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• When is type testing OK?

  - by svidgen

  Assuming a language with some inherent type safety (e.g., not JavaScript): Given a method that accepts a SuperType, we know that in most cases wherein we might be tempted to perform type testing to pick an action: public void DoSomethingTo(SuperType o) { if (o isa SubTypeA) { o.doSomethingA() } else { o.doSomethingB(); } } We should usually, if not always, create a single, overridable method on the SuperType and do this: public void DoSomethingTo(SuperType o) { o.doSomething(); } ... wherein each subtype is given its own doSomething() implementation. The rest of our application can then be appropriately ignorant of whether any given SuperType is really a SubTypeA or a SubTypeB. Wonderful. But, we're still given is a-like operations in most, if not all, type-safe languages. And that seems suggests a potential need for explicit type testing. So, in what situations, if any, should we or must we perform explicit type testing? Forgive my absent mindedness or lack of creativity. I know I've done it before; but, it was honestly so long ago I can't remember if what I did was good! And in recent memory, I don't think I've encountered a need to test types outside my cowboy JavaScript.

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• Is there an established convention for separating Windows file names in a string?

  - by Heinzi

  I have a function which needs to output a string containing a list of file paths. I can choose the separation character but I cannot change the data type (e.g. I cannot return a List<string> or something like that). Wanting to use some well-established convention, my first intuition was to use the semicolon, similar to what Windows's PATH and Java's CLASSPATH (on Windows) environment variables do: C:\somedir\somefile.txt;C:\someotherdir\someotherfile.txt However, I was surprised to notice that ; is a valid character in an NTFS file name. So, is the established best practice to just ignore this fact (i.e. "no sane person should use ; in a file name and if they do, it's their own fault") or is there some other established character for separating Windows paths or files? (The pipe (|) might be a good choice, but I have not seen it used anywhere yet for this purpose.)

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• Learning curve regarding the transition from Windows to Linux from a Java developer perspective [closed]

  - by Geek

  I am a Java developer who has worked on windows platform all through . Now I have shifted job and my new job requires me to do the development work in Red Hat Linux environment . The IDE they use is JDeveloper . I do not have any prior experience in Linux and JDeveloper . So what suggestion would you guys give me so that I can have a smooth and incremental transition from Windows to Linux ? I do not want to short circuit my learning curve . I want to learn it the correct way . Any suggestions regrading any good books,links etc that will help to get started is welcome .

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• Is it wise to store a big lump of json on a database row

