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• Storing data for use on Android and Windows Applications

  - by Andy Mepham

  I posted this last night on StackOverflow and was advised to move it over to StackExchange, thank you for taking a moment to look at my question. I'm developing a project proposal for my final year project at University and as I aim to use programming languages I am currently not too familiar with I'm looking for some guidance - I can't include details of my project but hopefully you will understand what I'm after. I'm going to be creating an Android application (in Java) and a Windows Application (in C#) that will ideally access, query and update a remotely hosted Database or set of XML files (this would most likely be over the Internet). I've done some looking around the internet and SQLite seems like a safe-bet for cross-platform manipulation of the database; however I would like to keep the system as lightweight as possible and I'm wondering whether XML files may provide a better alternative? Anyone out there that has experience using SQLite and/or remotely hosted XML for the purposes of Android and/or C# development that could point me in the right direction? If there is an alternative solution other than those I have mentioned I would be interested to hear about them too. Thank you for taking the time to read my question. Edit: The purpose of this application is for a small scale business, the data source would not need to be updated by more than one source but may be view from multiple sources (i.e. through multiple phones and a desktop PC). The database wouldn't be updating masses of data at a time (most likely single rows of a few tables at the most).

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• How is a "Software Developer" different from a "Software Consultant"? What makes a consultant?

  - by Kumar

  I have seen a lot of people claiming themselves to be a "software consultant". These consultants do what a normal software developer does, write code, estimate tasks, fix bugs and attend meetings etc. The only difference being the financials, consultants end up earning more. Then how is a software developer different from a "consultant"? In addition to the main question, I would like to know how can a software developer become a consultant? Are there any specific guidelines for a consultant? Do they need to amass certifications and write up research papers? Please do not confuse the software consultant with a management consultant. Software consultants I have seen are not managers.

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• How do we keep dependent data structures up to date?

  - by Geo

  Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

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• Web services, Java EE, Spring, DB integration project ideas - maybe data mining related?

  - by saral jain

  I am a graduate Computer Science student (Data Mining and Machine Learning) and have good exposure to core Java (3 years). I have read up on a bunch of stuff on the following topics: Design patterns, Java EE Web services (SOAP and REST), Spring, and Hibernate Java Concurrency - advanced features like Task and Executors. I would now like to do a project combining this stuff -- over my free time of course -- to get a better understanding of these things and to kind of make an end to end software (to learn the best design principles etc + SVN, maven). Any good project ideas would be really appreciated. I just want to build this stuff to learn, so I don't really mind re-inventing the wheel. Also, anything related to data mining would be an added bonus as it fits with my research but is absolutely not necessary since this project is more to learn to do large scale software development.

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• MATLAB: Best fitness vs mean fitness, initial range

  - by Sa Ta

  Based on the example of Rastrigin's function. At the plot function, if I chose 'best fitness', on the same graph 'mean fitness' will also be plotted. I understand well about 'best fitness' whereby it plots the best function value in each generation versus iteration number. It will reach value zero after some times. I don't understand about 'mean fitness'in the graph plotted. What do those 'mean fitness' values mean? How does the 'mean fitness' graph help to understand Rastrigin's function? What are the meaning of the term initial population, initial score and initial range? I wish to have a better understanding of these terms. The default value for initial range is [0,1]. Does it mean that 0 is the lower bound (lb) and 1 is the upper bound (ub)? Do these values interfere with the lb and ub values I set in the constraints? I try to better understand about lb and ub. If my lb is 0 and ub is 5, does it mean that my final point values will be within 0 and 5? If I know the lb and ub for my problem is between 0 and 5, do I just set the initial range as [0,5] at all times and may I assume that this is the best option for initial range, and I need not try it with any other values?

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• Educational, well-written FOSS projects to read, study or discuss

