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  • Add custom method to string object [closed]

    - by cru3l
    Possible Duplicate: Can I add custom methods/attributes to built-in Python types? In Ruby you can override any built-in object class with custom method, like this: class String def sayHello return self+" is saying hello!" end end puts 'JOHN'.downcase.sayHello # >>> 'john is saying hello!' How can i do that in python? Is there a normally way or just hacks?

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  • What is the cost of memory access?

    - by Jurily
    We like to think that a memory access is fast and constant, but on modern architectures/OSes, that's not necessarily true. Consider the following C code: int i = 34; int *p = &i; // do something that may or may not involve i and p {...} // 3 days later: *p = 643; What is the estimated cost of this last assignment in CPU instructions, if i is in L1 cache, i is in L2 cache, i is in L3 cache, i is in RAM proper, i is paged out to an SSD disk, i is paged out to a traditional disk? Where else can i be? Of course the numbers are not absolute, but I'm only interested in orders of magnitude. I tried searching the webs, but Google did not bless me this time.

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  • Aliasing `T*` with `char*` is allowed. Is it also allowed the other way around?

    - by StackedCrooked
    Note: This question has been renamed and reduced to make it more focused and readable. Most of the comments refer to the old text. According to the standard objects of different type may not share the same memory location. So this would not be legal: int i = 0; short * s = reinterpret_cast<short*>(&i); // BAD! The standard however allows an exception to this rule: any object may be accessed through a pointer to char or unsigned char: int i = 0; char * c = reinterpret_cast<char*>(&i); // OK However, it is not clear to me if this is also allowed the other way around. For example: char * c = read_socket(...); unsigned * u = reinterpret_cast<unsigned*>(c); // huh? Summary of the answers The answer is NO for two reasons: You an only access an existing object as char*. There is no object in my sample code, only a byte buffer. The pointer address may not have the right alignment for the target object. In that case dereferencing it would result in undefined behavior. On the Intel and AMD platforms it will result performance overhead. On ARM it will trigger a CPU trap and your program will be terminated! This is a simplified explanation. For more detailed information see answers by @Luc Danton, @Cheers and hth. - Alf and @David Rodríguez.

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  • core at which function is running

    - by kumar
    hi, consider a kernel tasklet scheduled and executing the tasklet function. Is there a way to know which core the tasklet is running ? I mean is there a function / variable to know at which core the tasklet is running at. Architecture is arm. Thanks!

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  • Solving problems with near infinite potential solutions

    - by Zonda333
    Today I read the following problem: Use the digits 2, 0, 1, 1 and the operations +, -, x, ÷, sqrt, ^ , !, (), combinations, and permutations to write equations for the counting numbers 1 through 100. All four digits must be used in each expression. Only the digits 2, 0, 1, 1 may be used, and each must be used exactly once. Decimals may be used, as in .1, .02, etc. Digits may be combined; numbers such as 20 or 101 may be used. Example: 60 = 10*(2+1)!, 54 = ¹¹C2 - 0! Though I was able to quickly find around 50 solutions quite easily in my head, I thought programming it would be a far superior solution. However, I then realized I had no clue how to go about solving a problem like this. I am not asking for complete code for me to copy and paste, but for ideas about how I would solve this problems, and others like it that have nearly infinite potential solutions. As I will be writing it in python, where I have the most experience, I would prefer if the answers were more python based, but general ideas are great too.

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  • Interpreters: Handling includes/imports

    - by sub
    I've built an interpreter in C++ and everything works fine so far, but now I'm getting stuck with the design of the import/include/however you want to call it function. I thought about the following: Handling includes in the tokenizing process: When there is an include found in the code, the tokenizing function is recursively called with the filename specified. The tokenized code of the included file is then added to the prior position of the include. Disadvantages: No conditional includes(!) Handling includes during the interpreting process: I don't know how. All I know is that PHP must do it this way as conditional includes are possible. Now my questions: What should I do about includes? How do modern interpreters (Python/Ruby) handle this? Do they allow conditional includes?

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  • Does Anyone Still Prefer N-Tier Architecture After Having *Shipped* an MVC Application?

