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• Query something and return the reason if nothing has been found

  - by Daniel Hilgarth

  Assume I have a Query - as in CQS that is supposed to return a single value. Let's assume that the case that no value is found is not exceptional, so no exception will be thrown in this case. Instead, null is returned. However, if no value has been found, I need to act according to the reason why no value has been found. Assuming that the Query knows the reason, how would I communicate it to the caller of the Query? A simple solution would be not return the value directly but a container object that contains the value and the reason: public class QueryResult { public TValue Value { get; private set; } public TReason ReasonForNoValue { get; private set; } } But that feels clumsy, because if a value is found, ReasonForNoValue makes no sense and if no value has been found, Value makes no sense. What other options do I have to communicate the reason? What do you think of one event per reason? For reference: This is going to be implemented in C#.

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• I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

  - by tieTYT

  My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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• Best scripting language for project [on hold]

  - by Dave

  This is a subjective question, but I don't know where else to ask it. I'd appreciate it if someone could direct me to an appropriate scripting language for my project. I'm a little new at this so I'd appreciate any help. The project is a website that will display a list of photo subject groups (such as "nature" "people" "sports" etc) on the home page. The photos will all be in subdirectories of the main photo directory (photos) and each subject group will represent a subdirectory in photos. For example in directory photos there might be 3 subdirectories, "nature" "people" "sports" and in each of those subdirectories there will be the actual photos. The idea is that when the website owner wants to update/add/delete a subject group all he has to do is add, delete or update a subdirectory of the photos directory. This means, I think, that I need a scripting language that can read the directories and files in the website and then send a web page with the information in it. What is the simplest and easiest scripting language to do this in? Any ideas? Thanks

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• generating maps

  - by gardian06

  This is a conglomeration question when answering please specify which part you are addressing. I am looking at creating a maze type game that utilizes elevation. I have a few features I would like to have, but am unsure as to some of the implementation. I have done work doing fileIO maze generation (using a key to read the file, and then generate the level based on that file), but I am unsure how to think about this with elevation in the mix. I think height maps might be a good approach, but don't know how to represent them effectively. for a height map which is more beneficial XML(containing h[u,v] data and key definition), CSV (item1 is key reference, item2 is elevation), or another approach that I have not thought of yet? When it comes to placing the elevation values themselves what kind of deltah values are appropriate to have it noticeable at about a 60degree angle while not really effecting gravity driven physics (assuming some effect while moving up/down hill)? I am thinking of maybe going to procedural generation at some point, but am wondering if it is practical to have a procedurally generated grid (wall squares possibly same dimensions as the open space squares), or if designing to a thin wall open spaces is better? this decision will effect the amount of work need on the graphics end for uniform vs. irregular walls. EDIT: game will be a elevation maze shooter. levels/maps will be mazes with elevation the player has to negotiate. elevations will have effects on "combat" vision, and movement

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• ASP.NET MVC 3 (C#) Software Architecture

  - by ryanzec

  I am starting on a relatively large and ambitious ASP.NET MVC 3 project and just thinking about the best way to organize my code. The project is basically going to be a general management system that will be capable of supporting any type management system whether it be a blogging system, cms, reservation system, wikis, forums, project management system, etc…, each of them being just a separate 'module'. You can read more about it on my blog posted here : http://www.ryanzec.com/index.php/blog/details/8 (forgive me, the style of the site kinda sucks). For those who don't want to read the long blog post the basic idea is that the core system itself is nothing more than a users system with an admin interface to manage the users system. Then you just add on module as you need them and the module I will be creating is a simple blog post to test it out before I move on to the big module which is a project management system. Now I am just trying to think of the best way to structure this so that it is easy for users to add in there own modules but easy for me to update to core system without worrying about the user modifying the core code. I think the ideal way would be to have a number of core projects that user is specifically told not to modify otherwise the system may become unstable and future updates would not work. When the user wants to add in there own modules, they would just add in a new project (or multiple projects). The thing is I am not sure that it is even possible to use multiple projects all with their own controllers, razor view template, css, javascript, etc... in one web application. Ideally each module would have some of it own razor view templates, css, javascript, image files and also need access to some of the core razor view templates, css, javascript, image files which would is in a separate project. It is possible to have 1 web application run off of controllers, razor view templates, css, javascript, image files that are store in multiple projects? Is there a better was to structure this to allow the user to easily add in module with having to modify the core code?

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• Service Layer - how broad should it be, and should it also be on the local application?

  - by BornToCode

  Background: I need to build a desktop application with some operations (CRUD and more) (=winforms), I need to make another application which will re-use some of the functions of the main application (=webforms). I understood that using service layer is the best approach here. If I understood correctly the service should be calling the function on the BL layer (correct me if I'm wrong) The dilemma: In my main winform UI - should I call the functions from the BL, or from the service? (please explain why) Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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• Expiring timed actions a good idea?

