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  • Programming languages: out of the box legibility and extensibility

    - by sova
    Two excellent results of SOLID development ideology are - Legibility - Extensibility over the life of a project (http://en.m.wikipedia.org/wiki/Solid_(object-oriented_design) Although SOLID is a set of language-agnostic design ideas, some languages inherently support these ideas better than others. Out-of-the-box or after various customizations, in your opinion which language is best-suited to be both easily readable and easy to extend functionality in? Some definitions to pre-empt biases and flamewars: Legibility: amount of thinking done to understand the code proportional to the amount of code: (amount_think-energy / amount_code) is fairly constant and as low as possible in the optimal case. Extensibility: Addition of X amount of functionality requires a change in code or code additions in proportion to X (amount_added_functionality / amount_added_code) is fairly constant and as high as possible in the optimal case. Supporting information and tutorials encouraged. Code snippets welcome.

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  • Aggregate functions in ANSI SQL

    - by morpheous
    I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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  • Haskell type classes and type families (cont'd)

    - by Giuseppe Maggiore
    I need some help in figuring a compiler error which is really driving me nuts... I have the following type class: infixl 7 --> class Selectable a s b where type Res a s b :: * (-->) :: (CNum n) => (Reference s a) -> (n,(a->b),(a->b->a)) -> Res a s b which I instance twice. First time goes like a charm: instance Selectable a s b where type Res a s b = Reference s b (-->) (Reference get set) (_,read,write) = (Reference (\s -> let (v,s') = get s in (read v,s')) (\s -> \x -> let (v,s') = get s v' = write v x (_,s'') = set s' v' in (x,s''))) since the type checker infers (-->) :: Reference s a -> (n,a->b,a->b->a) -> Reference s b and this signature matches with the class signature for (--) since Res a s b = Reference s b Now I add a second instance and everything breaks: instance (Recursive a, Rec a ~ reca) => Selectable a s (Method reca b c) where type Res a s (Method reca b c) = b -> Reference s c (-->) (Reference get set) (_,read,write) = \(x :: b) -> from_constant( Constant(\(s :: s)-> let (v,s') = get s :: (a,s) m = read v ry = m x :: Reference (reca) c (y,v') = getter ry (cons v) :: (c,reca) v'' = elim v' (_,s'') = set s' v'' in (y,s''))) :: Reference s c the compiler complains that Couldn't match expected type `Res a s (Method reca b c)' against inferred type `b -> Reference s c' The lambda expression `\ (x :: b) -> ...' has one argument, which does not match its type In the expression: \ (x :: b) -> from_constant (Constant (\ (s :: s) -> let ... in ...)) :: Reference s c In the definition of `-->': --> (Reference get set) (_, read, write) = \ (x :: b) -> from_constant (Constant (\ (s :: s) -> ...)) :: Reference s c reading carefully the compiler is telling me that it has inferred the type of (--) thusly: (-->) :: Reference s a -> (n,a->(Method reca b c),a->(Method reca b c)->a) -> (b -> Reference s c) which is correct since Res a s (Method reca b c) = b -> Reference s c but why can't it match the two definitions? Sorry for not offering a more succint and standalone example, but in this case I cannot figure how to do it...

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  • Circular dock/menu in css or jquery

    - by sasidhar
    Is it possible to have a circular menu or dock using css or jquery.? I have a set of images as the dock items that need to be displayed as a circular dock... however the number of items in the dock are not constant and may vary.... so i cannot tend to use constant values for positioning each item in a pre-defined manner. Ajax loads some images into this particular div and i need to use css or jquery to style this so that they get displayed as circular dock items. Any idea on how this can be implemented..? I would like a browser in-specific implementation, but i also welcome if some one has some solutions specific to few browsers... UPDATE I don't think i exactly want a pie menu... it easily gets messed up as the number of dock items increase. I am looking for a spiral dock. and by spiral i mean that the menu items must be in the following alignment..

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  • Structs inside #define in C++

    - by Adam Smith
    Being pretty new to C++, I don't quite understand some instructions I encounter such as: #ifndef BOT_H_ #define BOT_H_ #include "State.h" /* This struct represents your bot in the game of Ants */ struct Bot { State state; Bot(); void playGame(); //plays a single game of Ants void makeMoves(); //makes moves for a single turn void endTurn(); //indicates to the engine that it has made its moves }; #endif //BOT_H_ What I don't understand is the "#ifndef BOT_H_" and the "#define -- #endif" From what I gather, it defines a constant BOT_H_ if it's not already defined when the precompiler looks at it. I don't actually get how the struct inside it is a constant and how it is going to let me access the functions inside it. I also don't see why we're doing it this way? I used C++ a while back and I wasn't using .h files, so it might be something easy I'm missing.

