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  • Suggestions for getting an open source electron beam tracking code going

    - by Boaz
    I work in the field of accelerator physics and synchrotron radiation. High energy electrons circulating in large rings of magnets produce x-rays that are used for a variety of different kinds of science. Running and improving these facilities requires controlling and modelling the electron beam as it circulates in the ring. A code to model this basically requires trackers to follow the electrons through the elements (something called a symplectic integrator), and then the computation of different parameters associated with this motion. The problem with these codes is that every facility has there own. In principle the code is not so complex. And as a modelling project, one might think it has some general interest. Who doesn't want to be able to create a track in space out of magnets and watch the electrons circulate? There is a Matlab based code to do this called Accelerator Toolbox, but the creator of the code is no longer in the field. I put the code in Sourceforge under the name atcollab. The basic resource is in C- it is the set of symplectic integrators. These are available in the atcollab code here. It has been useful to put the code on Sourceforge in order to exchange code, but the community of users is quite small and most are too busy to put that much time into collaboration. So in terms of really improving the code, I don't think it has been so successful. Any piece of this picture could be recreated without that much difficulty, but overall it is a bit complex, and because each lab has their own installation with lots of add-on Matlab code, people find it hard to really work together and share code. Somehow I think we need to involve a wider community in our development, or just use some standard tools. But for that, I suppose it needs to be of some general interest. I think symplectic integrators may have some general interest. And the part about a plug-in architecture to build up the ring ought to fit other patterns. Or the other option is to just accept that this is not a problem of general interest, and work harder within our small community. Suggestions, or anecdotes of analogous experience would be appreciated.

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  • Suggested HTTP REST status code for 'request limit reached'

    - by Andras Zoltan
    I'm putting together a spec for a REST service, part of which will incorporate the ability to throttle users service-wide and on groups of, or on individual, resources. Equally, time-outs for these would be configurable per resource/group/service. I'm just looking through the HTTP 1.1 spec and trying to decide how I will communicate to a client that a request will not be fulfilled because they've reached their limit. Initially I figured that client code 403 - Forbidden was the one, but this, from the spec: Authorization will not help and the request SHOULD NOT be repeated bothered me. It actually appears that 503 - Service Unavailable is a better one to use - since it allows for the communication of a retry time through the use of the Retry-After header. It's possible that in the future I might look to support 'purchasing' more requests via eCommerce (in which case it would be nice if client code 402 - Payment Required had been finalized!) - but I figure that this could equally be squeezed into a 503 response too. Which do you think I should use? Or is there another I've not considered?

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  • Is there a programming language with not a tree but tags idea behind OOP?

    - by kolupaev
    I'm thinking about tree structures, and I feel that I don't like them. It's like when you have a shop, then you try to put all products to tree-like catalog, and then you need to place one product to multiple categories, now you have multiple routing, bla-bla. I don't feel like everything in the world could be put to a tree. Instead, I like idea of tags. I would like to store everything with tags. With tags I could do much more. I can even simulate trees if I want. I want to have tag-based filesystem! But hey - modern OOP paradigm with inheritance is based on tree. I want to see how it is when you don't have such basement. Closest thing I found is mixins in some languages. Do you know what else is also about this ideas?

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  • Concurrency checking with Last Change Time

    - by Lijo
    I have a following three tables Email (emailNumber, Address) Recipients (reportNumber, emailNumber, lastChangeTime) Report (reportNumber, reportName) I have a C# application that uses inline queries for data selection. I have a select query that selects all reports and their Recipients. Recipients are selected as comma separacted string. During updating, I need to check concurrency. Currently I am using MAX(lastChangeTime) for each reportNumber. This is selected as maxTime. Before update, it checks that the lastChangeTime <= maxTime. --//It works fine One of my co-developers asked why not use GETDATE() as “maxTime” rather than using a MAX operation. That is also working. Here what we are checking is the records are not updated after the record selection time. Is there any pitfalls in using GETDATE() for this purpose?

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  • Can someone provide a short code example of compiler bootstrapping?