  - by Bart van Heukelom

  We have an online game where players sometimes have to wait a while (say 30 minutes) before a process they intiated completes. This encourages them to come back later. An example of this is growing crops in Farmville or basically any action in the Sims Play4Free. Now, however, there is the idea to let these processes expire, so if the player doesn't 'reap' them in time (e.g. within 4 hours) they are aborted. I'm a bit sceptical about this. How will this make players come back more often? Is not the reward of reaping the process enough for that? Can we expect players to fit their daily schedule around our game, maybe even set the alarm clock at night? Won't this just cause players to give up on starting these processes in the first place? I realise this may be too subjective for this site, so I'll end with a concrete question: Do (m)any other online free-to-play games employ this technique?

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• Should I close database connections after use in PHP?

  - by Sprottenwels

  I wonder if I should close any unnecessary database connection inside of my PHP scripts. I am aware of the fact that database connections are closed implicitly when the block stops executing and 'manually' closing the connections could kinda bloat the codebase with unnecessary code. But shouldn't I do so in order to make by code as readable and as easy understandable as possible, while also preventing several possible issues during run time? Also, if I would do, would it be enough to unset() my database object?

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• Connection Strings, an Overview

  We asked Phil to come up with a simple explanation of connection strings. We somehow weren't expecting a 'quote of the day' for your database, or a C# application to gather data from the internet. However, sometimes the oblique approach is the best, especially when the knowledge comes from hard-won experience by a cynical man.

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• Is there a simple isometric graphical game engine (using vectors?) that could be used for a (multiplayer) crafting/farming game? [closed]

  - by Renier Wijnen

  Possible Duplicate: Good, free isometric game engine? With little game development experience (albeit having graphical skills and some programming knowledge) a group currently working on a game used to explain permaculture through interaction would like to create a simple concept game. Is there a specific engine or set of tools we could used to achieve this? Being able to make it an (online) multiplayer game would be much preferred. Thank you in advance for your input.

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• Best Option for Creating A Small Church Website

  - by Jim

  I've been asked to create a website for a small church. Their prior site was hosted on geocities which is no longer. They are not looking for anything robust, just an informational site with a calendar and maybe a contact form. The church would also like to be able to administer the site with little technical know-how. Cost is also an issue. Given these requirements, something like sites.google.com seems like a good option. However, my main concern is that Sites will suffer the same fate as geocities. It is definitely not a flagship Google product. Are there other good alternatives that fit the requirements?

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• How to store prices that have effective dates?

  - by lal00

  I have a list of products. Each of them is offered by N providers. Each providers quotes us a price for a specific date. That price is effective until that provider decides to set a new price. In that case, the provider will give the new price with a new date. The MySQL table header currently looks like: provider_id, product_id, price, date_price_effective Every other day, we compile a list of products/prices that are effective for the current day. For each product, the list contains a sorted list of the providers that have that particular product. In that way, we can order certain products from whoever happens to offer the best price. To get the effective prices, I have a SQL statement that returns all rows that have date_price_effective >= NOW(). That result set is processed with a ruby script that does the sorting and filtering necessary to obtain a file that looks like this: product_id_1,provider_1,provider_3,provider8,provider_10... product_id_2,provider_3,provider_2,provider1,provider_10... This works fine for our purposes, but I still have an itch that a SQL table is probably not the best way to store this kind of information. I have that feeling that this kind of problema has been solved previously in other more creative ways. Is there a better way to store this information other than in SQL? or, if using SQL, is there a better approach than the one I'm using?

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• How to handle status columns in designing tables

  - by altsyset

  How to handle multiple statuses for a table entry, for example an item table may have an active, inactive, fast moving, and/or batch statuses. And I wanted to handle them in single column with VARCHAR type. Also I might set each of those attributes as a boolean with different columns. But I am not sure what consequences this might lead to. So if you have experienced such situations which one would be the best way to handle it?

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• Designing exceptions for conversion failures

  - by Mr.C64

  Suppose there are some methods to convert from "X" to "Y" and vice versa; the conversion may fail in some cases, and exceptions are used to signal conversion errors in those cases. Which would be the best option for defining exception classes in this context? A single XYConversionException class, with an attribute (e.g. an enum) specifying the direction of the conversion (e.g. ConversionFromXToY, ConversionFromYToX). A XYConversionException class, with two derived classes ConversionFromXToYException and ConversionFromYToXException. ConversionFromXToYException and ConversionFromYToXException classes without a common base class.

