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  • Supporting more than one codebase in ANSI-C

    - by Ilker Murat Karakas
    I am working on a project, with an associated Ansi-C code base. (let me call this the 'main' codebase). I now am confronted with a typical problem (stated below), which I believe I would be able to solve much easily if I had an object-oriented language at hand. The problem is this: I will have to start more than one codebases; i.e. I will have to start supporting a parallel codebase (even maybe more in the future). The initial codebases for all the new (i.e. parallel) codebases will initially be identical as the old (i.e. 'main') codebase. As we are talking about the 'C' language, I have till now been thinking of adding '#ifdef' statements to code, and writing the branch-spacific code inside those 'ifdef' blocks. Hoping that I made the problem clear (enough!), I would like to hear thoughts on clever patterns that would help me handle this problem elegantly in Ansi C. Cheers

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  • st-ordering library function?

    - by chang
    I'm in the search for an implementation of an ear-decomposition algorithm (http://www.ics.uci.edu/~eppstein/junkyard/euler/ear.html). I examined networkx and didn't find one. Although the algorithm layout is vaguely in my mind, I'd like to see some reference implementation, too. Side problem: First step could be an st-ordering of a graph. Are there any implementations for st-ordering algorithms you know? Thanks for your input. I'd really like to contribute e.g. to networkx by implementing the ear-decomposition algorithm in python.

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  • Is AMQP suitable as both an intra and inter-machine software bus?

    - by Bwooce
    I'm trying to get my head around AMQP. It looks great for inter-machine (cluster, LAN, WAN) communication between applications but I'm not sure if it is suitable (in architectural, and current implementation terms) for use as a software bus within one machine. Would it be worth pulling out a current high performance message passing framework to replace it with AMQP, or is this falling into the same trap as RPC by blurring the distinction between local and non-local communication? I'm also wary of the performance impacts of using a WAN technology for intra-machine communications, although this may be more of an implementation concern than architecture. War stories would be appreciated.

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  • Immutability of big objects

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • Statically Compiled Oracle Client Drivers/Code

    - by blockcipher
    Hello, I'm looking to write a command-line program that can execute database scripts against an Oracle server, however the machine the program will be run on may not have an Oracle client installed on it. I also don't want to rely on a language that requires a VM as there's no guarantee that the VM will be installed, so a language like C is preferable for this. Is there a way that I can statically compile/build this program and not have to have the user install the Oracle client on that machine? I'm trying to be as unobtrusive as possible. Thanks.

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  • Java multiline string

    - by skiphoppy
    Coming from Perl, I sure am missing the "here-document" means of creating a multi-line string in source code: $string = <<"EOF" # create a three line string text text text EOF In Java I have to have cumbersome quotes and plus signs on every line as I concatenate my multiline string from scratch. What are some better alternatives? Define my string in a properties file? Edit: Two answers say StringBuilder.append() is preferable to the plus notation. Could anyone elaborate as to why they think so? It doesn't look more preferable to me at all. I'm looking for away around the fact that multiline strings are not a first-class language construct, which means I definitely don't want to replace a first-class language construct (string concatenation with plus) with method calls. Edit: To clarify my question further, I'm not concerned about performance at all. I'm concerned about maintainability and design issues.

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  • Netlink user-space and kernel-space communication

    - by sasayins
    Hi, I am learning programming in embedded systems using Linux as my main platform. And I want to create a Device Event Management Service. This service is a user-space application/daemon that will detect if a connected hardware module triggered an event. But my problem is I don't know where should I start. I read about Netlink implementation for userspace-kernelspace communication and it seems its a good idea but not sure if it is the best solution. But I read that the UDEV device manager uses Netlink to wait a "uevent" from the kernel space but it is not clear for me how to do that. I read about polling sysfs but it seems it is not a good idea to poll filesystem. What do you think the implementation that should I use in my service? Should I use netlink(hard/no clue how to) or just polling the sysfs(not sure if it works)? Thanks

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  • Why doesn't C have rotate left/right operators?

    - by icepack
    A bit of a philosophical question, I suppose. Hope it belongs here. C language has the standard set of bit-wise operations, including OR, AND, XOR, SHIFT LEFT/RIGHT, NOT. Anyone has an idea why rotate left/rotate right isn't included in the language? These operators are of the same complexity as other bit-wise operators and normally require a single assembly instruction, like the others. Besides, I can think of a lot of uses for rotate operator, probably not less than, say, xor operator - so it sounds a bit strange to me that they aren't included in C along with the rest. Edit: Please stop suggesting implementations of rotation operators. I know how to do that and it's not what the question about.

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  • Is there any "standard" htonl-like function for 64 bits integers in C++ ?