    - by Jatin
    This Turing award lecture by Ken Thompson on topic "Reflections on Trusting Trust" gives good insight about how C compiler was made in C itself. Though I understand the crux, it still hasn't sunk in. So ultimately, once the compiler is written to do lexical analysis, parse trees, syntax analysis, byte code generation etc, a separate machine code is again written to do all that on compiler? Can anyone please explain with a small example of the procedure? Bootstrapping on wiki gives good insights, but only a rough view on it. PS: I am aware of the duplicates on the site, but found them to be an overview which I am already aware

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  • Introducing Agile development after traditional project inception

    - by Riggy
    About a year and a half ago, I entered a workplace that claimed to do Agile development. What I learned was that this place has adopted several agile practices (such as daily standups, sprint plannings and sprint reviews) but none of the principles (just in time / just good enough mentality, exposing failure early, rich communication). I've now been tasked with making the team more agile and I've been assured that I have complete buy-in from the devs and the business team. As a pilot program, they've given me a project that just completed 15 months of requirements gathering, has a 110 page Analysis & Design document (to be considered as "written in stone"), and where I have no access to the end users (only to the committee made up of the users' managers who won't actually be using the product). I started small, giving them a list of expected deliverables for the first 5 sprints (leaving the future sprints undefined), a list of goals for the first sprint, and I dissected the A&D doc to get enough user stories to meet the first sprint's goals. Since then, they've asked why we don't have all the requirements for all the sprints, why I haven't started working on stuff for the third sprint (which they consider more important but is based off of the deliverables of the first 2 sprints) and are pressing for even more documentation that my entire IT team considers busy-work or un-related to us (such as writing the user manual up-front, documenting all the data fields from all the sprints up front, and more "up-front" work). This has been pretty rough for me as a new project manager, but there are improvements I have effectively implemented such as scrumban for story management, pair programming, and having the business give us customer acceptance tests up front (as part of the requirements documentation). So my questions are: What can I do to more effectively introduce change to a resistant business? Are there other practices that I can introduce on the IT side to help show the business the benefits of agile? The burden of documentation is strangling us - the business still sees it as a risk management strategy instead of as a risk. What can we do to alleviate their documentation concerns and demands (specifically the quantity of documentation and their need for all of it up front)? We are in a separate building from our business, about 3 blocks away and they refuse to have their people on the project co-habitate b/c that person "won't be able to work on their other projects while they're at our building." They expect us to always go over there and to bundle our questions so that we can ask them all at once and not waste that person's time with "constant interruptions." What can we do to get richer communication from them? Any additional advice would also be appreciated. Thanks!

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  • Need personal advice on how to get out of a company..