  - by Godot

  Before you say it: yes, this "question" has been asked other times. However, I could not fine many of such questions and not that easily, and those I found had similar results. What I'm trying to say that there are no comprehensive lists of well written Open Source projects, so I decided to set some requirements for the entries (one or possibly more): Idiomatic use of the language in which they are written The project should be lightweight. Not as in "a few kbs", as in "clean" and possibly following the UNIX philosophy, making an efficient use of resources and performing its duty and nothing more. No code bloat, most importantly. Projects like Firefox and GNOME wouldn't qualify, for example. Minimal reliance on external, non-standard libraries, with exceptions for some common FOSS libraries (curses, Xlib, OpenGL and possibly "usual suspects" like gtk+, webkit and Boost). Reliance on well-written libraries is welcome. No reliance on proprietary software - for obvious reasons (programs that rely on XNA, DirectX, Cocoa and similar, for example). Well-documented code is welcome. Include link to web interfaces to their repositories if possible. Here are some sample projects that often pop up in these threads: Operating Systems Plan 9 from Bell Labs: More or less, the official "sequel" to UNIX. Written in C by the same people who invented C! NetBSD: The most portable BSD implementation, written in C and also a good example of portable and organized code. Network and Databases Sqlite: Extremely lightweight and extremely efficient, one of the best pieces of C software I've seen. Count the lines yourself! Lighttpd: A small but pretty reliable web server written in C. Programming languages and VMs Lua: extremely lightweight multi-paradigm programming language. Written in C. Tiny C Compiler: Really tiny C compiler. Not really comparable to GCC or Clang but does its job. PyPy: A Python implementation written in Python. Pharo: OK, I admit it, I'm not really a Smalltalk expert but Pharo is a fork of Squeak and looked rather interesting. Stackless Python - An implementation of Python that doesn't rely on the C call stack - written in C (with some parts in Python) Games and 3D: Angband: One of the most accessible roguelike codebases around here, written in C. Ogre3D: Cross-platform 3D engine. Gets bloated if you don't skip the platform-specific implementation code, otherwise is a pretty solid example of good C++ OO. Simon Tatham's Portable Puzzle Collection: Title says it all. Other - dwm: Lightweight window manager. Written in C. Emulation and Reverse Engineering - Bochs: x86 emulator, written in C++ and tiny enough. - MAME: If you want to see C at one of its lowest levels, MAME is for you. May not be as clean as the other projects but it can teach you A LOT. Before you ask: I didn't mention Linux because it has become quite bloated in the last few years, Linus has also confirmed it. Nonetheless, it'd be a great educational read the same, even if for other reasons. Same for GCC. Feel free to edit or wikify my post. I hope you won't lock my question, I'm only trying to organize a little community effort for the good of all those people who want to enhance their coding skills.

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• Use of Service Bus in a Pub-Sub Engine

  - by JoseK

  In one of our projects, we've built a Publisher - Subscriber Engine on Oracle Service Bus. The functionality being a series of events are published and subscribers (JMS queues) receive these whenever a new event is published. We are facing some technical issues now, performance-wise and hence an architectural review is underway. Now for my questions: Architecturally the ESB has to publish events into a DB and read from the DB which users wish to be notified, then push the event onto their respective queues. There is a high amount of DB interaction and the question is whether ESB should be having such high amount of interaction with the DB in the first place? Or should there have been some alternate component responsible for doing this. Alternately is there any non-DB approach in which we can store the events and subscribers? Where else can this application data be held within the ESB context?

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• Command line options style - POSIX or what?

  - by maaartinus

  Somewhere I saw a rant against java/javac allegedly using a mix of Windows and Unix style like java -classpath ... -ea ... Something IMHO, it is no mix, it's just like find works as well, isn't it? AFAIK, according to POSIX, the syntax should be like java --classpath ... --ea ... Something and -abcdef would mean specifying 6 short options at once. I wonder which version leads in general to less typing and less errors. I'm writing a small utility in Java and in no case I'm going to use Windows style /a /b since I'm interested primarily in Unix. What style should I choose?

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• session management: verifying a user's log-in state

  - by good_computer

  I am storing sessions in my database. Everytime a user logs in, I create a new row corresponding to the new session, generate a new session id and send it as a cookie to the browser. My session data looks something like this: { 'user_id': 1234 'user_name': 'Sam' ... } When a request comes, I check whether a cookie with a session id is sent. If it is, I fetch session data from my database (or memcache) corresponding to that session id. When the user logs out, I remove the session data from my database (and memcache), and delete the cookie from the user's browser too. Notice that in my session data, I don't have something like logged_in: true. This is because if I find a session record in the database (or memcache) I deduce that the user is logged in, and if there is no session record found, the user is not logged in. My question is: is this the right approach? Should I have a logged_in key in my session data? Is there any possibility that a session record may be present on the server where the corresponding user is actually NOT logged in? Are there any security implications in having or not having such a key?

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• How is this number calculated?

  - by Hamid

  I have numbers; A == 0x20000000 B == 18 C == (B/10) D == 0x20000004 == (A + C) A and D are in hex, but I'm not sure what the assumed numeric bases of the others are (although I'd assume base 10 since they don't explicitly state a base. It may or may not be relevant but I'm dealing with memory addresses, A and D are pointers. The part I'm failing to understand is how 18/10 gives me 0x4. Edit: Code for clarity: *address1 (pointer is to address: 0x20000000) printf("Test1: %p\n", address1); printf("Test2: %p\n", address1+(18/10)); printf("Test3: %p\n", address1+(21/10)); Output: Test1: 0x20000000 Test2: 0x20000004 Test3: 0x20000008

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• I would like to know what kind of tools I should be looking for web development.

