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• Strengthening code with possibly useless exception handling

  - by rdurand

  Is it a good practice to implement useless exception handling, just in case another part of the code is not coded correctly? Basic example A simple one, so I don't loose everybody :). Let's say I'm writing an app that will display a person's information (name, address, etc.), the data being extracted from a database. Let's say I'm the one coding the UI part, and someone else is writing the DB query code. Now imagine that the specifications of your app say that if the person's information is incomplete (let's say, the name is missing in the database), the person coding the query should handle this by returning "NA" for the missing field. What if the query is poorly coded and doesn't handle this case? What if the guy who wrote the query handles you an incomplete result, and when you try to display the informations, everything crashes, because your code isn't prepared to display empty stuff? This example is very basic. I believe most of you will say "it's not your problem, you're not responsible for this crash". But, it's still your part of the code which is crashing. Another example Let's say now I'm the one writing the query. The specifications don't say the same as above, but that the guy writing the "insert" query should make sure all the fields are complete when adding a person to the database to avoid inserting incomplete information. Should I protect my "select" query to make sure I give the UI guy complete informations? The questions What if the specifications don't explicitly say "this guy is the one in charge of handling this situation"? What if a third person implements another query (similar to the first one, but on another DB) and uses your UI code to display it, but doesn't handle this case in his code? Should I do what's necessary to prevent a possible crash, even if I'm not the one supposed to handle the bad case? I'm not looking for an answer like "(s)he's the one responsible for the crash", as I'm not solving a conflict here, I'd like to know, should I protect my code against situations it's not my responsibility to handle? Here, a simple "if empty do something" would suffice. In general, this question tackles redundant exception handling. I'm asking it because when I work alone on a project, I may code 2-3 times a similar exception handling in successive functions, "just in case" I did something wrong and let a bad case come through.

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• When and why you should use void (instead of i.e. bool/int)

  - by Jonas

  I occasionally run into methods where a developer chose to return something which isn't critical to the function. I mean, when looking at the code, it apparently works just as nice as a void and after a moment of thought, I ask "Why?" Does this sound familiar? Sometimes I would agree that most often it is better to return something like a bool or int, rather then just do a void. I'm not sure though, in the big picture, about the pros and cons. Depending on situation, returning an int can make the caller aware of the amount of rows or objects affected by the method (e.g., 5 records saved to MSSQL). If a method like "InsertSomething" returns a boolean, I can have the method designed to return true if success, else false. The caller can choose to act or not on that information. On the other hand, May it lead to a less clear purpose of a method call? Bad coding often forces me to double-check the method content. If it returns something, it tells you that the method is of a type you have to do something with the returned result. Another issue would be, if the method implementation is unknown to you, what did the developer decide to return that isn't function critical? Of course you can comment it. The return value has to be processed, when the processing could be ended at the closing bracket of method. What happens under the hood? Did the called method get false because of a thrown error? Or did it return false due to the evaluated result? What are your experiences with this? How would you act on this?

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• Button postion not changing in View Controller. (Xcode)

  - by theCodeKing

  I have a View controller in xcode 6 (beta 5). I have put 4 buttons in it through the Object library in a .xib. But when i open the app in iOS simulator the buttons are the right y position but not correct x-position()they are on the right edge. No matter where i move them in the xib they only change y-position. I even moved them using the size inspector, but to no avail. How can i actually move them?

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• Number crunching algo for learning multithreading?

  - by Austin Henley

  I have never really implemented anything dealing with threads; my only experience with them is reading about them in my undergrad. So I want to change that by writing a program that does some number crunching, but splits it up into several threads. My first ideas for this hopefully simple multithreaded program were: Beal's Conjecture brute force based on my SO question. Bailey-Borwein-Plouffe formula for calculating Pi. Prime number brute force search As you can see I have an interest in math and thought it would be fun to incorporate it into this, rather than coding something such as a server which wouldn't be nearly as fun! But the 3 ideas don't seem very appealing and I have already done some work on them in the past so I was curious if anyone had any ideas in the same spirit as these 3 that I could implement?