    - by ereOn
    Hi, I'm working on an implementation of the memcache protocol which, at some points, uses 64 bits integer values. These values must be stored in "network byte order". I wish there was some uint64_t htonll(uint64_t value) function to do the change, but unfortunately, if it exist, I couldn't find it. So I have 1 or 2 questions: Is there any portable (Windows, Linux, AIX) standard function to do this ? If there is no such function, how would you implement it ? I have in mind a basic implementation but I don't know how to check the endianness at compile-time to make the code portable. So your help is more than welcome here ;) Thank you.

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  • Where are the new languages?

    - by Johnson William
    Most now mainstream/popular (interpreted|scripting) programming languages were created around the 1990's. (Perl, Python, Ruby, PHP just to name a few). How many people knew about those languages around 1-2 years after they had been first published? Are there languages with potential of becoming as important as e.g.: Python or PHP being developed at the moment? I mean ... is there someone even seriously trying to create a new one? If the first version of a programming language is published and nearly nobody knows about it, as it was with all the languages I've mentioned above, where could I find out? Is there some sort of "list" or "network" dealing just with non-language-specific news? Is the area where Perl, Python, Ruby and PHP fit in already fully covered? Do you know of concrete examples of new programming languages being seriously developed or rising at the moment? (Except Google's go!)

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  • Solutions for redundant server and client code?

    - by Fragsworth
    In our system, the code which exists on the client side (in Flash and Javascript) mirrors the code that exists on the server side (e.g. in Python or PHP), normally with respect to the models, the methods available for those models, and the unit tests written for them. This becomes a problem in systems where you want to minimize data transfer (e.g. multiplayer games). I do not want to write the same code and unit tests redundantly for both the client and server, but I don't know of any standard solutions to deal with this. Basically, I want a language/compiler which can produce models and methods for three main languages: Actionscript, Javascript, and any server language. Does something like this exist?

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  • Dynamic access of classes of a given namespace

    - by user322383
    Hi! I'm writing an interface that will be implemented by a lot of classes, and I'm writing a class that will hold a collection of instances of these implementations. Every class will have a default constructor. So, is there a simple way (e.g. using some kind of reflection) to put an instance of each of these implementing classes to the collection? Besides doing it manually, which is simple, yes, but a lot of work and error prone (what if I missed an implementation while writing the method? What if a new implementation came and I forgot to update the given method?). So, what I would like is to be able to iterate through all classes of a given namespace or maybe through the list of all available classes. My method then would simply check, through reflection, if the given class implements the given interface, and if it does, puts it into the collection. Thank you.

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  • Code golf - hex to (raw) binary conversion

    - by Alnitak
    In response to this question asking about hex to (raw) binary conversion, a comment suggested that it could be solved in "5-10 lines of C, or any other language." I'm sure that for (some) scripting languages that could be achieved, and would like to see how. Can we prove that comment true, for C, too? NB: this doesn't mean hex to ASCII binary - specifically the output should be a raw octet stream corresponding to the input ASCII hex. Also, the input parser should skip/ignore white space. edit (by Brian Campbell) May I propose the following rules, for consistency? Feel free to edit or delete these if you don't think these are helpful, but I think that since there has been some discussion of how certain cases should work, some clarification would be helpful. The program must read from stdin and write to stdout (we could also allow reading from and writing to files passed in on the command line, but I can't imagine that would be shorter in any language than stdin and stdout) The program must use only packages included with your base, standard language distribution. In the case of C/C++, this means their respective standard libraries, and not POSIX. The program must compile or run without any special options passed to the compiler or interpreter (so, 'gcc myprog.c' or 'python myprog.py' or 'ruby myprog.rb' are OK, while 'ruby -rscanf myprog.rb' is not allowed; requiring/importing modules counts against your character count). The program should read integer bytes represented by pairs of adjacent hexadecimal digits (upper, lower, or mixed case), optionally separated by whitespace, and write the corresponding bytes to output. Each pair of hexadecimal digits is written with most significant nibble first. The behavior of the program on invalid input (characters besides [a-fA-F \t\r\n], spaces separating the two characters in an individual byte, an odd number of hex digits in the input) is undefined; any behavior (other than actively damaging the user's computer or something) on bad input is acceptable (throwing an error, stopping output, ignoring bad characters, treating a single character as the value of one byte, are all OK) The program may write no additional bytes to output. Code is scored by fewest total bytes in the source file. (Or, if we wanted to be more true to the original challenge, the score would be based on lowest number of lines of code; I would impose an 80 character limit per line in that case, since otherwise you'd get a bunch of ties for 1 line).