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• Help identify the pattern for reacting on updates

  - by Mike

  There's an entity that gets updated from external sources. Update events are at random intervals. And the entity has to be processed once updated. Multiple updates may be multiplexed. In other words there's a need for the most current state of entity to be processed. There's a point of no-return during processing where the current state (and the state is consistent i.e. no partial update is made) of entity is saved somewhere else and processing goes on independently of any arriving updates. Every consequent set of updates has to trigger processing i.e. system should not forget about updates. And for each entity there should be no more than one running processing (before the point of no-return) i.e. the entity state should not be processed more than once. So what I'm looking for is a pattern to cancel current processing before the point of no return or abandon processing results if an update arrives. The main challenge is to minimize race conditions and maintain integrity. The entity sits mainly in database with some files on disk. And the system is in .NET with web-services and message queues. What comes to my mind is a database queue-like table. An arriving update inserts row in that table and the processing is launched. The processing gathers necessary data before the point of no-return and once it reaches this barrier it looks into the queue table and checks whether there're more recent updates for the entity. If there are new updates the processing simply shuts down and its data is discarded. Otherwise the processing data is persisted and it goes beyond the point of no-return. Though it looks like a solution to me it is not quite elegant and I believe this scenario may be supported by some sort of middleware. If I would use message queues for this then there's a need to access the queue API in the point of no-return to check for the existence of new messages. And this approach also lacks elegance. Is there a name for this pattern and an existing solution?

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• Strategy to use two different measurement systems in software

  - by Dennis

  I have an application that needs to accept and output values in both US Custom Units and Metric system. Right now the conversion and input and output is a mess. You can only enter in US system, but you can choose the output to be US or Metric, and the code to do the conversions is everywhere. So I want to organize this and put together some simple rules. So I came up with this: Rules user can enter values in either US or Metric, and User Interface will take care of marking this properly All units internally will be stored as US, since the majority of the system already has most of the data stored like that and depends on this. It shouldn't matter I suppose as long as you don't mix unit. All output will be in US or Metric, depending on user selection/choice/preference. In theory this sounds great and seems like a solution. However, one little problem I came across is this: There is some data stored in code or in the database that already returns data like this: 4 x 13/16" screws, which means "four times screws". I need the to be in either US or Metric. Where exactly do I put the conversion code for doing the conversion for this unit? The above already mixing presentation and data, but the data for the field I need to populate is that whole string. I can certainly split it up into the number 4, the 13/16", and the " x " and the " screws", but the question remains... where do I put the conversion code? Different Locations for Conversion Routines 1) Right now the string is in a class where it's produced. I can put conversion code right into that class and it may be a good solution. Except then, I want to be consistent so I will be putting conversion procedures everywhere in the code at-data-source, or right after reading it from the database. The problem though is I think that my code will have to deal with two systems, all throughout the codebase after this, should I do this. 2) According to the rules, my idea was to put it in the view script, aka last change to modify it before it is shown to the user. And it may be the right thing to do, but then it strikes me it may not always be the best solution. (First, it complicates the view script a tad, second, I need to do more work on the data side to split things up more, or do extra parsing, such as in my case above). 3) Another solution is to do this somewhere in the data prep step before the view, aka somewhere in the middle, before the view, but after the data-source. This strikes me as messy and that could be the reason why my codebase is in such a mess right now. It seems that there is no best solution. What do I do?

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• Could someone explain in detail simplex /or perlin noise?

  - by Ryan Szemplinski

  I am really interested in perlin/simplex noise but I am having a difficult time understanding it. I am not very good at math but I am willing to learn because it interests me greatly. If someone is willing to dedicate there time into this I would be immensely appreciative of this. To be more concise, an explanation of functions and some calculation inside the functions would be nice to understand. Thanks in advance!

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• Designing a simple snake A.I

  - by DillPixel

  I've looked at some stuff online regarding this specific topic, and a lot of the info that I read involved graphs and path finding. I really don't want to get involved in something too complex & out of my level, and also I don't need my snake to be that intelligent (it will be a large board with the snake not growing in size on every munch). How could you structure a simpler AI for the snake that gets the job done relatively well? I would be able to get the snake to move towards the food item correctly, but my issue is that I'm not sure how to deal with the snake colliding with itself. Say the snake has a look ahead, and it finds that its tail is in the way, it could change direction, but what happens next? Any ideas on how to tackle this? Should the snake build an instruction set from every square, or should it think on the go?

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• Whats a good structure to save and retrieve locations of images?

  - by Goot

  I got a java-ee application, where I collect informations about movies. Im my backend I provide data like the name, description, genre and a random uuid. I also got lots of related files, which are stored on a file server. Including some screenshots, the dvd or bluRay cover and video trailers. My current approach is: When saving the files to the fileserver, I retrieve the movies random uuid (which is the primary key btw.). I then rename the files screenshot_[UUID]_1, screenshot_[UUID]_2 ... etc. Now, there are lots of other ways to handle this, like saving all filenames in a database or creating a dir structure on the fileserver for every uuid and, e.g., return all images in the "[uuid]/screenshots" folder via REST. I expect about 30k requests a day, so the service has to be pretty performant. Whats the best way to solve this?