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• Should my program "be lenient" in what it accepts and "discard faulty input silently"?

  - by romkyns

  I was under the impression that by now everyone agrees this maxim was a mistake. But I recently saw this answer which has a "be lenient" comment upvoted 137 times (as of today). In my opinion, the leniency in what browsers accept was the direct cause of the utter mess that HTML and some other web standards were a few years ago, and have only recently begun to properly crystallize out of that mess. The way I see it, being lenient in what you accept will lead to this. The second part of the maxim is "discard faulty input silently, without returning an error message unless this is required by the specification", and this feels borderline offensive. Any programmer who has banged their head on the wall when something fails silently will know what I mean. So, am I completely wrong about this? Should my program be lenient in what it accepts and swallow errors silently? Or am I mis-interpreting what this is supposed to mean? Taken to the extreme, if Excel followed this maxim and I gave it an exe file to open, it would just show a blank spreadsheet without even mentioning that anything went wrong. Is this really a good principle to follow?

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• What should be allowed inside getters and setters?

  - by Botond Balázs

  I got into an interesting internet argument about getter and setter methods and encapsulation. Someone said that all they should do is an assignment (setters) or a variable access (getters) to keep them "pure" and ensure encapsulation. Am I right that this would completely defeat the purpose of having getters and setters in the first place and validation and other logic (without strange side-effects of course) should be allowed? When should validation happen? When setting the value, inside the setter (to protect the object from ever entering an invalid state - my opinion) Before setting the value, outside the setter Inside the object, before each time the value is used Is a setter allowed to change the value (maybe convert a valid value to some canonical internal representation)?

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• Finding an A* heuristic for a directed graph

  - by Janis Peisenieks

  In a previous question, I asked about finding a route (or path if you will) in a city. That is all dandy. The solution I chose was with the A* algorithm, which really seems to suit my needs. What I find puzzling is heuristic. How do I find one in an environment without constant distance between 2 nodes? Meaning, not every 2 nodes have the same distance between them. What I have is nodes (junctures), streets with weight (which may also be one-way), a start/finish node (since the start and end is always in the same place) and a goal node. In an ordinary case, I would just use the same way I got to goal to go back, but since one of the streets could have been a one-way, that may not be possible. The main question How do I find a heuristic in a directed graph?

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• How to learn the math behind the code?

  - by Solomon Wise

  I am a 12 year old who has recently gotten into programming. (Although I know that the number of books you have read does not determine your programming competency or ability, just to paint a "map" of where I am in terms of the content I know...) I've finished the books: Python 3 For Absolute Beginners Pro Python Python Standard Library by Example Beautiful Code Agile Web Development With Rails and am about halfway into Programming Ruby. I have written many small programs (One that finds which files have been updated and deleted in a directory, one that compares multiple players' fantasy baseball value, and some text based games, and many more). Obviously, as I'm not some sort of child prodigy, I can't take a formal Computer Science course until high school. I really want to learn computer science to increase my knowledge about the code, and the how the code runs. I've really become interested in the math part after reading the source code for Python's random module. Is there a place where I can learn CS, or programming math online for free, at a level that would be at least partially understandable to a person my age?

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• Does a prose to code compiler exist?

  - by Raynos

  I have seen some horrible code in my time including people virtually duplicating the code in comments // add 4 to x x+=4; // for each i in 0 to 9 for (int i = 0; i < 10; i++) { // multiply x by i x *= i; } Taking this concept further, I'm curious whether prose to code compilers exist. Is there a valid use case for English prose to code? Do compilers exist that do this? The distinction between this and auto generated code, is that auto generated code is generally always a subset of a project. Can we have complete projects auto generated from english prose? I realise that this might overlap with the concept of declarative languages.

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• How does one handle an incorrect resource file?