  - by Ieyasu Sawada

  I have this project which stores product details from amazon into the database. Just to give you an idea on how big it is: [{"title":"Genetic Engineering (Opposing Viewpoints)","short_title":"Genetic Engineering ...","brand":"","condition":"","sales_rank":"7171426","binding":"Book","item_detail_url":"http://localhost/wordpress/product/?asin=0737705124","node_list":"Books > Science & Math > Biological Sciences > Biotechnology","node_category":"Books","subcat":"","model_number":"","item_url":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/ecom_redirector.php?id=128","details_url":"http://localhost/wordpress/product/?asin=0737705124","large_image":"http://localhost/wordpress/wp-content/plugins/ecom/img/large-notfound.png","medium_image":"http://localhost/wordpress/wp-content/plugins/ecom/img/medium-notfound.png","small_image":"http://localhost/wordpress/wp-content/plugins/ecom/img/small-notfound.png","thumbnail_image":"http://localhost/wordpress/wp-content/plugins/ecom/img/thumbnail-notfound.png","tiny_img":"http://localhost/wordpress/wp-content/plugins/ecom/img/tiny-notfound.png","swatch_img":"http://localhost/wordpress/wp-content/plugins/ecom/img/swatch-notfound.png","total_images":"6","amount":"33.70","currency":"$","long_currency":"USD","price":"$33.70","price_type":"List Price","show_price_type":"0","stars_url":"","product_review":"","rating":"","yellow_star_class":"","white_star_class":"","rating_text":" of 5","reviews_url":"","review_label":"","reviews_label":"Read all ","review_count":"","create_review_url":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/ecom_redirector.php?id=132","create_review_label":"Write a review","buy_url":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/ecom_redirector.php?id=19186","add_to_cart_action":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/add_to_cart.php","asin":"0737705124","status":"Only 7 left in stock.","snippet_condition":"in_stock","status_class":"ninstck","customer_images":["http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/51M2vvFvs2BL.jpg","http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/31FIM-YIUrL.jpg","http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/51M2vvFvs2BL.jpg","http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/51M2vvFvs2BL.jpg"],"disclaimer":"","item_attributes":[{"attr":"Author","value":"Greenhaven Press"},{"attr":"Binding","value":"Hardcover"},{"attr":"EAN","value":"9780737705126"},{"attr":"Edition","value":"1"},{"attr":"ISBN","value":"0737705124"},{"attr":"Label","value":"Greenhaven Press"},{"attr":"Manufacturer","value":"Greenhaven Press"},{"attr":"NumberOfItems","value":"1"},{"attr":"NumberOfPages","value":"224"},{"attr":"ProductGroup","value":"Book"},{"attr":"ProductTypeName","value":"ABIS_BOOK"},{"attr":"PublicationDate","value":"2000-06"},{"attr":"Publisher","value":"Greenhaven Press"},{"attr":"SKU","value":"G0737705124I2N00"},{"attr":"Studio","value":"Greenhaven Press"},{"attr":"Title","value":"Genetic Engineering (Opposing Viewpoints)"}],"customer_review_url":"http://localhost/wordpress/wp-content/ecom-customer-reviews/0737705124.html","flickr_results":["http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/5105560852_06c7d06f14_m.jpg"],"freebase_text":"No around the web data available yet","freebase_image":"http://localhost/wordpress/wp-content/plugins/ecom/img/freebase-notfound.jpg","ebay_related_items":[{"title":"Genetic Engineering (Introducing Issues With Opposing Viewpoints), , Good Book","image":"http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/140.jpg","url":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/ecom_redirector.php?id=12165","currency_id":"$","current_price":"26.2"},{"title":"Genetic Engineering Opposing Viewpoints by DAVID BENDER - 1964 Hardcover","image":"http://localhost/wordpress/wp-content/uploads/2013/10/ecom_images/140.jpg","url":"http://localhost/wordpress/wp-content/ecom-plugin-redirects/ecom_redirector.php?id=130","currency_id":"AUD","current_price":"11.99"}],"no_follow":"rel=\"nofollow\"","new_tab":"target=\"_blank\"","related_products":[],"super_saver_shipping":"","shipping_availability":"","total_offers":"7","added_to_cart":""}] So the structure for the table is: asin title details (the product details in json) Will the performance suffer if I have to store like 10,000 products? Is there any other way of doing this? I'm thinking of the following, but the current setup is really the most convenient one since I also have to use the data on the client side: store the product details in a file. So something like ASIN123.json store the product details in one big file. (I'm guessing it will be a drag to extract data from this file) store each of the fields in the details in its own table field Thanks in advance!

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• Why Mac OS X is referred to as the developer's OS? [closed]

  - by dbramhall

  Possible Duplicate: Why do programmers use or recommend Mac OS X? I have heard people referring to Mac OS X as the 'developer's operating system' and I was wondering why? I have been using Mac OS X for years but I only see Mac OS X as a developer's OS if the developer tools are installed, without them it's not really a developer's OS. Also, the Terminal is obviously a huge plus for developers but is this it?

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• ACORD LOMA 2010: Building Insurance Companies in the Clouds

  - by [email protected]

  Chuck Johnston, vice president of global strategy and alliances for Oracle Insurance, participated in a featured speaking session at ACORD LOMA 2010. He provides an update on his discussions with insurers at the show and after his presentation. Every year I always make a point of walking the show floor at the ACORD LOMA technology conference to visit with colleagues and competitors, and try to get a feel for which way the industry will move over the next 12 months. Insurers are looking for substance in cloud (computing), trying to mix business with pleasure (monetizing social networks), and expect differentiation through commodity (Software as a Service). The disconnect at this show is that most vendors are still struggling with creating a clear path from Facebook to customer intimacy, SaaS to core cost savings and clouds to ubiquitous presence. Vendors need to find new ways to help insurers find the real value in these potentially disruptive technologies by understanding the changes coming to the insurance business and how these new technologies impact the new insurance business. Oracle's approach to understanding the evolving insurance industry comes from a discussion with our customers in our Insurance CIO Council, where one of our customers suggested we buy an insurance company to really understand our customers. We have decided to do the next best thing and build our own model of an insurance company, Alamere Insurance, that uses the latest technologies to transform its own business. Alamere will never issue an actual policy, but it does give us a framework to consider the impacts of changes in the insurance landscape and how Oracle technology meets the challenge or needs to evolve to help our customers be successful. In preparing for my talk at the conference using Alamere as my organizing theme, I found myself reading actuarial memoranda on CSO table changes and articles on underwriting theory that really made me think about my customer's problems first and foremost, and then how Oracle technology can provide answers. As much as I prefer techno-thrillers and sci-fi novels to actuarial papers for plane reading, I got very excited about the idea of putting myself back in the customer shoes I haven't worn in a decade, and really looking at how Oracle can power the Adaptive Insurance Enterprise. Talking to customers and industry people after the session, the idea of Alamere seemed to excite people and I got a lot of suggestions as to what lines of business we should model and where we should focus first on technology uptake. One customer said to a colleague that Oracle's attempt to "share their pain" was unique among vendors. More about Alamere, and the Adaptive Insurance Enterprise next time. Chuck Johnston is vice president of global strategy and alliances for Oracle Insurance.

