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  • when to make a method static

    - by Don
    Hi, I'd like to know how people decide whether to define a method as static. I'm aware that a method can only be defined as static if it doesn't require access to instance fields. So lets say we have a method that does not access instance fields, do you always define such a method as static, or only if you need to call it statically (without a reference to an instance). Perhaps another way of asking the same question, is whether you use static or non-static as the default? Thanks, Don

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  • Unit Testing - Algorithm or Sample based ?

    - by ohadsc
    Say I'm trying to test a simple Set class public IntSet : IEnumerable<int> { Add(int i) {...} //IEnumerable implementation... } And suppose I'm trying to test that no duplicate values can exist in the set. My first option is to insert some sample data into the set, and test for duplicates using my knowledge of the data I used, for example: //OPTION 1 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //3 will be added 3 times var values = new List<int> {1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I know 3 is the only candidate to appear multiple times int counter = 0; foreach (int i in set) if (i == 3) counter++; Assert.AreEqual(1, counter); } My second option is to test for my condition generically: //OPTION 2 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //The following could even be a list of random numbers with a duplicate var values = new List<int> { 1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I am not using my prior knowledge of the sample data //the following line would work for any data CollectionAssert.AreEquivalent(new HashSet<int>(values), set); } Of course, in this example, I conveniently have a set implementation to check against, as well as code to compare collections (CollectionAssert). But what if I didn't have either ? This is the situation when you are testing your real life custom business logic. Granted, testing for expected conditions generically covers more cases - but it becomes very similar to implementing the logic again (which is both tedious and useless - you can't use the same code to check itself!). Basically I'm asking whether my tests should look like "insert 1, 2, 3 then check something about 3" or "insert 1, 2, 3 and check for something in general" EDIT - To help me understand, please state in your answer if you prefer OPTION 1 or OPTION 2 (or neither, or that it depends on the case, etc )

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  • How does C++ free the memory when a constructor throws an exception and a custom new is used

    - by Joshua
    I see the following constructs: new X will free the memory if X constructor throws. operator new() can be overloaded. The canonical definition of an operator new overload is void *operator new(heap h) and the corrisponding operator delete. The most common operator new overload is pacement new, which is void *operator new(void *p) { return p; } You almost always cannot call delete on the pointer given to placement new. This leads to a single question. How is memory cleaned up when X constructor throws and an overloaded new is used?

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  • How to differentiate between exceptions i can show the user, and ones i can't?

    - by Ian Boyd
    i have some business logic that traps some logically invalid situations, e.g. trying to reverse a transaction that was already reversed. In this case the correct action is to inform the user: Transaction already reversed or Cannot reverse a reversing transaction or You do not have permission to reverse transactions or This transaction is on a session that has already been closed or This transaction is too old to be reversed The question is, how do i communicate these exceptional cases back to the calling code, so they can show the user? Do i create a separate exception for each case: catch (ETransactionAlreadyReversedException) MessageBox.Show('Transaction already reversed') catch (EReversingAReversingTransactionException) MessageBox.Show('Cannot reverse a reversing transaction') catch (ENoPermissionToReverseTranasctionException) MessageBox.Show('You do not have permission to reverse transactions') catch (ECannotReverseTransactionOnAlredyClosedSessionException) MessageBox.Show('This transaction is on a session that has already been closed') catch (ECannotReverseTooOldTransactionException) MessageBox.Show('This transaction is too old to be reversed') Downside for this is that when there's a new logical case to show the user: Tranasctions created by NSL cannot be reversed i don't simply show the user a message, and instead it leaks out as an unhandled excpetion, when really it should be handled with another MessageBox. The alternative is to create a single exception class: `EReverseTransactionException` With the understanding that any exception of this type is a logical check, that should be handled with a message box: catch (EReverseTransactionException) But it's still understood that any other exceptions, ones that involve, for example, an memory ECC parity error, continue unhandled. In other words, i don't convert all errors that can be thrown by the ReverseTransaction() method into EReverseTransactionException, only ones that are logically invalid cause of the user.

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  • Issuing multiple requests using HTTP/1.1 Pipelining

    - by Robert S. Barnes
    When using HTTP/1.1 Pipelining what does the standard say about issuing multiple requests without waiting for each request to complete? What do servers do in practice? I ask because I once tried writing a client which would issue a batch of GET requests for multiple files and remember getting errors. I wasn't sure if it was due to me incorrectly issuing the GET's or needing to wait for each individual request to finish before issuing the next GET.

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  • How to declare class attributes in swift, just like UITableViewCell reuse identifiers?