  - by AedonEtLIRA

  I'm starting the parser that will handle one of the key features of my app and realizing exactly who easy it would be for me to screw up a resource file that is provided to the application. For example, a simple resource that I provide to my app is a JSON file that contains an entity layout (name, fascia, location etc...). It would be easy for me to leave out the name of the entity or misspell the JSON key. Obviously catastrophic failures during parsing are to be handled in a try/catch, but how would subtle failures (such as a dyslexic spelling of name) be handled?

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• How are Implicit-Heap dynamic Storage Binding and Dynamic type binding similar?

  - by Appy

  "Concepts of Programming languages" by Robert Sebesta says - Implicit Heap-Dynamic Storage Binding: Implicit Heap-Dynamic variables are bound to heap storage only when they are assigned values. It is similar to dynamic type binding. Can anyone explain the similarity with suitable examples. I understand the meaning of both the phrases, but I am an amateur when it comes to in-depth details.

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• Library to fake intermittent failures according to tester-defined policy?

  - by crosstalk

  I'm looking for a library that I can use to help mock a program component that works only intermittently - usually, it works fine, but sometimes it fails. For example, suppose I need to read data from a file, and my program has to avoid crashing or hanging when a read fails due to a disk head crash. I'd like to model that by having a mock data reader function that returns mock data 90% of the time, but hangs or returns garbage otherwise. Or, if I'm stress-testing my full program, I could turn on debugging code in my real data reader module to make it return real data 90% of the time and hang otherwise. Now, obviously, in this particular example I could just code up my mock manually to test against a random() routine. However, I was looking for a system that allows implementing any failure policy I want, including: Fail randomly 10% of the time Succeed 10 times, fail 4 times, repeat Fail semi-randomly, such that one failure tends to be followed by a burst of more failures Any policy the tester wants to define Furthermore, I'd like to be able to change the failure policy at runtime, using either code internal to the program under test, or external knobs or switches (though the latter can be implemented with the former). In pig-Java, I'd envision a FailureFaker interface like so: interface FailureFaker { /** Return true if and only if the mocked operation succeeded. Implementors should override this method with versions consistent with their failure policy. */ public boolean attempt(); } And each failure policy would be a class implementing FailureFaker; for example there would be a PatternFailureFaker that would succeed N times, then fail M times, then repeat, and a AlwaysFailFailureFaker that I'd use temporarily when I need to simulate, say, someone removing the external hard drive my data was on. The policy could then be used (and changed) in my mock object code like so: class MyMockComponent { FailureFaker faker; public void doSomething() { if (faker.attempt()) { // ... } else { throw new RuntimeException(); } } void setFailurePolicy (FailureFaker policy) { this.faker = policy; } } Now, this seems like something that would be part of a mocking library, so I wouldn't be surprised if it's been done before. (In fact, I got the idea from Steve Maguire's Writing Solid Code, where he discusses this exact idea on pages 228-231, saying that such facilities were common in Microsoft code of that early-90's era.) However, I'm only familiar with EasyMock and jMockit for Java, and neither AFAIK have this function, or something similar with different syntax. Hence, the question: Do such libraries as I've described above exist? If they do, where have you found them useful? If you haven't found them useful, why not?

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• Why Use !boolean_variable Over boolean_variable == false

  - by ell

  A comment on this question: Calling A Method that returns a boolean value inside a conditional statement says that you should use !boolean instead of boolean == false when testing conditions. Why? To me boolean == false is much more natural in English and is more explicit. I apologise if this is just a matter of style, but I was wondering if there was some other reason for this preference of !boolean?

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• Preffered 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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• Rel = translation

  - by Tom Gullen

  I can't find much online about rel="translation" We have tutorials and manual entries which we are going to get users to translate. If the original page in English is: http://www.scirra.com/tutorial/start And there are two translations: http://www.scirra.com/tutorial/es/start (spanish) http://www.scirra.com/tutorial/de/start (german) How would I correctly link all these up? I'm aware at the top of the page I would need to specify the correct IS639-1 code: <html lang="de"> But I'm more interested in letting Google know they are not duplicates but are translated.