    - by SOfan
    Hi, I am an SO user since past 6 months and this is the first time I am turning to SO for personal help. I have asked technical questions before with my real ID. I am stuck inside a service based IT company for the past one year and haven't been able to decide if to leave it, when to leave it and how to leave it. I had taken 2 weeks LWP on medical reason roughly at end of 1 year and then soon after reporting, I applied for 2 months more LWP (on medical/personal ground) with the intention of working on my health,take up a hobby class to ward off depression,pessimism, to have some fun in life, and to look for a job which I really would be excited about - that interests me and which matches with my strength. My leave starts from this Monday. So in any case, I had hard set in mind that I will leave the company after I join them back hopefully with some job offer already in hand (after figuring out what I want do). Neither I can stand the past project,past colleagues,company, HR, pathetically low salary. But if I really listen to my heart, I don't want to have to go back to that office after my sabbatical and again have to see those people. I will have to resign it after my sabbatical ends. Then HR people perhaps wont like it, may even accuse me on face or behind back that primary purpose of my leave must have been to hunt for a better job and I lied about medical and person reasons. Also, if they get nasty and force me to serve 2 months notice period. There is no way I see myself after sabbatical resuming in old project or starting new work. It will be a pain. Since they have already approved 2 months leave and stuff, ideally if they want, they should be just able to relieve me right on the next day after I join back. But, I don't know if they want to get nasty, will they mention about my 2 months sabbatical leave in my experience letter or more scary, the term medical/personal reason. I have hard earned my experience here, have worked against my will, mostly it has been painful and slogged like anything, because I realize the importance of work experience in IT industry. I don't have greed to have those 2 months included extra in my experience letter, but I don't want to mess up with my experience letter in a way which makes my next employer ask question, get suspicious, or be wary if I have any medical reason going on. Being an emotional,moody person or somebody who can't be in an environment, once my mind and heart starts hating it. I think it perhaps is best, if I resign on Monday itself telling them (in polite manner) something that look I took sabbatical for some reason but I don't want to resume working in the company after my sabbatical ends. So please accept my resignation. Now tell me what you want to do about my leave request, my notice period and when you are willing to relieve me. What should I write and how? Some background: I am working in an IT company in India.I am overqualified in the company. It is grossly underpaying me. My education qualifications far exceed anyone's in the whole company being a CS undergrad as well as a CS grad. I joined this company after finishing the grad. I had self-doubts about my skills and interest as a programmer. I like doing research oriented work, though didn't have any particular success during grad. My life here has been very hectic. The project containing many many sub-projects has kept me on my toes and I have never really liked the work. I have been playing against my strength. Also the company strict internet usage policy (you can't read gmails, can't browse any non-work related sites not even news). When working for a client, from the machine we can't even check company related emails.For this one has to go to kiosk like 5 machines in a small room etc. Most of the times those machines are not available, so it was not unusual to keep making rounds to these kiosk machines to check company emails, browse company related emails etc.So it was not so easy to keep in touch with company related basic affairs for a not particular careful person. Things like this which are new to me, make me feel restricted. I am an undecisive person with a sense of failure, self-doubt, not meeting up unrealistic expectation. Somewhere at back of mind, I envy my classmates who make a smooth transition from company to company without causing any gap in their resume. I on other hand have gaps in resume. I get tired after working in a place for sometime. problem with colleagues in general. I am not particular great with people, have few friends, not known for a fun nature, rather serious, scholar. I am not a typical conventional female. I think females are usually more disciplined. But I am not so. I reach office late (though after informing manager). I don't want to blame them entirely, because from my past, it is not unusual for me to get undecisive on things. Also I had doubts about my ability as researched and to succeed there. of building a relationship in a group, to have something to talk about, newspaper. I get cut-off from people. peer pressure. I make blunders in coding, lose patience. Consciously or unconsciously I feel contempt for people here, work here, environment here. I have doubts that either I go to a place which does innovation, does research oriented work, product biggies, have great motivated people, have competent people passionate about products they are building. But then I also doubt my ability to survive there. I have identified that an idea job for me would be 4 days a week, a high salary job. When among people in company/team, I can't think much. I need some time at home to read good authentic books written in good style on what work I am doing.So that I am comfortable with my understanding of work. I get into pressure easily under deadline and need 5th day to cool myself off. I took for 2 weeks leave, because each day was hell for me. May be the depression phase of bipolar is on and also partially it could be that being a work centered person, who derives happiness,self-esteem from work, haven't been enjoying work and have been working for the sole person of proving stability, and ability to stick, against all odds, and facing what challenges I see, bonding with people, identifying opportunities to learn in given task etc.have been averaging one day LWP in 1 week or 10 days. or may be because of my nature,ADD,not being able to switch context,out of touch with news, don't have a circle of friends with who I enjoy. less knowledge in general to talk about, just some technical stuff.anyway, so due to emotional reason, some practical reason etc, I wanted to be very sure before leaving. So my leave starts from Monday and I should feel happy about it. I have taken the leave to for a few purposes - to take care of my health by regular yoga/exercise (with project on, I just can't do anything regular), reassess myself to see what I want to try next which work I might like, look for next job, take up a hobby which I like say singing. I am not clear on my career,job aspiration. I have tried my hands on research. During this year appraisal yesterday, I even had some conflict with my last manager. In meeting with me one on one, he would say all nice things about me, but in feedback to new manager, he hasn't given any excellent feedback. It is all only good. I am angry at this old Manager. Also new manager also scolded me as I didn't agree to his appraisal and waited to hear myself from old Manager. He kind of scolded me for wasting his time. Am I being unethical somewhere? I am always very conscious of if I am cheating anywhere. What advice I am seeking? How to resign and what to write in resignation letter

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  • How could we rewrite the 'No Evil' license to make it 'free'?