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• Why do I bother with RAID 10 ?

  - by GrumpyOldDBA

  Before I post anything I just want to clarify what I mean by RAID 10 , this is sets of mirrored pairs that have been striped as against a RAID 0 which has been mirrored. I've just had a disk failure in the data array for one of my dev servers, it's an eight disk raid 8, no real worries, replace disk and off we go - but no - the HP engineers told me from the diagnostics ( done to ensure I got the right replacement under warranty ) that not only had a disk failed but I'd lost all the data...(read more)

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• Top 5 Sites and Activities in San Francisco to Experience During Oracle OpenWorld

  - by kgee

  While Oracle OpenWorld may provide solutions and information on topics like how to simplify your IT, the importance of cloud, and what types of storage may satisfy your enterprise needs, who is going to tell you more about San Francisco? Here are some suggested sites and activities to experience after OpenWorld that aren’t too far from the Moscone Center. It is recommended to take a cab for the sake of time, but the 6 square miles that make up San Francisco will make for a quick trek to any of the following destinations: The Golden Gate BridgeAn image often associated with San Francisco, this bridge is one of the most impressive in the world. Take a walk across it, or view it from nearby Crissy Field, it is a sight that floors even the most veteran of San Franciscans. The Ferry BuildingLocated at the end of Market Street in the Embarcadero, the Ferry Building once served as a hub of water transport and trade. The building has a bay front view and an array of food choices and restaurants. It is easily accessible via the Muni, BART, trolley or by cab. It is a must-see in San Francisco, and not too far from the Moscone Center. Ride the Trolley to the CastroFor only $2, you can get go back in history for a moment on the Trolley. Take the F-line from the Embarcadero and ride it all the way to the Castro district. During the ride, you will get an overview of the landscape and cultures that are prevalent in San Francisco, but be wary that some areas may beg for an open mind more than others. Golden Gate ParkWhen you tire of the concrete jungle, the lucky part of being in San Francisco is that you can escape to a natural refuge, this park being one of the favorites. This park is known for its hiking trails, cultural attractions, monuments, lakes and gardens. It is one good reason to bring your sneakers to San Francisco, and is also a great place to picnic. Please be wary that it is easy to get lost, and it is advisable to bring a map (just in case) if you go. Haight AshburyFor a complete change of scenery, Haight Ashbury is known as one of the places hippies used to live and the location of "The Summer of Love." It is now a more affluent neighborhood with boutique shops and the occasional drum circle. While it may be perceived as grungy in certain spots, it is one of the most photographed places in San Francisco and an integral part of San Franciscan history.

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• Is Ubuntu workable as a laptop for an IT consultant?

  - by Eric Wilson

  I work as a consultant programmer, typically in large businesses. I use a Windows Laptop, and many of my colleagues use a Mac. My personal preference would be to run Ubuntu if I could have complete control over my development environment. But I will have occasional need for Microsoft specific products, especially IE. My colleagues that use a Mac often run Windows on a virtual machine for these situations. My question is: Is Ubuntu a workable solution for the laptop of an enterprise programmer? For example, is it as easy to run Windows on a VM on Ubuntu as it is on a Mac? Has anyone out there tried this? Is there any particular reason why Ubuntu would not serve as well as a Mac for development in this environment? Note that I am not doing .NET development, so I am typically dealing with Java that is going to be run on an Apache server and used by clients running Windows.