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  • Inject same DataContext instance across several types with Unity

    - by Sergejus
    Suppose I have IRepository interface and its implementation SqlRepository that takes as an argument LINQ to SQL DataContext. Suppose as well that I have IService interface and its implementation Services that takes three IRepository, IRepository and IRepository. Demo code is below: public interface IRepository<T> { } public class SqlRepository<T> : IRepository<T> { public SqlRepository(DataContext dc) { ... } } public interface IService<T> { } public class Service<T,T1,T2,T3> : IService<T> { public Service(IRepository<T1> r1, IRepository<T2>, IRepository<T3>) { ... } } Is it any way while creating Service class to inject all three repositories with the same DataContext?

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  • Handling Incoming Data from Multiple Sockets in Python

    - by user859434
    Background: I have a current implementation that receives data from about 120 different socket connections in python. In my current implementation, I handle each of these separate socket connections with a dedicated thread for each. Each of these threads parse the data and eventually store it within a shared locked dictionary. These sockets DO NOT have uniform data rates, some sockets get more data than others. Question: Is this the best way to handle incoming data in python, or does python have a better way on handling multiple sockets per thread?

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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • JSF composite component - weird behavior when trying to save state

    - by jc12
    I'm using Glassfish 3.2.2 and JSF 2.1.11 I'm trying to create a composite component that will take as parameters a string and a max number of characters and then will show only the max amount of characters, but it will have a "more" link next to it, that when clicked will expand the text to the full length and will then have a "less" link next to it to take it back to the max number of characters. I'm seeing some weird behavior, so I'm wondering if I'm doing something wrong. Here is my composite component definition: <html xmlns="http://www.w3.org/1999/xhtml" xmlns:composite="http://java.sun.com/jsf/composite" xmlns:h="http://java.sun.com/jsf/html" xmlns:fn="http://java.sun.com/jsp/jstl/functions" xmlns:p="http://primefaces.org/ui"> <composite:interface componentType="expandableTextComponent"> <composite:attribute name="name" required="true"/> <composite:attribute name="maxCharacters" required="true"/> <composite:attribute name="value" required="true"/> </composite:interface> <composite:implementation> <h:panelGroup id="#{cc.attrs.name}"> <h:outputText value="#{fn:substring(cc.attrs.value, 0, cc.attrs.maxCharacters)}" rendered="#{fn:length(cc.attrs.value) le cc.attrs.maxCharacters}"/> <h:outputText value="#{fn:substring(cc.attrs.value, 0, cc.attrs.maxCharacters)}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and !cc.expanded}" style="margin-right: 5px;"/> <h:outputText value="#{cc.attrs.value}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and cc.expanded}" style="margin-right: 5px;"/> <p:commandLink actionListener="#{cc.toggleExpanded()}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters}" update="#{cc.attrs.name}"> <h:outputText value="#{__commonButton.more}..." rendered="#{!cc.expanded}"/> <h:outputText value="#{__commonButton.less}" rendered="#{cc.expanded}"/> </p:commandLink> </h:panelGroup> </composite:implementation> </html> And here is the Java component: @FacesComponent("expandableTextComponent") public class ExpandableTextComponent extends UINamingContainer { boolean expanded; public boolean isExpanded() { return expanded; } public void toggleExpanded() { expanded = !expanded; } } Unfortunately expanded is always false every time the toggleExpanded function is called. However if I change the composite component to the following then it works. <html xmlns="http://www.w3.org/1999/xhtml" xmlns:composite="http://java.sun.com/jsf/composite" xmlns:h="http://java.sun.com/jsf/html" xmlns:fn="http://java.sun.com/jsp/jstl/functions" xmlns:p="http://primefaces.org/ui"> <composite:interface componentType="expandableTextComponent"> <composite:attribute name="name" required="true"/> <composite:attribute name="maxCharacters" required="true"/> <composite:attribute name="value" required="true"/> </composite:interface> <composite:implementation> <h:panelGroup id="#{cc.attrs.name}"> <h:outputText value="#{fn:substring(cc.attrs.value, 0, cc.attrs.maxCharacters)}" rendered="#{fn:length(cc.attrs.value) le cc.attrs.maxCharacters}"/> <h:outputText value="#{fn:substring(cc.attrs.value, 0, cc.attrs.maxCharacters)}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and !cc.expanded}" style="margin-right: 5px;"/> <p:commandLink actionListener="#{cc.toggleExpanded()}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and !cc.expanded}" update="#{cc.attrs.name}" process="@this"> <h:outputText value="#{__commonButton.more}..."/> </p:commandLink> <h:outputText value="#{cc.attrs.value}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and cc.expanded}" style="margin-right: 5px;"/> <p:commandLink actionListener="#{cc.toggleExpanded()}" rendered="#{fn:length(cc.attrs.value) gt cc.attrs.maxCharacters and cc.expanded}" update="#{cc.attrs.name}" process="@this"> <h:outputText value="#{__commonButton.less}"/> </p:commandLink> </h:panelGroup> </composite:implementation> </html> If I place a breakpoint in the toggleExpanded function, it only gets called on the "more" link and not the "less" link. So the question is why doesn't it get called when I click on the "less" link? Shouldn't this code be equivalent to the code above? Is there a better way to save state in a component?