    - by passcod
    I did not find the lawyers' SE site, so I thought it best to post here. /* * ...subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * The Software shall be used for Good, not Evil. * * THE SOFTWARE IS PROVIDED "AS IS"... */ This is the 'non-free', Crockford, No-Evil, MIT-style, license. This license is considered non-free because of this phrase: "The Software shall be used for Good, not Evil." How could we rewrite this to become a 'free' license, while retaining the original spirit of the sentence?

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  • Can someone recommend an appriopriate drawing tablet that fits my needs?

    - by Syg
    I'm looking for something that can help me to easily create small hand drawn graphics and mock-ups digitalize technical drawings I would normally draw on a whiteboard. I'm a developer, not a designer, so it doesn't have to be high-end I guess. Just something to help make it easier, more fun and more productive to quickly draw mockups etc. After a quick search I landed on the wacom site, but it's hard for me to tell the difference between the offerings never having used something like this. Is small too small? is it annoying? Other suggestion are also welcome ofcourse. Thanx for any help you can give me

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  • What are the best Microsoft Certifications to start with?

    - by emragins
    Background I have a bachelors in math and a certification. in C++ from 2007. Since then I've spent a lot of time working with python, C#, and started going through the ASP.NET certification materials. I'm starting to realize that the certification is going to take longer than anticipated and I'm not sure I want to spend the next 4-5 months studying before I have it completed. Most of resume shows teaching/tutoring experience with some low-level administration thrown in. Question If I want to get any programming position, which certifications would be best to start with? What would be the quickest and easiest to obtain, yet represent value for my employer? Are certifications even the way to go? If not, what would you suggest? Update I have several programs that I show off when I can (mostly games), and I'm about 75% through a C# application I hope to have done in the next week. Since most employers simply ask for a resume and not samples, what would be the best way to present the work to them?

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  • Any suggestions how it would be good to promote software in a small company ?

    - by Derfder
    Ok, I know if I am Red hat or other giant and offer some support etc. I can be profitable, in fact, Red Hat is doing quite well. However, what about a small company where I create a small program. e.g. an instant messenger for a windows or linux (just as an illustration) and I want to sell it. But how can I sell it if it is free and everybody can download it? Any advice? I like the idea of FSF by Richard Stallman, however I am missing the way how to sell my software under GNU/GPL licence. Any advice, how can I solve this problem? Any profitable small business software developers around with their opinion? Any links or names of small companies taht I can look at and study their model of business?

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  • Why is a small fixed vocabulary seen as an advantage to RESTful services?

    - by Matt Esch
    So, a RESTful service has a fixed set of verbs in its vocabulary. A RESTful web service takes these from the HTTP methods. There are some supposed advantages to defining a fixed vocabulary, but I don't really grasp the point. Maybe someone can explain it. Why is a fixed vocabulary as outlined by REST better than dynamically defining a vocabulary for each state? For example, object oriented programming is a popular paradigm. RPC is described to define fixed interfaces, but I don't know why people assume that RPC is limited by these contraints. We could dynamically specify the interface just as a RESTful service dynamically describes its content structure. REST is supposed to be advantageous in that it can grow without extending the vocabulary. RESTful services grow dynamically by adding more resources. What's so wrong about extending a service by dynamically specifying a per-object vocabulary? Why don't we just use the methods that are defined on our objects as the vocabulary and have our services describe to the client what these methods are and whether or not they have side effects? Essentially I get the feeling that the description of a server side resource structure is equivalent to the definition of a vocabulary, but we are then forced to use the limited vocabulary in which to interact with these resources. Does a fixed vocabulary really decouple the concerns of the client from the concerns of the server? I surely have to be concerned with some configuration of the server, this is normally resource location in RESTful services. To complain at the use of a dynamic vocabulary seems unfair because we have to dynamically reason how to understand this configuration in some way anyway. A RESTful service describes the transitions you are able to make by identifying object structure through hypermedia. I just don't understand what makes a fixed vocabulary any better than any self-describing dynamic vocabulary, which could easily work very well in an RPC-like service. Is this just a poor reasoning for the limiting vocabulary of the HTTP protocol?

