respond to whatever methods are called in the method defined here. This seems highly problematic: Even with 100% accurate, up-to-date documentation, the Ruby code has to essentially expose its implementation, breaking encapsulation. "OO purity" aside, this would seem to be a maintenance nightmare. The Ruby code gives me no clue what's being returned; I would have to essentially experiment, or read the code to find out what methods the returned object would respond to. Not looking to debate static typing vs duck typing, but looking to understand how you maintain a production system where you have almost no ability to design by contract. Update No one has really addressed the exposure of a method's internal implementation via documentation that this approach requires. Since there are no interfaces, if I'm not expecting a particular type, don't I have to itemize every method I might call so that the caller knows what can be passed in? Or is this just an edge case that doesn't really come up?

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  • Why doesn't C# do "simple" type inference on generics?

    - by Ken Birman
    Just curious: sure, we all know that the general case of type inference for generics is undecidable. And so C# won't do any kind of subtyping at all: if Foo<T> is a generic, Foo<int> isn't a subtype of Foo<T>, or Foo<Object> or of anything else you might cook up. And sure, we all hack around this with ugly interface or abstract class definitions. But... if you can't beat the general problem, why not just limit the solution to cases that are easy. For example, in my list above, it is OBVIOUS that Foo<int> is a subtype of Foo<T> and it would be trivial to check. Same for checking against Foo<Object>. So is there some other deep horror that would creep forth from the abyss if they were to just say, aw shucks, we'll do what we can? Or is this just some sort of religious purity on the part of the language guys at Microsoft?

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  • Can anyone explain me the source code of python "import this"?

    - by byterussian
    If you open a Python interpreter, and type "import this", as you know, it prints: The Zen of Python, by Tim Peters Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than *right* now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those! In the python source(Lib/this.py) this text is generated by a curios piece of code: s = """Gur Mra bs Clguba, ol Gvz Crgref Ornhgvshy vf orggre guna htyl. Rkcyvpvg vf orggre guna vzcyvpvg. Fvzcyr vf orggre guna pbzcyrk. Pbzcyrk vf orggre guna pbzcyvpngrq. Syng vf orggre guna arfgrq. Fcnefr vf orggre guna qrafr. Ernqnovyvgl pbhagf. Fcrpvny pnfrf nera'g fcrpvny rabhtu gb oernx gur ehyrf. Nygubhtu cenpgvpnyvgl orngf chevgl. Reebef fubhyq arire cnff fvyragyl. Hayrff rkcyvpvgyl fvyraprq. Va gur snpr bs nzovthvgl, ershfr gur grzcgngvba gb thrff. Gurer fubhyq or bar-- naq cersrenoyl bayl bar --boivbhf jnl gb qb vg. Nygubhtu gung jnl znl abg or boivbhf ng svefg hayrff lbh'er Qhgpu. Abj vf orggre guna arire. Nygubhtu arire vf bsgra orggre guna *evtug* abj. Vs gur vzcyrzragngvba vf uneq gb rkcynva, vg'f n onq vqrn. Vs gur vzcyrzragngvba vf rnfl gb rkcynva, vg znl or n tbbq vqrn. Anzrfcnprf ner bar ubaxvat terng vqrn -- yrg'f qb zber bs gubfr!""" d = {} for c in (65, 97): for i in range(26): d[chr(i+c)] = chr((i+13) % 26 + c) print "".join([d.get(c, c) for c in s])

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