  - by user646636

  I would like to know what kind of tools I should be looking for web development. I have learned the basics of HTML/CSS/PHP/JS/phpmyadmin Now, I was looking to a write a website for purchasing and selling products for clients and sellers. I was wondering what other languages I would need to learn and also what kinda development tools I should use. Also, what would be the best type of language to write a website like this. I have heard that I should be using python for this type of web development. Do you guys have any suggestion as to what I should be looking at? And Also I would like to know if I should be setting up my own database or should I be using something like MySQL. I'm looking for languages that would have low maintenance cost in the long run. Thanks

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• Release build vs nightly build

  - by Tuomas Hietanen

  Hi! A typical solution is to have a CI (Continuous Integration) build running on a build server: It will analyze the source code, make build (in debug) and run tests, measure test coverage, etc. Now, another build type usually known is "Nightly build": do slow stuff like create code documents, make a setup package, deploy to test environment, and run automatic (smoke or acceptance) tests against the test environment, etc. Now, the question: Is it better to have a third separate "Release build" as release build? Or do "Nightly build" in release mode and use it as a release? What are you using in your company? (The release build should also add some kind of tag to source control of potential product version.)

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• junior / professional / senior categorization

  - by oozoo

  Hey guys, is it just me or is the categorization of developer levels highly subjective? I get the feeling that every company tries to hire experienced developers as juniors because they don't know $technology. For example my own career: I switched technologies a couple of times, while sticking to java as a programming language. For example I first worked for 3 years using JavaSE technologies, the next company I worked for hired me as junior because I didn't have JavaEE experience - while still selling me as professional level to customers (I work in consulting). The next company hired me again as junior because I didn't have SAP experience - they mostly work with SAP Java technologies which is definitely a niche. Still, they are selling all their technology consultants for exactly the same rate while paying them significantly different wages. Now when switching jobs again I feel like this whole thing is going to start all over again because I don't have Spring experience or Oracle knowledge. tl;dr = is my observation totally off base that companies are just using these categorizations as means to keep down wages?

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• Best Java Book(s) for an Experienced Developer

  - by Steven Elliott Jr

  I have been a .NET developer now for about the past 5/6 years give or take. I have never done any professional Java development and the last time I really touched it was probably back in college. I have been toying with the Scala language a little bit but nothing serious. Recently, I've been offered an opportunity to do some pretty cool work, but using Java instead of .NET. I think I can get by alright with my current skill set, meaning I already know how to program well and am familiar with languages such as C# and C++, etc. So, the syntax and all that language stuff are really not a problem. What I need is a really good reference book and a book about how to think in Java. Each language/Framework/Stack tries to address things a certain way and I'm sure Java is no different. What are some great Java books that you simply can't live without? Are there any books that talk about the most important parts of Java that must be understood before all else? As a side note, I will be doing mostly Java web development. Not really 100% on what types of stuff they are using for persistence, framework, server, etc. Thanks again for the consideration.

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• responsibility for storage

  - by Stefano Borini

  A colleague and I were brainstorming about where to put the responsibility of an object to store itself on the disk in our own file format. There are basically two choices: object.store(file) fileformatWriter.store(object) The first one gives the responsibility of serialization on the disk to the object itself. This is similar to the approach used by python pickle. The second groups the representation responsibility on a file format writer object. The data object is just a plain data container (eventually with additional methods not relevant for storage). We agreed on the second methodology, because it centralizes the writing logic from generic data. We also have cases of objects implementing complex logic that need to store info while the logic is in progress. For these cases, the fileformatwriter object can be passed and used as a delegate, calling storage operations on it. With the first pattern, the complex logic object would instead accept the raw file, and implement the writing logic itself. The first method, however, has the advantage that the object knows how to write and read itself from any file containing it, which may also be convenient. I would like to hear your opinion before starting a rather complex refactoring.

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• How to create an auto-grader in and for Python

  - by recluze

  I'm trying to create an auto-grader for one of my beginning programming courses for python. From my online search, I've come to know that it is effectively a unit test framework that tests the student's code rather than production code but I'm not really sure how to structure the flow of the program. Can anyone please provide a strategy for submission of code by students and automating the whole process of marking? For instance, how would the student code be submitted and then stored/structured on disk, how would the grades be stored/reported? I'm only looking for a broad strategy and will try on my own to fill in the blanks. (I asked this on stockoverflow.com initially but it's considered as off-topic and I was suggested to ask here.)