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  • I need recommendations on free, open source, PHP-based business intelligence widget frameworks [on hold]

    - by Volomike
    I'm a PHP developer on Linux, and my manager wants a business intelligence dashboard. He wants to see in real-time our profit/loss stuff in fancy charts, based on our software sales. I could code it all from scratch and use Google Charts API or some other charts API to help me. However, I wanted to know if there was a free, open source, PHP-based business intelligence package out there, or some sort of widget framework that I could start with. That way, I can build the BI widgets inside that framework and not have to do everything from scratch. I apologize ahead of time if this is the wrong stackexchange where to place this query. I don't know where to place this query, and do want to follow the rules.

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  • SSO between multiple Flex applications

    - by KarthiPk
    We have three applications developed in Flex and all these use BlazeDS. These applications have their own authentication implementations (Database). Also they will be deployed in tomcat. Deploying all these applications in the same tomcat instance is acceptable for us. We want to bring the authentication credentials of all these applications into a single place and also provide SSO feature between these applications. We also want the authentication module to be configurable. Something like the system administrator can decide if the authentication should be done against a database or LDAP. Say, if the user successfully logs into app1, and when he access app2 in the same browser he should be automatically logged in. Same goes for logout as well. We have been exploring OpenAM, jGuard and JOSSO. I'm not sure if these require lot of customization to work with Flex. I would like to know how people are implementing SSO for Flex applications. Is there a common and simple SSO solution available for Flex based applications ?

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  • Reading mp3 metadata?

    - by Blaze
    I am planing on writing an application using Vala. Its purposed is to import mp3 files from a location and rename them if necessary. The renaming information should be provided by the ID3 tags in the mp3 file such as the title and the number of the song. My target platform is Ubuntu (Linux). As the question says, I am searching for how can I achieve this on Vala. I think this functionality might be provided by Gstreamer.

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  • What is considered third party code?

    - by Songo
    Inspired by this question Using third-party libraries - always use a wrapper? I wanted to know what people actually consider as third-party libraries. Example from PHP: If I'm building an application using Zend framework, should I treat Zend framework libraries as third party code? Example from C#: If I'm building a desktop application, should I treat all .Net classes as third party code? Example from Java: Should I treat all libraries in the JDK as third party libraries? Some people say that if a library is stable and won't change often then one doesn't need to wrap it. However I fail to see how one would test a class that depends on a third party code without wrapping it.

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  • Rewriting GPL code to change license

    - by I_like_traffic_lights
    I have found a GPL library (no dual license), which does exactly what I need. Unfortunately, the GPL license on the library is incompatible with the license of a different library I use. I have therefore decided to rewrite the GPL library, so the license can be changed. My question is: How extensive do the changes need to be to the library in order to be able to change the license? In other words, what is the cheapest way to do this?

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  • Solutions for Project management [closed]

    - by user14416
    The team consists of 3 people. The method of development is Scrum. The language of the project is C++. The project will be under the control of the git system. The start up budget is 0. The following things have to be chosen: Build and Version Numbering Project documentation ( file with the most common info for current stage of the project, which will be changed every time the new version or subversion of the project emerges ) Project management tool ( like Trac or Redmine, I cannot use them, because there is no hosting ) Code documentation ( I consider Doxygen ) The following questions have arisen: What can you add to the above list of the main solutions for project management in the described project? One of three project participants has linux os (No MS Office), one has Windows and MS Office (does not want to use Libre or Open Office), one has Windows, but does not have MS Office. What formats, tools can u suggest using for project documentation? The variant of using online wiki does not fit, it must be files. OneNote mb is a good tool for project management, but because of the reason mentioned above it is not possible. What can you advise? Offer a system for Build and Version Numbering.