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• Open source framework quality [closed]

  - by Jonas Byström

  It's not hard to find snippets, components or tools/toolkits in the open source world which holds the quality bar really high. Myself I use git, python, linux, gcc, bash and a whole range of others on a daily basis, and I love them. But when it comes to bigger frameworks, which are intended for facilitating larger tasks of an application without much interference, I'm not as enthusiastic. I've tried a few commercial frameworks (game engines), which were okay, but all big open source frameworks which I've used myself, or which I have seen used in applications were decidedly worse than the commercial equivalent. But I'm not sure if my experience was typical. Where have bigger open source frameworks for facilitating larger tasks of an application been able to equal or exceed commercial frameworks, and how were they better?

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• Overloading interface buttons, what are the best practices?

  - by XMLforDummies

  Imagine you'll have always a button labeled "Continue" in the same position in your app's GUI. Would you rather make a single button instance that takes different actions depending on the current state? private State currentState = State.Step1; private ContinueButton_Click() { switch(currentState) { case State.Step1: DoThis(); currentState = State.Step2; break; case State.Step2: DoThat(); break; } } Or would you rather have something like this? public Form() { this.ContinueStep2Button.Visible = false; } private ContinueStep1Button_Click() { DoThis(); this.ContinueStep1Button.Visible = false; this.ContinueStep2Button.Visible = true; } private ContinueStep2Button_Click() { DoThat(); }

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• String patterns that can be used to filter and group files

  - by Louis Rhys

  One of our application filters files in certain directory, extract some data from it and export a document from the extracted data. The algorithm for extracting the data depends on the file, and so far we use regex to select the algorithm to be used, for example .*\.txt will be processed by algorithm A, foo[0-5]\.xml will be processed by algo B, etc. However now we need some files to be processed together. For example, in one case we need two files, foo.*\.xml and bar.*\.xml. Part of the information to be extracted exist in the foo file, and the other part in the bar file. Moreover, we need to make sure the wild card is compatible. For example, if there are 6 files foo1.xml foo23.xml bar1.xml bar9.xml bar23.xml foo4.xml I would expect foo1 and bar1 to be identified as a group, and foo23 and bar23 as another group. bar9 and foo4 has no pair, so they will not be treated. Now, since the filter is configured by user, we need to have a pattern that can express the above requirement. I don't think you can express meaning like above in standard regex. (foo|bar).*\.xml will match all 6 file above and we can't identify which file is paired for a particular file. Is there any standard pattern that can express it? Or any idea how to modify regex to support this, that can be implemented easily?

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• Programming is easy, Designing is hard

  - by Rachel

  I work as Programmer and I feel if design documents are properly in place and requirements are clearly specified than programming is not that difficult but when I think in terms of Designing a Software than it gives chills to me and I think its a very difficult part. I want to develop my Design Skills so, How should I go about it ? Are there any books, blogs, websites or other approaches that SO community can suggest ? Update: By Design I meant Design of overall Application or particular problem at hand and not UI Design.

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• Data migration - dangerous or essential?

  - by MRalwasser

  The software development department of my company is facing with the problem that data migrations are considered as potentially dangerous, especially for my managers. The background is that our customers are using a large amount of data with poor quality. The reasons for this is only partially related to our software quality, but rather to the history of the data: Most of them have been migrated from predecessor systems, some bugs caused (mostly business) inconsistencies in the data records or misentries by accident on the customer's side (which our software allowed by error). The most important counter-arguments from my managers are that faulty data may turn into even worse data, the data troubles may awake some managers at the customer and some processes on the customer's side may not work anymore because their processes somewhat adapted to our system. Personally, I consider data migrations as an integral part of the software development and that data migration can been seen to data what refactoring is to code. I think that data migration is an essential for creating software that evolves. Without it, we would have to create painful software which somewhat works around a bad data structure. I am asking you: What are your thoughts to data migration, especially for the real life cases and not only from a developer's perspecticve? Do you have any arguments against my managers opinions? How does your company deal with data migrations and the difficulties caused by them? Any other interesting thoughts which belongs to this topics?