    - by martin
    I am trying to declare a reuse identifier associated to a UITableView subclass in swift. From my understanding I would like to declare an class stored property (not an instance one) so i have access via: MyCustomTableCell.ReuseIdentifer. Here is what I was trying: class MyCustomTableViewCell : UITableViewCell { class let ReuseIdentifier = "MyCustomTableViewCellReuseIdentifier" } The compiler mentions that class attributes are not supported yet. How to declare such kind of constants associated to a class type in a clean way?

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  • [Embedded Python] Invoking a method on an object

    - by jmucchiello
    Given a PyObject* pointing to a python object, how do I invoke one of the object methods? The documentation never gives an example of this: PyObject* obj = .... PyObject* args = Py_BuildValue("(s)", "An arg"); PyObject* method = PyWHATGOESHERE(obj, "foo"); PyObject* ret = PyWHATGOESHERE(obj, method, args); if (!ret) { // check error... } This would be the equivalent of >>> ret = obj.foo("An arg")

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  • How to know if your Unit Test is "right-sized"?

    - by leeand00
    One thing that I've always noticed with my unit tests is that they get to be kind of verbose; seeing as they could also be not verbose enough, how do you get a sense of when your unit tests are the right size? I know of a good quote for this and it's: "Perfection is achieved, not when there is nothing left to add, but when there is nothing left to remove." - Antoine de Saint-Exupery.

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  • RESTful service description

    - by Anax
    From what I understand, I need to use WADL to describe a RESTful web service. Still, I have read many answers in relevant posts, where users are strongly opposed the use of WADL. What are the disadvantages of WADL? Is there any alternative solution?

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  • Are volatile data members trivially copyable?

    - by Lightness Races in Orbit
    Whilst writing this answer I realised that I'm not as confident about my conclusions as I usually would ensure before hitting Post Your Answer. I can find a couple of reasonably convincing citations for the argument that the trivial-copyability of volatile data members is either implementation defined or flat-out false: https://groups.google.com/forum/?fromgroups=#!topic/comp.std.c++/5cWxmw71ktI http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48118 http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3159.html#496 But I haven't been able to back this up in the standard1 itself. Particularly "worrying" is that there's no sign of the proposed wording change from that n3159 issues list in the actual standard's final wording. So, what gives? Are volatile data members trivially copyable, or not? 1   C++11

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  • What's the best platform for a static-website?

    - by Earlz
    Hello, I am building a static-website (as in, to change a page, we change the HTML and there is no DB or anything). Well, it will have a number of pages and I don't want to copy and paste the HTML navigation and layout code around everywhere. So what would be the best platform to use in this situation so I can have all my layout and "common" HTML markup all in one place?

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  • Why is this Scala example of implicit paremeter not working?

    - by Alex R
    simple REPL test... def g(a:Int)(implicit b:Int) = {a+b} Why do neither of these attempted usages work? 1. scala class A { var b:Int =8; var c = g(2) } :6: error: could not find implicit value for parameter b: Int class A { var b:Int =8; var c = g(2) } 2. scala class A(var b:Int) { var c = g(2) } :6: error: could not find implicit value for parameter b: Int class A(var b:Int) { var c = g(2) } ^ Thanks

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  • Organizing development teams

    - by Patrick
    A long time ago, when my company was much smaller, dividing the development work over teams was quite easy: the 'application' team developed the applications-specific logic, often requiring a deep insight of specific industry problems) the 'generic' team developed the parts that were common/generic for all applications (user interface related stuff, database access, low-level Windows stuff, ...) Over the years the boundaries between the teams have become fuzzy: the 'application' teams often write application-specific functionality with a 'generic' part, so instead of asking the 'generic' team to write that part for them, they write it themselves to speed up the developments; then donate it to the 'generic' team the 'generic' team's focus seems to be more 'maintenance oriented'. All of the 'very generic' code has already been written, so no new developments are needed in it, but instead they continuously have to support all the functionality donated by the application teams. All this seems to indicate that it's not a good idea anymore to have this split in teams. Maybe the 'generic' team should evolve into a 'software quality' team (defining and guarding the rules for writing good quality software), or into a 'software deployment' team (defining how software should be deployed, installed, ...). How do you split up the work in different teams if you have different applications? everybody can write generic code and donates it to a central 'generic' team? everybody can write generic code, but nobody 'manages' this generic code (everybody is the owner) generic code is written by a 'generic' team only and the applications have to wait until the 'generic' team delivers the generic part (via a library, via a DLL) there is no overlap in code between the different applications some other way? Notice that thee advantage of having the mix (allowing everybody to write everywhere in the code) is that: code is written in a more flexible way it's easier to debug the code since you can easily step into the 'generic' code in the debugger But the big (and maybe only) disadvantage is that this generic code may become nobody's responsibility if there is no clear team that manages it anymore. What is your vision?