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  • Best practices for using namespaces in C++.

    - by Dima
    I have read Uncle Bob's Clean Code a few months ago, and it has had a profound impact on the way I write code. Even if it seemed like he was repeating things that every programmer should know, putting them all together and putting them into practice does result in much cleaner code. In particular, I found breaking up large functions into many tiny functions, and breaking up large classes into many tiny classes to be incredibly useful. Now for the question. The book's examples are all in Java, while I have been working in C++ for the past several years. How would the ideas in Clean Code extend to the use of namespaces, which do not exist in Java? (Yes, I know about the Java packages, but it is not really the same.) Does it make sense to apply the idea of creating many tiny entities, each with a clearly define responsibility, to namespaces? Should a small group of related classes always be wrapped in a namespace? Is this the way to manage the complexity of having lots of tiny classes, or would the cost of managing lots of namespaces be prohibitive?

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  • Creating an expandable, cross-platform compatible program "core".

    - by Thomas Clayson
    Hi there. Basically the brief is relatively simple. We need to create a program core. An engine that will power all sorts of programs with a large number of distinct potential applications and deployments. The core will be an analytics and algorithmic processor which will essentially take user-specific input and output scenarios based on the information it gets, whilst recording this information for reporting. It needs to be cross platform compatible. Something that can have platform specific layers put on top which can interface with the core. It also needs to be able to be expandable, for instance, modular with developers being able to write "add-ons" or "extensions" which can alter the function of the end program and can use the core to its full extent. (For instance, a good example of what I'm looking to create is a browser. It has its main core, the web-kit engine, for instance, and then on top of this is has a platform-specific GUI and can also have add-ons and extensions which can change the behavior of the program.) Our problem is that the extensions need to interface directly with the main core and expand/alter that functionality rather than the platform specific "layer". So, given that I have no experience in this whatsoever (I have a PHP background and recently objective-c), where should I start, and is there any knowledge/wisdom you can impart on me please? Thanks for all the help and advice you can give me. :) If you need any more explanation just ask. At the moment its in the very early stages of development, so we're just researching all possible routes of development. Thanks a lot

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  • Changes in Language Punctuation [closed]

    - by Wes Miller
    More social curiosity than actual programming question... (I got shot for posting this on Stack Overflow. They sent me here. At least i hope here is where they meant.) Based on the few responses I got before the content police ran me off Stack Overflow, I should note that I am legally blind and neatness and consistency in programming are my best friends. A thousand years ago when I took my first programming class (Fortran 66) and a mere 500 years ago when I tokk my first C and C++ classes, there were some pretty standard punctuation practices across languages. I saw them in Basic (shudder), PL/1, PL/AS, Rexx even Pascal. Ok, APL2 is not part of this discussion. Each language has its own peculiar punctuation. Pascal's periods, Fortran's comma separated do loops, almost everybody else's semicolons. As I learned it, each language also has KEYWORDS (if, for, do, while, until, etc.) which are set off by whitespace (or the left margin) if, etc. Each language has function, subroutines of whatever they're called. Some built-in some user coded. They were set off by function_name( parameters );. As in sqrt( x ) or rand( y ); Lately, there seems to be a new set of punctuation rules. Especially in c++ where initializers get glued onto the end of variable declarations int x(0); or auto_ptr p(new gizmo); This usually, briefly fools me into thinking someone is declaring a function prototype or using a function as a integer. Then "if" and 'for' seems to have grown parens; if(true) for(;;), etc. Since when did keywords become functions. I realize some people think they ARE functions with iterators as parameters. But if "for" is a function, where did the arg separating commas go? And finally, functions seem to have shed their parens; sqrt (2) select (...) I know, I koow, loosening whitespace rules is good. Keep reading. Question: when did the old ways disappear and this new way come into vogue? Does anyone besides me find it irritating to read and that the information that the placement of punctuation used to convey is gone? I know full well that K&R put the { at the end of the "if" or "for" to save a byte here and there. Can't use that excuse here. Space as an excuse for loss of readability died as HDD space soared past 100 MiB. Your thoughts are solicited. If there is a good reason to do this, I'll gladly learn it and maybe in another 50 years I'll get used to it. Of course it's good that compilers recognize these (IMHO) typos and keep right on going, but just because you CAN code it that way doesn't mean you HAVE to, right?