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• Pattern for a class that does only one thing

  - by Heinzi

  Let's say I have a procedure that does stuff: void doStuff(initalParams) { ... } Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class: class StuffDoer { private someInternalState; public Start(initalParams) { ... } // some private helper procedures here ... } And then I call it like this: new StuffDoer().Start(initialParams); or like this: new StuffDoer(initialParams).Start(); And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method: public static DoStuff(initalParams) { new StuffDoer().Start(initialParams); } But then I'd have a class whose external interface consists of only one static method, which also feels weird. Hence my question: Is there a well-established pattern for this type of classes that have only one entry point and have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?

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• Simplifying C++11 optimal parameter passing when a copy is needed

  - by Mr.C64

  It seems to me that in C++11 lots of attention was made to simplify returning values from functions and methods, i.e.: with move semantics it's possible to simply return heavy-to-copy but cheap-to-move values (while in C++98/03 the general guideline was to use output parameters via non-const references or pointers), e.g.: // C++11 style vector<string> MakeAVeryBigStringList(); // C++98/03 style void MakeAVeryBigStringList(vector<string>& result); On the other side, it seems to me that more work should be done on input parameter passing, in particular when a copy of an input parameter is needed, e.g. in constructors and setters. My understanding is that the best technique in this case is to use templates and std::forward<>, e.g. (following the pattern of this answer on C++11 optimal parameter passing): class Person { std::string m_name; public: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> explicit Person(T&& name) : m_name(std::forward<T>(name)) { } ... }; A similar code could be written for setters. Frankly, this code seems boilerplate and complex, and doesn't scale up well when there are more parameters (e.g. if a surname attribute is added to the above class). Would it be possible to add a new feature to C++11 to simplify code like this (just like lambdas simplify C++98/03 code with functors in several cases)? I was thinking of a syntax with some special character, like @ (since introducing a &&& in addition to && would be too much typing :) e.g.: class Person { std::string m_name; public: /* Simplified syntax to produce boilerplate code like this: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> */ explicit Person(std::string@ name) : m_name(name) // implicit std::forward as well { } ... }; This would be very convenient also for more complex cases involving more parameters, e.g. Person(std::string@ name, std::string@ surname) : m_name(name), m_surname(surname) { } Would it be possible to add a simplified convenient syntax like this in C++? What would be the downsides of such a syntax?

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• Comparison of languages by usage type?

  - by Tom

  Does anyone know of a good place to go find comparisons of programming languages by the intended platform/usage? Basically, what I want to know, is of the more popular languages, which ones are meant for high level application development, low level system development, mobile development, web, etc. If there's a good listing out there already, I'm not finding it so far. Does anyone know of a place that would have this? Thanks.

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• Strategy for backwards compatibility of persistent storage

  - by Baqueta

  In my experience, trying to ensure that new versions of an application retain compatibility with data storage from previous versions can often be a painful process. What I currently do is to save a version number for each 'unit' of data (be it a file, database row/table, or whatever) and ensure that the version number gets updated each time the data changes in some way. I also create methods to convert from v1 to v2, v2 to v3, and so on. That way, if I'm at v7 and I encounter a v3 file, I can do v3-v4-v5-v6-v7. So far this approach seems to be working out well, but I haven't had to make use of it extensively yet so there may be unforseen problems. I'm also concerned that if the objects I'm loading change significantly, I'll either have to keep around old versions of the classes or face updating all my conversion methods to handle the new class definition. Is my approach sound? Are there other/better approaches I could be using? Are there any design patterns applicable to this problem?

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• What do you call "X <= $foo <= Y" comparison?

  - by Jakob

  While writing a Perl statement like if ( $foo >= X && $foo <= Y ) yet again, I wondered why many programming languages do not support the more comfortable form if ( X <= $foo <= Y ) and what this is called. I came up with "3-legged comparison" but no results when searching for it. By the way there is also the "element-of-set" form if ( $foo in X..Y ) which I only consider more readable when provided via a short keyword. Is there a term for X <= $foo <= Y comparison? Which languages support it?

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