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• If Scheme is untyped, how can it have numbers and lists?

  - by Dokkat

  Scheme is said to be just an extension of the Untyped Lambda Calculus (correct me if I am wrong). If that is the case, how can it have Lists and Numbers? Those, to me, look like 2 base types. So I'd say Racket is actually an extension of the Simply Typed Lambda Calculus. No? Question: Is Scheme's type system actually based or more similar to Simply Typed or Untyped Lambda Calculus? In what ways does it differ from Untyped and or Simply Typed Lambda Calculus? (The same question is valid for "untyped" languages such as Python and JavaScript - all of which look like they have base types to me.)

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• Is there any practical use for the empty type in Common Lisp?

  - by Pedro Rodrigues

  The Common Lisp spec states that nil is the name of the empty type, but I've never found any situation in Common Lisp where I felt like the empty type was useful/necessary. Is it there just for completeness sake (and removing it wouldn't cause any harm to anyone)? Or is there really some practical use for the empty type in Common Lisp? If yes, then I would prefer an answer with code example. For example, in Haskell the empty type can be used when binding foreign data structures, to make sure that no one tries to create values of that type without using the data structure's foreign interface (although in this case, the type is not really empty).

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• Confusion related to sigwait in multiprocess system

  - by user34790

  I am having difficulty in understanding IPC in multiprocess system. I have this system where there are three child processes that send two types of signals to their process group. There are four types of signal handling processes responsible for a particular type of signal. There is this monitoring process which waits for both the signals and then processes accordingly. When I run this program for a while, the monitoring process doesn't seem to pick up the signal as well as the signal handling process. I could see in the log that the signal is only being generated but not handled at all. My code is given below #include <cstdlib> #include <iostream> #include <iomanip> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <unistd.h> #include <fcntl.h> #include <cstdio> #include <stdlib.h> #include <stdio.h> #include <pthread.h> using namespace std; double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } double getinterval() { srand(time(NULL)); int r = rand()%10 + 1; double s = (double)r/100; } int count; int count_1; int count_2; double time_1[10]; double time_2[10]; pid_t senders[1]; pid_t handlers[4]; pid_t reporter; void catcher(int sig) { printf("Signal catcher called for %d",sig); } int main(int argc, char *argv[]) { void signal_catcher_int(int); pid_t pid,w; int status; if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2 ,SIG_IGN) == SIG_ERR) { perror("2"); return 2; } if(signal(SIGINT,signal_catcher_int) == SIG_ERR) { perror("3"); return 2; } //Registering the signal handler for(int i=0; i<4; i++) { if((pid = fork()) == 0) { cout << i << endl; //struct sigaction sigact; sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); if(i%2 == 0) { if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR1); sigprocmask(SIG_BLOCK, &sigset, NULL); } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); } while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The caught signal is " << sig << endl; } } exit(0); } else { cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } //Registering the monitoring process if((pid = fork()) == 0) { sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); sigaddset(&sigset, SIGUSR1); sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The monitored signal is " << sig << endl; } else { cout << "error" << endl; } } } else { reporter = pid; } sleep(3); //Registering the signal generator for(int i=0; i<1; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } srand(time(0)); while(true) { volatile int signal_id = rand()%2 + 1; cout << "Generating the signal " << signal_id << endl; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); } else { killpg(getpgid(getpid()), SIGUSR2); } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { cout << "Registered the sender " << pid << endl; senders[i] = pid; } } while(w = wait(&status)) { cout << "Wait on PID " << w << endl; } } void signal_catcher_int(int the_sig) { //cout << "Handling the Ctrl C signal " << endl; for(int i=0; i<1; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<4; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); } Any suggestions? Here is a sample of the output as well In the beginning Registerd the handler 9544 Registerd the handler 9545 1 Registerd the handler 9546 Registerd the handler 9547 2 3 0 Registered the sender 9550 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 2 The caught signal is 12 The caught signal is 12 The monitored signal is 12 Generating the signal 2 Generating the signal 2 The caught signal is 12 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is 10 The monitored signal is 12 Generating the signal 1 Generating the signal 2 The caught signal is 12 Generating the signal 1 Generating the signal 2 10 The monitored signal is 10 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is GenThe caught signal is TheThe caught signal is 10 Generating the signal 2 Later on The monitored signal is GenThe monitored signal is 10 Generating the signal 1 Generating the signal 2 The caught signal is 10 The caught signal is 10 The caught signal is 10 The caught signal is 12 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 The caught signal is 12 The caught signal is 10 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 As you can see initially, the signal was generated and handled both by my signal handlers and monitoring processes. But later on the signal was generated a lot, but it was not quite processes in the same magnitude as before. Further I could see very less signal processing by the monitoring process Can anyone please provide some insights. What's going on?