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  • Relationships in a Chen ERD

    - by Nibroc A Rehpotsirhc
    I am working on a Chen ERD to model our organizations merchandise. Our central entity is a Style. We have supplemental entities of Color and Season. I am defining our assortment as the relationship between these three entities, and this relationship itself will have attributes and is defined by the three entities which participate in the mandatory relationship. The rules are; Many Styles can be offered in a Season, and a Style can be offered in many Seasons. Within a Season, a Style can be offered in Many Colors. I then have 2 other entities, one of which I believe is a weak entity, Climate, and the other may be weak, but I am not sure, this being Transaction Channel. I am thinking of these as relationships off of a relationship? Meaning, for a given Style/Color combination offered in a Season, it can be available through 1 or more Transaction Channels. Additionally, within a season, a given Style/Color combination can be intended for 1 or more Climates. Is it valid to have relationships off of relationships? Or does this requirement dictate that I should think of this Style/Color/Season relationship as an entity itself, and define the relationships to Climate and Transaction Channel off of this entity?

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  • Help needed with pyparsing [closed]

    - by Zearin
    Overview So, I’m in the middle of refactoring a project, and I’m separating out a bunch of parsing code. The code I’m concerned with is pyparsing. I have a very poor understanding of pyparsing, even after spending a lot of time reading through the official documentation. I’m having trouble because (1) pyparsing takes a (deliberately) unorthodox approach to parsing, and (2) I’m working on code I didn’t write, with poor comments, and a non-elementary set of existing grammars. (I can’t get in touch with the original author, either.) Failing Test I’m using PyVows to test my code. One of my tests is as follows (I think this is clear even if you’re unfamiliar with PyVows; let me know if it isn’t): def test_multiline_command_ends(self, topic): output = parsed_input('multiline command ends\n\n',topic) expect(output).to_equal( r'''['multiline', 'command ends', '\n', '\n'] - args: command ends - multiline_command: multiline - statement: ['multiline', 'command ends', '\n', '\n'] - args: command ends - multiline_command: multiline - terminator: ['\n', '\n'] - terminator: ['\n', '\n']''') But when I run the test, I get the following in the terminal: Failed Test Results Expected topic("['multiline', 'command ends']\n- args: command ends\n- command: multiline\n- statement: ['multiline', 'command ends']\n - args: command ends\n - command: multiline") to equal "['multiline', 'command ends', '\\n', '\\n']\n- args: command ends\n- multiline_command: multiline\n- statement: ['multiline', 'command ends', '\\n', '\\n']\n - args: command ends\n - multiline_command: multiline\n - terminator: ['\\n', '\\n']\n- terminator: ['\\n', '\\n']" Note: Since the output is to a Terminal, the expected output (the second one) has extra backslashes. This is normal. The test ran without issue before this piece of refactoring began. Expected Behavior The first line of output should match the second, but it doesn’t. Specifically, it’s not including the two newline characters in that first list object. So I’m getting this: "['multiline', 'command ends']\n- args: command ends\n- command: multiline\n- statement: ['multiline', 'command ends']\n - args: command ends\n - command: multiline" When I should be getting this: "['multiline', 'command ends', '\\n', '\\n']\n- args: command ends\n- multiline_command: multiline\n- statement: ['multiline', 'command ends', '\\n', '\\n']\n - args: command ends\n - multiline_command: multiline\n - terminator: ['\\n', '\\n']\n- terminator: ['\\n', '\\n']" Earlier in the code, there is also this statement: pyparsing.ParserElement.setDefaultWhitespaceChars(' \t') …Which I think should prevent exactly this kind of error. But I’m not sure. Even if the problem can’t be identified with certainty, simply narrowing down where the problem is would be a HUGE help. Please let me know how I might take a step or two towards fixing this.