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  • Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

    - by Mikeyg36
    I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor: public MyClass(int initialCount = 0, string name = "") Notice that he used "" instead of string.Empty. He comments: You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

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  • C++: Define simple string?

    - by Jason
    This thing is really wracking my mind. I'm learning C++ and I wanted to define a constant that I can use in another function, A short answer on how to do this will be fine.. Lets say at the beginning of my code I want to define this constant: //After #includes bool OS = 1; //1 = linux if (OS) { const ??? = "clear"; } else { const ??? = "cls"; } I don't know what type to use to define the "clear" string... I'm so confused. Later on I want to use it within a function: int foo() { system(::cls); //:: for global return 0; } How would I define the string up top, and use the string down below? I heard char only had one character and things... I'm not sure how to use , since it says it's converting string into const char or something.

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  • STL deque accessing by index is O(1)?

    - by jasonline
    I've read that accessing elements by position index can be done in constant time in a STL deque. As far as I know, elements in a deque may be stored in several non-contiguous locations, eliminating safe access through pointer arithmetic. For example: abc-defghi-jkl-mnop The elements of the deque above consists of a single character. The set of characters in one group indicate it is allocated in contiguous memory (e.g. abc is in a single block of memory, defhi is located in another block of memory, etc.). Can anyone explain how accessing by position index can be done in constant time, especially if the element to be accessed is in the second block? Or does a deque have a pointer to the group of blocks? Update: Or is there any other common implementation for a deque?

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  • Reference table values in a war against magic numbers

    - by Alex N.
    This question bugged me for years now and can't seem to find good solution still. I working in PHP and Java but it sounds like this maybe language-agnostic :) Say we have a standard status reference table that holds status ids for some kind of entity. Further let's assume the table will have just 5 values, and will remain like this for a long time, maybe edited occasionally with addition of a new status. When you fetch a row and need to see what status it is you have 2 options(as I see it at least) - put it straight ID values(magic numbers that is) or use a named constant. Latter seem much cleaner, the question though is where those named constants should leave? In a model class? In a class that uses this particular constant? Somewhere else?

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  • What are the implications of using static const instead of #define?

    - by Simon Elliott
    gcc complains about this: #include <stdio.h> static const int YY = 1024; extern int main(int argc, char*argv[]) { static char x[YY]; } $ gcc -c test1.c test1.c: In function main': test1.c:5: error: storage size of x' isn't constant test1.c:5: error: size of variable `x' is too large Remove the “static” from the definition of x and all is well. I'm not exactly clear what's going on here: surely YY is constant? I had always assumed that the "static const" approach was preferable to "#define". Is there any way of using "static const" in this situation?

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  • In WPF XAML how can I concatenate 2 constants so I can use pre-define paths?

    - by toaster24
    I'm new to XAML, so presume I'm missing something simple. I want to replace the path part of the source path with a c# constant for easier path management, for example I have: <Image Source="/Images/Themes/Buttons/MyPicture.png" /> and in another class I have my constant defined: public static readonly string UriImagesButtons = "/Images/Big/PNG/"; I want to have something along the lines of: <Image Source="{static:UriImagesButtons + MyPicture.png}" /> This means that I can change the path globally at a stroke if the need arises. What's the syntax to do this?

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  • Why the actionscript 3.0 snippet below failed to import Button and TextInput?

    - by user198729
    package { import fl.controls.Button; import fl.controls.TextInput; public class MinRecord extends Sprite { private var recordBtn:Button; private var stopBtn:Button; private var textInput:TextInput; ... When I run it reports: Type was not found or was not a compile-time constant: Button. Type was not found or was not a compile-time constant: TextInput. Can someone point out what's wrong here?

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  • Xampp error on windows

    - by Deepak Kumar
    My problem is when i use xampp i see many error and when i use my web it has no error Notice: Undefined index: action in C:\xampp\htdocs\xyz\index.php on line 3 Notice: Undefined index: usNick in C:\xampp\htdocs\xyz\config.php on line 11 Notice: Use of undefined constant setname - assumed 'setname' in C:\xampp\htdocs\xyz\config.php on line 31 Notice: Use of undefined constant setname - assumed 'setname' in C:\xampp\htdocs\xyz\config.php on line 31 Notice: Undefined index: usNick in C:\xampp\htdocs\xyz\config.php on line 34 Notice: A session had already been started - ignoring session_start() in C:\xampp\htdocs\xyz\data.php on line 2 Notice: Undefined index: r in C:\xampp\htdocs\xyz\data.php on line 4 Notice: Undefined index: ucNick in C:\xampp\htdocs\xyz\data.php on line 8 I have tried many time changing things in Setting, Security, Privileges etc but nothing changed, I want to know if im missing something out Thanks