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• A good interpreted language for a small embedded project

  - by Earlz

  I have an mbed which has a small ARM Cortex M3 on it. Basically, my effective resources for the project are ~25Kb of RAM and ~400Kb of Flash. For I/O I'll have a PS/2 keyboard, a VGA framebuffer(with character output), and an SD card for saving/loading programs(up to a couple of Mb maybe) The reason I ask this here is because I'm trying to figure out what programming language to implement on the thing. I'm looking for an interpreted language that's easy for me to implement, and won't break the bank on my resources. I also intend for this to be at least possible to write on th device itself, though the editor can be interpreted(yay bootstrapping) Anyway, I've looked at a few simple languages. Some nice candidates: Forth BASIC Scheme? Has anyone done something like this or know of any languages that can fit this bill or have comments about my three candidates so far?

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• NoSQL as file meta database

  - by fga

  I am trying to implement a virtual file system structure in front of an object storage (Openstack). For availability reasons we initially chose Cassandra, however while designing file system data model, it looked like a tree structure similar to a relational model. Here is the dilemma for availability and partition tolerance we need NoSQL, but our data model is relational. The intended file system must be able to handle filtered search based on date, name etc. as fast as possible. So what path should i take? Stick to relational with some indexing mechanism backed by 3 rd tools like Apache Solr or dig deeper into NoSQL and find a suitable model and database satisfying the model? P.S: Currently from NoSQL Cassandra or MongoDB are choices proposed by my colleagues.

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• Storing lots of large strings with frequent "appends" and few reads

  - by Thiago Moraes

  In my current project, I need to store a very long ASCII string to each instance of a given object. This string will receive an 2 appends per minute and will not be retrieved so frequently. The worst case scenario is a 5-10MB string. I'll have thousands of instances of my object and I'm worried that storing all those strings in the filesystem would not be optimal, but I can't think of a better solution. Can anyone suggest an alternative? Maybe a key-value store? In this case, which one? Any other thoughts?

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• What is a non commital approach to software analysis

  - by dsjbirch

  When I think about software analysis the first thing which comes to mind is SSADM and the UML. But, what I want is a high level view of the system before I commit to a programming paradigm. Where am I going wrong? How do I approach a problem in a high level and generic way before I commit to a paradigm? What are the diagrams/tools available to support me? Edit: Some examples of tools that appear to be what I'm after are... A block diagram - http://en.wikipedia.org/wiki/Block_diagram A data flow diagram - http://en.wikipedia.org/wiki/Data_flow_diagram

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• Which statically typed languages support intersection types for function return values?

  - by stakx

  Initial note: This question got closed after several edits because I lacked the proper terminology to state accurately what I was looking for. Sam Tobin-Hochstadt then posted a comment which made me recognise exactly what that was: programming languages that support intersection types for function return values. Now that the question has been re-opened, I've decided to improve it by rewriting it in a (hopefully) more precise manner. Therefore, some answers and comments below might no longer make sense because they refer to previous edits. (Please see the question's edit history in such cases.) Are there any popular statically & strongly typed programming languages (such as Haskell, generic Java, C#, F#, etc.) that support intersection types for function return values? If so, which, and how? (If I'm honest, I would really love to see someone demonstrate a way how to express intersection types in a mainstream language such as C# or Java.) I'll give a quick example of what intersection types might look like, using some pseudocode similar to C#: interface IX { … } interface IY { … } interface IB { … } class A : IX, IY { … } class B : IX, IY, IB { … } T fn() where T : IX, IY { return … ? new A() : new B(); } That is, the function fn returns an instance of some type T, of which the caller knows only that it implements interfaces IX and IY. (That is, unlike with generics, the caller doesn't get to choose the concrete type of T — the function does. From this I would suppose that T is in fact not a universal type, but an existential type.) P.S.: I'm aware that one could simply define a interface IXY : IX, IY and change the return type of fn to IXY. However, that is not really the same thing, because often you cannot bolt on an additional interface IXY to a previously defined type A which only implements IX and IY separately. Footnote: Some resources about intersection types: Wikipedia article for "Type system" has a subsection about intersection types. Report by Benjamin C. Pierce (1991), "Programming With Intersection Types, Union Types, and Polymorphism" David P. Cunningham (2005), "Intersection types in practice", which contains a case study about the Forsythe language, which is mentioned in the Wikipedia article. A Stack Overflow question, "Union types and intersection types" which got several good answers, among them this one which gives a pseudocode example of intersection types similar to mine above.