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• How to have a maintainable and manageable Javascript code base

  - by dade

  I am starting a new job soon as a frontend developer. The App I would be working on is 100% Javascript on the client side. all the server returns is an index page that loads all the Javascript files needed by the app. Now here is the problem: The whole of the application is built around having functions wrapped to different namespaces. And from what I see, a simple function like rendering the HTML of a page can be accomplished by having a call to 2 or more functions across different namespace... My initial thought was "this does not feel like the perfect solution" and I can just envisage a lot of issues with maintaining the code and extending it down the line. Now I would soon start working on taking the project forward and would like to have suggestions on good case practices when it comes to writing and managing a relatively large amount of javascript code.

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• Algorithm for tracking progress of controller method running in background

  - by SilentAssassin

  I am using Codeigniter framework for PHP on Windows platform. My problem is I am trying to track progress of a controller method running in background. The controller extracts data from the database(MySQL) then does some processing and then stores the results again in the database. The complete aforesaid process can be considered as a single task. A new task can be assigned while another task is running. The newly assigned task will be added in a queue. So if I can track progress of the controller, I can show status for each of these tasks. Like I can show "Pending" status for tasks in the queue, "In Progress" for tasks running and "Done" for tasks that are completed. Main Issue: Now first thing I need to find is an algorithm to track the progress of how much amount of execution the controller method has completed and that means tracking how much amount of method has completed execution. For instance, this PHP script tracks progress of array being counted. Here the current state and state after total execution are known so it is possible to track its progress. But I am not able to devise anything analogous to it in my case. Maybe what I am trying to achieve is programmtically not possible. If its not possible then suggest me a workaround or a completely new approach. If some details are pending you can mention them. Sorry for my ignorance this is my first post here. I welcome you to point out my mistakes. EDIT: Database outline: The URL(s) and keyword(s) are first entered by user which are stored in a database table called link_master and keyword_master respectively. Then keywords are extracted from all the links present in this table and compared with keywords entered by user and their frequency is calculated which is the final result. And the results are stored in another table called link_result. Now sub-links are extracted from the domain links and stored in a table called sub_link_master. Now again the keywords are extracted from these sub-links and the corresponding results are stored in a table called sub_link_result. The number of records cannot be defined beforehand as the number of links on any web page can be different. Only the cardinality of *link_result* table can be known which will be equal to multiplication of number of keyword(s) and URL(s) . I insert multiple records at a time using this resource. Controller outline: The controller extracts keywords from a web page and also extracts keywords from all the links present on that page. There is a method called crawlLink. I used Rolling Curl to extract keywords and web page content. It has callback function which I used for extracting keywords alongwith generating results and extracting valid sub-links. There is a insertResult method which stores results for links and sub-links in the respective tables. Yes, the processing depends on the number of records. The more the number of records, the more time it takes to execute: Consider this scenario: Number of Domain Links = 1 Number of Keywords = 3 Number of Domain Links Result generated = 3 (3 x 1 as described in the question) Number of Sub Links generated = 41 Number of Sub Links Result = 117 (41 x 3 = 123 but some links are not valid or searchable) Approximate time taken for above process to complete = 55 seconds. The above result is for a single link. I want to track the progress of the above results getting stored in database. When all results are stored, the task is complete. If results are getting stored, the task is In Progress. I am not clear how can I track this progress.

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• Architecture- Tracking lead origin when data is submitted by a server

  - by Kevin

  I'm looking for some assistance in determining the least complex strategy for tracking leads on an affiliate's website. The idea is to make the affiliate's integration with my application as easy as possible. I've run into theoretical barriers, so i'm here to explore other options. Application Overview: This is a lead aggregation / distribution platform. We will be focusing on the affiliate portion of this website. Essentially affiliates sign up, enter in marketing campaigns and sell us their conversions. Problem to be solved: We want to track a lead's origin and other events on the affiliate site. We want to know what pages, ads, and forms they viewed before they converted. This can easily be solved with pixel tracking. Very straightforward. Theoretical Issues: I thought I would ask affiliates to place the pixel where I could log impressions and set a third party cookie when the pixel is first called. Then I could associate future impressions with this cookie. The problem is that when the visitor converts on the affiliate's site and I receive their information via HTTP POST from the Affiliate's server I wouldn't be able to access the cookie and associate it with the lead record unless the lead lands on my processor via a redirect and is then redirected back to the affiliate's landing page. I don't want to force the affiliates to submit their forms directly to my tracking site, so allowing them to make an HTTP POST from their server side form processor would be ideal. I've considered writing JavaScript to set a First Party cookie but this seems to make things more complicated for the affiliate. I also considered having the affiliate submit the lead's data via a conversion pixel. This seems to be the most ideal scenario so far as almost all pixels are as easy as copy/paste. The only complication comes from the conversion pixel- which would submit all of the lead information and the request would come from the visitor's machine so I could access my third party cookie.