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  • Define classes for a datatable structure - ORM

    - by user424493
    I have existing tables - I have following datatables : ActivityTable(Key ActivityId) - which lists the identifier for various activity ProcessTable (identified by ProcessId) - which lists down which activites(ActivityId) are to be carried out along with their order(StepNum). Some of the activities are marked constant with in a process, that is they will have same data, ir-respective of there run environment. RunTable(Key RunConfigurationId) - that identifies the project name and Process Id Then data for each activity is stored is stored in their individual tables Activity_A, Activity_B,Activity_C so on it uses a combination of RunConfigurationId,ProcessId and stepNum. For the activities which are constant we use a RunConfigurationId= -100. Can anybody help me out how I can map something like this in classes using inheritence regards

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  • Scope of Constants in Ruby Modules

    - by user204078
    I'm having a little problem with constant scope in mixin modules. Let's say I have something like this module Auth USER_KEY = "user" unless defined? USER_KEY def authorize user_id = session[USER_KEY] def end The USER_KEY constant should default to "user" unless it's already defined. Now I might mix this into a couple of places, but in one of those places the USER_KEY needs to be different, so we might have something like this class ApplicationController < ActionController::Base USER_KEY = "my_user" include Auth def test_auth authorize end end I would expect that USER_KEY would be "my_user" when used in authorize, since it's already defined, but it's still "user", taken from the modules definition of USER_KEY. Anyone have any idea how to get authorize to use the classes version of USER_KEY?

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  • Using inheritance with multiple files in Ruby

    - by Preethi Jain
    I am new to Ruby . I have a question with respect to using Inheritence in Ruby . I have a class called as Doggy inside a file named Doggy.rb class Doggy def bark puts "Vicky is barking" end end I have written another class named Puppy in another file named puppy.rb class Puppy < Doggy end puts Doggy.new.bark I am getting this Error: Puppy.rb:1:in `<main>': uninitialized constant Doggy (NameError) Is it mandatory to have these classes (Doggy and Puppy ) inside a single file only? Edited As per the suggestions , i have tried using require and require_relative as shown , but still i am getting below Error Puppy.rb:1:in `<main>': uninitialized constant Doggy (NameError) class Puppy < Doggy end require_relative 'Doggy.rb' puts Doggy.new.bark

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  • Good Design for Initialization of Static Array

    - by jplot
    I have a question regarding good design in C++. I have a class A, and all objects of this class use an integer array of constant values (they should share the same array, as their values are constant). The array needs to be computed (just once) before any object A. I thought about having another class B which contains the integer array as a static member, an init() method which would fill this array according to some formula and a static boolean flag initialized (if this variable if true then the init() method would do nothing), but I'm not sure this is the best way to solve my design issue. So my question is, what would be a good design/way to accomplish this ? Thanks in advance.

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  • GDC 2012: The Bleeding Edge of Open Web Tech

    GDC 2012: The Bleeding Edge of Open Web Tech (Pre-recorded GDC content) Web browsers from mobile to desktop devices are in a constant state of growth enabling ever richer and pervasive games. This presentation by Google software engineer Vincent Scheib focuses on the latest developments in client side web technologies, such as Web Sockets, WebGL, File API, Mouse Lock, Gamepads, Web Audio API and more. Speaker: Vincent Scheib From: GoogleDevelopers Views: 1279 31 ratings Time: 48:33 More in Science & Technology

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  • What is the usage of Splay Trees in the real world?

    - by Meena
    I decided to learn about balanced search trees, so I picked 2-3-4 and splay trees. What are the examples of splay trees usage in the real world? In this Cornell: http://www.cs.cornell.edu/courses/cs3110/2009fa/recitations/rec-splay.html I read that splay trees are 'A good example is a network router'. But from rest of the explanation seams like network routers use hash tables and not splay trees since the lookup time is constant instead of O(log n).

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  • Using IComparable<T> Interface

    - by Pawan_Mishra
    Level : Beginner to Intermediate C# language has constantly evolved over a constant period of time.Each new version introduced new features which changed the way we programmed and solved the problems. Whether it was introduction of generics in C# 2.0 , LINQ in C# 3.0 or concept of dynamic programming in C# 4.0 , each of them had or will have greater impact on our programming style.As a developer we don’t have much option but to evolve and redefine our self in this constantly changing environment...(read more)

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