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  • Capturing system command output as a string

    - by dreeves
    Perl and PHP do this with backticks. For example: $output = `ls`; This code returns a directory listing into the variable $output. A similar function, system("ls"), returns the operating system return code for the given command. I'm talking about a variant that returns whatever the command prints to stdout. (There are better ways to get the list of files in a directory; the example code is an example of this concept.) How do other languages do this? Is there a canonical name for this function? (I'm going with "backtick"; though maybe I could coin "syslurp".)

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  • Simple integer encryption

    - by tloflin
    Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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  • Would it be useful to change java to support both static and dynamic types?

    - by James A. N. Stauffer
    What if a Java allow both static and dynamic types. That might allow the best of both worlds. i.e.: String str = "Hello"; var temp = str; temp = 10; temp = temp * 5; Would that be possible? Would that be beneficial? Do any languages currently support both and how well does it work out? Here is a better example (generics can't be used but the program does know the type): var username = HttpServletRequest.getSession().getAttribute("username");//Returns a String if(username.length() == 0) { //Error }

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  • Can I use part of MD5 hash for data identification?

    - by sharptooth
    I use MD5 hash for identifying files with unknown origin. No attacker here, so I don't care that MD5 has been broken and one can intendedly generate collisions. My problem is I need to provide logging so that different problems are diagnosed easier. If I log every hash as a hex string that's too long, inconvenient and looks ugly, so I'd like to shorten the hash string. Now I know that just taking a small part of a GUID is a very bad idea - GUIDs are designed to be unique, but part of them are not. Is the same true for MD5 - can I take say first 4 bytes of MD5 and assume that I only get collision probability higher due to the reduced number of bytes compared to the original hash?

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  • Can a variable like 'int' be considered a primitive/fundamental data structure?

    - by Ravi Gupta
    A rough definition of a data structure is that it allows you to store data and apply a set of operations on that data while preserving consistency of data before and after the operation. However some people insist that a primitive variable like 'int' can also be considered as a data structure. I get that part where it allows you to store data but I guess the operation part is missing. Primitive variables don't have operations attached to them. So I feel that unless you have a set of operations defined and attached to it you cannot call it a data structure. 'int' doesn't have any operation attached to it, it can be operated upon with a set of generic operators. Please advise if I got something wrong here.

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  • Optimality of Binary Search

    - by templatetypedef
    Hello all- This may be a silly question, but does anyone know of a proof that binary search is asymptotically optimal? That is, if we are given a sorted list of elements where the only permitted operation on those objects is a comparison, how do you prove that the search can't be done in o(lg n)? (That's little-o of lg n, by the way.) Note that I'm restricting this to elements where the only operation permitted operation is a comparison, since there are well-known algorithms that can beat O(lg n) on expectation if you're allowed to do more complex operations on the data (see, for example, interpolation search). Thanks so much! This has really been bugging me since it seems like it should be simple but has managed to resist all my best efforts. :-)

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  • Determine if a Range contains a value

    - by Brad Dwyer
    I'm trying to figure out a way to determine if a value falls within a Range in Swift. Basically what I'm trying to do is adapt one of the examples switch statement examples to do something like this: let point = (1, -1) switch point { case let (x, y) where (0..5).contains(x): println("(\(x), \(y)) has an x val between 0 and 5.") default: println("This point has an x val outside 0 and 5.") } As far as I can tell, there isn't any built in way to do what my imaginary .contains method above does. So I tried to extend the Range class. I ended up running into issues with generics though. I can't extend Range<Int> so I had to try to extend Range itself. The closest I got was this but it doesn't work since >= and <= aren't defined for ForwardIndex extension Range { func contains(val:ForwardIndex) -> Bool { return val >= self.startIndex && val <= self.endIndex } } How would I go about adding a .contains method to Range? Or is there a better way to determine whether a value falls within a range? Edit2: This seems to work to extend Range extension Range { func contains(val:T) -> Bool { for x in self { if(x == val) { return true } } return false } } var a = 0..5 a.contains(3) // true a.contains(6) // false a.contains(-5) // false I am very interested in the ~= operator mentioned below though; looking into that now.

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  • C# loop - break vs. continue

    - by Terrapin
    In a C# (feel free to answer for other languages) loop, what's the difference between break and continue as a means to leave the structure of the loop, and go to the next iteration? Example: foreach (DataRow row in myTable.Rows){ if (someConditionEvalsToTrue) { break; //what's the difference between this and continue ? //continue; }}

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