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

    - by Meena
    I decided to learn about Balance search trees, so I picked 2-3-4 and splay trees. I'm wondering 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). thanks!

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  • How do I cleanly design a central render/animation loop?

    - by mtoast
    I'm learning some graphics programming, and am in the midst of my first such project of any substance. But, I am really struggling at the moment with how to architect it cleanly. Let me explain. To display complicated graphics in my current language of choice (JavaScript -- have you heard of it?), you have to draw graphical content onto a <canvas> element. And to do animation, you must clear the <canvas> after every frame (unless you want previous graphics to remain). Thus, most canvas-related JavaScript demos I've seen have a function like this: function render() { clearCanvas(); // draw stuff here requestAnimationFrame(render); } render, as you may surmise, encapsulates the drawing of a single frame. What a single frame contains at a specific point in time, well... that is determined by the program state. So, in order for my program to do its thing, I just need to look at the state, and decide what to render. Right? Right. But that is more complicated than it seems. My program is called "Critter Clicker". In my program, you see several cute critters bouncing around the screen. Clicking on one of them agitates it, making it bounce around even more. There is also a start screen, which says "Click to start!" prior to the critters being displayed. Here are a few of the objects I'm working with in my program: StartScreenView // represents the start screen CritterTubView // represents the area in which the critters live CritterList // a collection of all the critters Critter // a single critter model CritterView // view of a single critter Nothing too egregious with this, I think. Yet, when I set out to flesh out my render function, I get stuck, because everything I write seems utterly ugly and reminiscent of a certain popular Italian dish. Here are a couple of approaches I've attempted, with my internal thought process included, and unrelated bits excluded for clarity. Approach 1: "It's conditions all the way down" // "I'll just write the program as I think it, one frame at a time." if (assetsLoaded) { if (userClickedToStart) { if (critterTubDisplayed) { if (crittersDisplayed) { forEach(crittersList, function(c) { if (c.wasClickedRecently) { c.getAgitated(); } }); } else { displayCritters(); } } else { displayCritterTub(); } } else { displayStartScreen(); } } That's a very much simplified example. Yet even with only a fraction of all the rendering conditions visible, render is already starting to get out of hand. So, I dispense with that and try another idea: Approach 2: Under the Rug // "Each view object shall be responsible for its own rendering. // "I'll pass each object the program state, and each can render itself." startScreen.render(state); critterTub.render(state); critterList.render(state); In this setup, I've essentially just pushed those crazy nested conditions to a deeper level in the code, hiding them from view. In other words, startScreen.render would check state to see if it needed actually to be drawn or not, and take the correct action. But this seems more like it only solves a code-aesthetic problem. The third and final approach I'm considering that I'll share is the idea that I could invent my own "wheel" to take care of this. I'm envisioning a function that takes a data structure that defines what should happen at any given point in the render call -- revealing the conditions and dependencies as a kind of tree. Approach 3: Mad Scientist renderTree({ phases: ['startScreen', 'critterTub', 'endCredits'], dependencies: { startScreen: ['assetsLoaded'], critterTub: ['startScreenClicked'], critterList ['critterTubDisplayed'] // etc. }, exclusions: { startScreen: ['startScreenClicked'], // etc. } }); That seems kind of cool. I'm not exactly sure how it would actually work, but I can see it being a rather nifty way to express things, especially if I flex some of JavaScript's events. In any case, I'm a little bit stumped because I don't see an obvious way to do this. If you couldn't tell, I'm coming to this from the web development world, and finding that doing animation is a bit more exotic than arranging an MVC application for handling simple requests - responses. What is the clean, established solution to this common-I-would-think problem?

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