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• Are there programming languages that allow you to do set arithmetic on types?

  - by Will Brown

  Out of curiosity, are there languages that allow you to do set arithmetic on types to create new types? Something like: interface A { void a(); void b(); } interface B { void b(); void c(); } interface C = A & B; // has b() interface D = A | B; // has a(), b() and c() interface E = (A & B) ^ B; // has c() I know that in some languages these ideas can be expressed (i.e., Java has List<Comparable & Serializable> for the union of the interfaces) but I've never heard of a language that supports type arithmetic. Thanks!

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• Sun Fire servers 3D Demos

  - by ferhat

  Sun Fire X48003D Demo Sun Fire X4470 M23D Demo Sun Fire X4170 M23D Demo Sun Fire X2270 M23D Demo Visit Oracle Technology Network pages and product pages for more information on Sun Fire x86 servers.

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• Webcast: John Fowler Reveals The Next Step In Data Center Consolidation – June 27 At 10 AM PT

  - by Roxana Babiciu

  Completely integrated solutions are just better. But don't take our word for it - encourage your customers and prospects to join this live webcast featuring Oracle EVP John Fowler to find out why. Participants will learn how consolidating their existing data center to this new generation of solutions will simplify architectures, jump start application deployment and improve system performance - with easy self-service and private cloud capabilities.

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• Why doesn't Haskell have type-level lambda abstractions?

  - by Petr Pudlák

  Are there some theoretical reasons for that (like that the type checking or type inference would become undecidable), or practical reasons (too difficult to implement properly)? Currently, we can wrap things into newtype like newtype Pair a = Pair (a, a) and then have Pair :: * -> * but we cannot do something like ?(a:*). (a,a). (There are some languages that have them, for example, Scala does.)

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• New Oracle Database Performance and Tuning Specialization version available to all partners!

  - by Catalin Teodor

  Any partner working with the Oracle database should take advantage of the new Oracle Database Performance and Tuning specialization version. Have partners review the criteria and see what’s new in this specialization solution update. Partners should plan to take the new version as the Oracle Database 11g Performance Tuning specialization becomes non-qualifying as of August 1, 2015.

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• airplanes operating system and choice of programing language

  - by adhg

  I was wondring if anyone knows what is the operating system used in commercial airplanes (say Boeing or Airbus). Also, what is the (preferred) real-time programing language? I heard that Ada is used in Boeing, so my question is - why Ada? what are the criteria the Boeing-guys had to choose this language? (I guess Java wouldn't be a great choice if the exactly in lift off the garbage collector wakes up). Thanks!

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• Multilevel Queue Scheduling (MQS) with Round Robin

  - by stackuser

  I'm trying to use MQS to create a Gantt chart of 5 processes (P1-P5) as well as their waiting, response, and turnaround times (and averages of those metrics) within a CPU task schedule. Here's the basic table of arrival times and bursts: Here's my actual work version after ticking off the finished processes. The time quantum for each time slice is (2 queues) TQ1=4 and TQ2=3. Note that I'm doing MQS and NOT MLFQ: It just doesn't feel like I'm doing MQS right here, I know this gets a little complex but maybe someone can point out where I'm going totally wrong.

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• What are the safety benefits of a type system?

  - by vandros526

  In Javascript: The Good Parts by Douglas Crockford, he mentions in his inheritance chapter, "The other benefit of classical inheritance is that it includes the specification of a system of types. This mostly frees the programmer from having to write explicit casting operations, which is a very good thing because when casting, the safety benefits of a type system are lost." So first of all, what actually is safety? protection against data corruption, or hackers, or system malfunctions, etc? What are the safety benefits of a type system? What makes a type system different that allows it to provide these safety benefits?

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