    - by Jim G.
    Other SO threads have asked people if they prefer N-Tier or MVC architecture. I'm not looking to continue that debate on this thread. I'm looking for something more specific. My Question: Does Anyone Still Prefer N-Tier Architecture After Having Shipped an MVC Application? Reason for My Question: Before I shipped an MVC web application, I wasn't convinced that it was superior to N-Tier Architecture. Specifically, if better unit testing was the only obvious benefit of MVC, then I saw no reason to switch gears and adopt a new architecture. But after having shipped an MVC application, I can see many benefits (which have been enumerated on other threads).

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  • Class Template Instantiation: any way round this circular reference?

    - by TimYorke34
    I have two classes that I'm using to represent some hardware: A Button and an InputPin class which represent a button that will change the value of an IC's input pin when it's pressed down. A simple example of them is: template <int pinNumber> class InputPin { static bool IsHigh() { return ( (*portAddress) & (1<<pinNumber) ); } }; template <typename InputPin> class Button { static bool IsPressed() { return !InputPin::IsHigh(); } }; This works beautifully and by using class templates, the condition below will compile as tightly as if I'd handwritten it in assembly (a single instruction). Button < InputPin<1> > powerButton; if (powerButton.IsPressed()) ........; However, I am extending it to deal with interrupts and have got a problem with circular references. Compared to the original InputPin, a new InputPinIRQ class has an extra static member function that will be called automatically by the hardware when the pin value changes. I'd like it to be able to notify the Button class of this, so that the Button class can then notify the main application that it has been pressed/released. I am currently doing this with function pointers to callbacks. In order for the callback code to be inlined by the compiler, I need to pass the function pointers as template parameters. So now, both of the new classes have an extra template parameter that is a pointer to a callback function. Unfortunately this gives me a circular reference because to instantiate a ButtonIRQ class I now have to do something like this: ButtonIRQ< InputPinIRQ< A1, ButtonIRQ<....>::OnPinChange, OnButtonChange > pB; where the <...... represents the circular reference. Does anyone know how I can avoid this circular reference? I am new to templates, so might be missing something really simple. It's important that the compiler knows exactly what code will be run when the interrupt occurs as it then does some very useful optimisation - it is able to inline the callback function and literally inserts the callback function's code at the exact address that is called on a h/w interrupt.

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  • Application wide messaging... without singletons?

    - by StormianRootSolver
    So, I want to go for a more Singleton - less design in the future. However, there seem to be a lot of tasks in an application that can't be done in meaningful way without singletons. I call them "application wide services", but they also fall into the same category as the cross cutting concerns, which I usually fix via AOP. Lets take an example: I want an application wide message queue that dispatches messages to components, every component can subscribe and publish there, it's a very nice multicast thing. The message queue and dispatching system are usually a (rather short) singleton class, which is very easy to implement in, say, C#. You can even use double dispatching and utilize message type metadata and the like, it's all so easy to do, it's almost trivial. However, having singletons is not really "object oriented design" (it introduces global variables) and it makes testing harder. Do you have any ideas? I'm asking this question because I'm willing to learn more about this topic, a LOT more. :-)

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  • Graph search problem with route restrictions

    - by Darcara
    I want to calculate the most profitable route and I think this is a type of traveling salesman problem. I have a set of nodes that I can visit and a function to calculate cost for traveling between nodes and points for reaching the nodes. The goal is to reach a fixed known score while minimizing the cost. This cost and rewards are not fixed and depend on the nodes visited before. The starting node is fixed. There are some restrictions on how nodes can be visited. Some simplified examples include: Node B can only be visited after A After node C has been visited, D or E can be visited. Visiting at least one is required, visiting both is permissible. Z can only be visited after at least 5 other nodes have been visited Once 50 nodes have been visited, the nodes A-M will no longer reward points Certain nodes can (and probably must) be visited multiple times Currently I can think of only two ways to solve this: a) Genetic Algorithms, with the fitness function calculating the cost/benefit of the generated route b) Dijkstra search through the graph, since the starting node is fixed, although the large number of nodes will probably make that not feasible memory wise. Are there any other ways to determine the best route through the graph? It doesn't need to be perfect, an approximated path is perfectly fine, as long as it's error acceptable. Would TSP-solvers be an option here?