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• Interface extension

  - by user877329

  Suppose that I have an input stream interface, which defines a method for reading data. I also have a seekable interface which defines a method for seeking. A natural way of defining a input file is then to implement both input stream and seekable. I want to construct a data decoder from the input stream interface so I can read data from a file or from another stream. The problem is that I also want to implement seek functionality to the data decoder, since I want to be able to step individual records not raw bytes. This is not possible if I only provide an input stream, which does not have the bytewise seek method. Should I skip the seekable interface and add the seek method to input stream instead and force all streams to at least leave it as a nop.

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• Concurrency pattern of logger in multithreaded application

  - by Dipan Mehta

  The context: We are working on a multi-threaded (Linux-C) application that follows a pipeline model. Each module has a private thread and encapsulated objects which do processing of data; and each stage has a standard form of exchanging data with next unit. The application is free from memory leak and is threadsafe using locks at the point where they exchange data. Total number of threads is about 15- and each thread can have from 1 to 4 objects. Making about 25 - 30 odd objects which all have some critical logging to do. Most discussion I have seen about different levels as in Log4J and it's other translations. The real big questions is about how the overall logging should really happen? One approach is all local logging does fprintf to stderr. The stderr is redirected to some file. This approach is very bad when logs become too big. If all object instantiate their individual loggers - (about 30-40 of them) there will be too many files. And unlike above, one won't have the idea of true order of events. Timestamping is one possibility - but it is still a mess to collate. If there is a single global logger (singleton) pattern - it indirectly blocks so many threads while one is busy putting up logs. This is unacceptable when processing of the threads are heavy. So what should be the ideal way to structure the logging objects? What are some of the best practices in actual large scale applications? I would also love to learn from some of the real designs of large scale applications to get inspirations from!

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• How should I write new code when the old codebase and the environment uses lots of globals in PHP

  - by Nicola Peluchetti

  I'm working in the Wordpress environment which itself heavily relies on globals and the codebase I'm maintaining introduces some more. I want this to change and so I'm trying to think how should I handle this. For the globals our code has introduced I think I will set them as dependencies in the constructor or in getter / setter so that I don't rely on them being globals and then refactor the old codebase little by little so that we have no globals. With Wordpress globals I was thinking to wrap all WP globals inside a Wrapper class and hide them in there. Like this class WpGlobals { public static function getDb() { global $wpdb; return $wpdb; } } Would this be of any help? The idea is that I centralize all globals in one class and do not scatter them through the code, so that if Wordpress kills one of them I need to modify code only in one place. What would you do?

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• Managing accounts on a private website for a real-life community

  - by Smudge

  I'm looking at setting-up a walled-in website for a real-life community of people, and I was wondering if anyone has any experience with managing member accounts for this kind of thing. Some conditions that must be met: This community has a set list of real-life members, each of whom would be eligible for one account on the website. We don't expect or require that they all sign-up. It is purely opt-in, but we anticipate that many of them would be interested in the services we are setting up. Some of the community members emails are known, but some of them have fallen off the grid over the years, so ideally there would be a way for them to get back in touch with us through the public-facing side of the site. (And we'd want to manually verify the identity of anyone who does so). Their names are known, and for similar projects in the past we have assigned usernames derived from their real-life names. This time, however, we are open to other approaches, such as letting them specify their own username or getting rid of usernames entirely. The specific web technology we will use (e.g. Drupal, Joomla, etc) is not really our concern right now -- I am more interested in how this can be approached in the abstract. Our database already includes the full member roster, so we can email many of them generated links to a page where they can create an account. (And internally we can require that these accounts be paired with a known member). Should we have them specify their own usernames, or are we fine letting them use their registered email address to log-in? Are there any paradigms for walled-in community portals that help address security issues if, for example, one of their email accounts is compromised? We don't anticipate attempted break-ins being much of a threat, because nothing about this community is high-profile, but we do want to address security concerns. In addition, we want to make the sign-up process as painless for the members as possible, especially given the fact that we can't just make sign-ups open to anyone. I'm interested to hear your thoughts and suggestions! Thanks!

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• Why don't languages include implication as a logical operator?

  - by Maciej Piechotka

  It might be a strange question, but why there is no implication as a logical operator in many languages (Java, C, C++, Python Haskell - although as last one have user defined operators its trivial to add it)? I find logical implication much clearer to write (particularly in asserts or assert-like expressions) then negation with or: encrypt(buf, key, mode, iv = null) { assert (mode != ECB --> iv != null); assert (mode == ECB || iv != null); assert (implies(mode != ECB, iv != null)); // User-defined function }

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• Preferred lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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