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• Why isn't DSM for unstructured memory done today?

  - by sinned

  Ages ago, Djikstra invented IPC through mutexes which then somehow led to shared memory (SHM) in multics (which afaik had the necessary mmap first). Then computer networks came up and DSM (distributed SHM) was invented for IPC between computers. So DSM is basically a not prestructured memory region (like a SHM) that magically get's synchronized between computers without the applications programmer taking action. Implementations include Treadmarks (inofficially dead now) and CRL. But then someone thought this is not the right way to do it and invented Linda & tuplespaces. Current implementations include JavaSpaces and GigaSpaces. Here, you have to structure your data into tuples. Other ways to achieve similar effects may be the use of a relational database or a key-value-store like RIAK. Although someone might argue, I don't consider them as DSM since there is no coherent memory region where you can put data structures in as you like but have to structure your data which can be hard if it is continuous and administration like locking can not be done for hard coded parts (=tuples, ...). Why is there no DSM implementation today or am I just unable to find one?

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• Good resources for language design

  - by Aaron Digulla

  There are lots of books about good web design, UI design, etc. With the advent of Xtext, it's very simple to write your own language. What are good books and resources about language design? I'm not looking for a book about compiler building (like the dragon book) but something that answers: How to create a grammar that is forgiving (like adding optional trailing commas)? Which grammar patterns cause problems for users of a language? How create a compact grammar without introducing ambiguities

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• What are the relative merits for implementing an Erlang-style "Continuation" pattern in C#

  - by JoeGeeky

  What are the relative merits (or demerits) for implementing an Erlang-style "Continuation" pattern in C#. I'm working on a project that has a large number of Lowest priority threads and I'm wondering if my approach may be all wrong. It would seem there is a reasonable upper limit to the number of long-running threads that any one Process 'should' spawn. With that said, I'm not sure what would signal the tipping-point for too many thread or when alternate patterns such as "Continuation" would be more suitable. In this case, many of the threads do a small amount of work and then sleep until woken to go again (Ex. Heartbeat, purge caches, etc...). This continues for the life of the Process.

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• Using my own code in freelance projects.

  - by Witchunter

  I have been into freelance business for more than 2 years. While doing projects for other people, I've build a compilation of common tasks that I implement in projects and put them into code. It's kind of a library with some functions that I can reuse without having to rewrite the same thing dozen times. I'm talking about accessing Access databases, downloading information from FTP and similar stuff. Is this acceptable from a legal point of view? What's the difference in reusing the old code and rewriting it from the scratch (using you own brain again, therefore the exact same logic)? I do not hold any copyright to it, of course, and provide the source code for these classes to my clients.

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• How do you name your personal libraries?

  - by Mehrdad

  I'm pretty bad with naming things. The only name I can every generically come up with is 'helper'. Say, if I have a header file that contains helping functions for manipulating paths, I tend to put it inside my "helper" directory and call it "path-helper.hpp" or something like that. Obviouslly, that's a bad naming convention. :) I want to have a consistent naming scheme for my folder (and namespace) which I can use to always refer to my own headers and libraries, but I have trouble finding names that are easy to type or remember (like boost)... so I end up calling some of them "helper" or "stdext" or whatnot, which isn't a great idea. How do you find names for your libraries that are easy to remember and easy to type, and which aren't too generic (like "helper" or "std" or "stdext" or the like)? Any suggestions on how to go about doing this?

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• null values vs "empty" singleton for optional fields

  - by Uko

  First of all I'm developing a parser for an XML-based format for 3D graphics called XGL. But this question can be applied to any situation when you have fields in your class that are optional i.e. the value of this field can be missing. As I was taking a Scala course on coursera there was an interesting pattern when you create an abstract class with all the methods you need and then create a normal fully functional subclass and an "empty" singleton subclass that always returns false for isEmpty method and throws exceptions for the other ones. So my question is: is it better to just assign null if the optional field's value is missing or make a hierarchy described above and assign it an empty singleton implementation?

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