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  • Inter-rater agreement (Fleiss' Kappa, Krippendorff's Alpha etc) Java API?

    - by adam
    I am working on building a Question Classification/Answering corpus as a part of my masters thesis. I'm looking at evaluating my expected answer type taxonomy with respect to inter-rater agreement/reliability, and I was wondering: Does anybody know of any decent (preferably free) Java API(s) that can do this? I'm reasonably certain all I need is Fleiss' Kappa and Krippendorff's Alpha at this point. Weka provides a kappa statistic in it's evaluation package, but I think it can only evaluate a classifier and I'm not at that stage yet (because I'm still building the data set and classes). Thanks.

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  • Guidelines for solution source code organisation(OO/DDD)

    - by fearofawhackplanet
    I'm starting on my first business project (.NET) and am trying to follow DDD principles. Are there any guidelines or common patterns for orgaining source code and namespaces? For example, do your domain objects go in a namespace MyProject.Domain or whatever? Would you separate the concrete implementations and the interfaces? In different namespaces? Different folders? Different solutions? I know a lot of this is subjective and dependent on project size, but a few pointers or suggestions to get started on a relatively small but extensible n-tier project would be useful.

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  • What's the current (as of April 2010) state of affairs regarding <object> vs <embed> in HTML?

    - by rvdm
    The age old question. <object> vs <embed>. From what I gather, <object> is the XHTML-compliant way of doing things, while <embed> is for legacy support. I'm currently building a Flash application that will contain a pre-made embedding code for users to copy and paste, and I'm wondering if it's feasible to simply dump the <embed> tag altogether. Which browsers would be unable to load my application if I gave my users an <object>-only embed code? Thanks :)

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  • Interface explosion problem

    - by Benny
    I am implementing a screen using MVP pattern, with more feature added to the screen, I am adding more and more methods to the IScreen/IPresenter interface, hence, the IScreen/IPresenter interface is becoming bigger and bigger, what should I do to cope with this situation?

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  • Questions to ask a client before beginning a website

    - by Jason
    I am aware of this question which deals with the technical aspects of website construction, but I was unable to find any place with suggestions on knowledge you must obtain from a client before undergoing a project. As someone who freelances on the side, I think this could be incredibly useful. What important questions must one ask the client (and require an answer to) before undergoing a website? or, in other words, What must you know about the project before starting it? This can range from "When do I get paid?" to "How many pages will the site be?". I believe this is relevant to programming because you must know how to communicate with your client to get all the information necessary before you can begin programming. If not, downstream changes can put a serious delay on the project from things not hashed out beforehand. Thanks!

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  • Accessing hard-coded data in a C# application.

    - by haymansfield
    I'm trying to avaid hardcoding in a .net 2.0 soon to be 3.5 application. I have a large enumneration which I wish to map 1 to 1 to a set of strings. Each enumerated value will also map to 1 of 2 values indicating an action. The existing code does this with a big switch statement but this seems ugly to me. Is there a better way of storing and accessing the data? I've thought about resx files but when you consider that the designer file contains just as many hardcoded values it seems a little pointless. Is embedding an xml file in the assembly a good idea? Is a big switch statement not as bad as it seems? Is there a better solution?

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  • Password protect web pages on Windows CE 6

    - by Chris
    I am using the default web server for WinCE 6 and wish to password protect certain folders. The default VROOT /remoteadmin/ is password protected, and this works but my configuration doesn't work. I have tried mimicking these settings on my own folders but to little success. Here is how one looks: In the HKLM\Comm\HTTPD\VROOTS key I have created a subkey called /web/configuration (this folder actually exists on the box). The following values are in this key A = 1 DefaultPage = config.html Path = /hard disk/webroot/web/configuration/ UserList = ADMIN This is nigh on identical to the settings in /RemoteAdmin/ but /RemoteAdmin/ requests a password and /web/configuration doesn't (even after reboot).

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