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  • How to perform duplicate key validation using entlib (or DataAnnotations), MVC, and Repository pattern

    - by olivehour
    I have a set of ASP.NET 4 projects that culminate in an MVC (3 RC2) app. The solution uses Unity and EntLib Validation for cross-cutting dependency injection and validation. Both are working great for injecting repository and service layer implementations. However, I can't figure out how to do duplicate key validation. For example, when a user registers, we want to make sure they don't pick a UserID that someone else is already using. For this type of validation, the validating object must have a repository reference... or some other way to get an IQueryable / IEnumerable reference to check against other rows already in the DB. What I have is a UserMetadata class that has all of the property setters and getters for a user, along with all of the appropriate DataAnnotations and EntLib Validation attributes. There is also a UserEntity class implemented using EF4 POCO Entity Generator templates. The UserEntity depends on UserMetadata, because it has a MetadataTypeAttribute. I also have a UserViewModel class that has the same exact MetadataType attribute. This way, I can apply the same validation rules, via attributes, to both the entity and viewmodel. There are no concrete references to the Repository classes whatsoever. All repositories are injected using Unity. There is also a service layer that gets dependency injection. In the MVC project, service layer implementation classes are injected into the Controller classes (the controller classes only contain service layer interface references). Unity then injects the Repository implementations into the service layer classes (service classes also only contain interface references). I've experimented with the DataAnnotations CustomValidationAttribute in the metadata class. The problem with this is the validation method must be static, and the method cannot instantiate a repository implementation directly. My repository interface is IRepository, and I have only one single repository implementation class defined as EntityRepository for all domain objects. To instantiate a repository explicitly I would need to say new EntityRepository(), which would result in a circular dependency graph: UserMetadata [depends on] DuplicateUserIDValidator [depends on] UserEntity [depends on] UserMetadata. I've also tried creating a custom EntLib Validator along with a custom validation attribute. Here I don't have the same problem with a static method. I think I could get this to work if I could just figure out how to make Unity inject my EntityRepository into the validator class... which I can't. Right now, all of the validation code is in my Metadata class library, since that's where the custom validation attribute would go. Any ideas on how to perform validations that need to check against the current repository state? Can Unity be used to inject a dependency into a lower-layer class library?

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  • Question about gets and sets and when to use super classes

    - by Nazgulled
    Hi, I have the following get method: public List<PersonalMessage> getMessagesList() { List<PersonalMessage> newList = new ArrayList<PersonalMessage>(); for(PersonalMessage pMessage : this.listMessages) { newList.add(pMessage.clone()); } return newList; } And you can see that if I need to change the implementation from ArrayList to something else, I can easily do it and I just have to change the initialization of newList and all other code that depends on what getMessageList() returns will still work. Then I have this set method: public void setMessagesList(ArrayList<PersonalMessage> listMessages) { this.listMessages = listMessages; } My question is, should I use List instead of `ArrayList in the method signature? I have decided to use ArrayList because this way I can force the implementation I want, otherwise there could be a mess with different types of lists here and there. But I'm not sure if this is the way to go...

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  • Cocoa: how to implement a custom NSView with an editable text area?

    - by Rinzwind
    What's the minimum implementation needed to make a custom NSView with an editable text area? I assume NSTextFieldCell can be used for this. I've succeeded in drawing the cell in the view (which is straightforward), but making it editable seems to require a more complicated coordination between the view and the cell. Is there sample code available somewhere? Update. I should have made clear that my longer-term goal is to have many more editable text areas on the same view. AFAIU it is better to use cells in that case as they are more light-weight than full-blown views. My updated question is: What's the minimum implementation needed to make a custom NSView with an editable text area using an appropriate NSCell?

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  • Fitch Format Proofs - any resources around?

    - by devoured elysium
    I am currently studying Fitch Format first order logic proofs. My lecturer follows closely Language, Proof and Logic by Jon Barwise. I am trying to do some proofs but I am having some trouble getting to understand how to do these proofs. As I have already read what Language Proof and Logic has to offer, I'd like to know if there are any other books or resources around that use the Fitch format for their formal proofs. Plus, having solved exercises would be of great(!) help. Thanks

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