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• Integration tests - "no exceptions are thrown" approach. Does it make sense?

  - by Andrew Florko

  Sometimes integration tests are rather complex to write or developers have no enough time to check output - does it make sense to write tests that make sure "no exceptions are thrown" only? Such tests provide some input parameters set(s) and doesn't check the result, but only make sure code not failed with exception? May be such tests are not very useful but appropriate in situations when you have no time?

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• Reusability, testability, code complexity reduction and showing-off-ability programming importance

  - by Andrew Florko

  There are lots of programming and architecture patterns. Patterns allow to make code cleaner, reusable, more testable & at last (but not at least) to feel the follower a real cool developer. How do you rank these considerations for you? What does affect you most when you decide to apply pattern? I wonder how many times code reusability (especially for MVP, MVC patterns) was important? For example DAL library often shared between projects (it's reusable) but how often controllers/views (abstracted via interfaces) are reused?

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• MVP pattern. Presenter requires new view instance. Best practice

  - by Andrew Florko

  I try to apply MVP pattern for win.forms application. I have 2 forms: main & child. Main has a button and when you click it - child form should appear. There are 2 views interfaces that forms implement IMainView { event OnClick; ... } IChildView { ... } There are two presenters MainPresenter(IMainView) & ChildPresenter(IChildView) MainPresenter listens to OnClick event and then should create IChildView implementation. MainPresenter { ... MainClicked() { // it's required to create IChildView instance here } } How would you implement such creation typically? Shall IMainView has factory method for IChildView or may be it should be separate Views factory. What would you advise? Or maybe there is some misunderstanding of MVP here? Thank you in advance!

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• Fast, Vectorizable method of taking floating point number modulus of special primes?

  - by caffiend

  Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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• Why do newbie programmers seem to shy away from libraries?

  - by Byron Whitlock

  I've noticed many questions on here from new programmers that can be solved using libraries. When a library is suggested, often times they respond "I don't want to use X library" Is it the learning curve? or ? Just curious!

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• Flow Based Programming

  - by Software Monkey

  I have been doing a little reading on Flow Based Programming over the last few days. There is a wiki which provides further detail. And wikipedia has a good overview on it too. My first thought was, "Great another proponent of lego-land pretend programming" - a concept harking back to the late 80's. But, as I read more, I must admit I have become intrigued. Have you used FBP for a real project? What is your opinion of FBP? Does FBP have a future? In some senses, it seems like the holy grail of reuse that our industry has pursued since the advent of procedural languages.

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• Shortest distance between two line segments

  - by Frank

  I need a function to find the shortest distance between two line segments. A line segment is defined by two endpoints. So for example one of my line segments (AB) would be defined by the two points A (x1,y1) and B (x2,y2) and the other (CD) would be defined by the two points C (x1,y1) and D (x2,y2). Feel free to write the solution in any language you want and I can translate it into javascript. Please keep in mind my geometry skills are pretty rusty. I have already seen http://stochastix.wordpress.com/2008/12/28/distance-between-two-lines/ and I am not sure how to translate this into a function. Thank you so much for help.

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• Which term to use when referring to functional data structures: persistent or immutable?

  - by Bob

  In the context of functional programming which is the correct term to use: persistent or immutable? When I Google "immutable data structures" I get a Wikipedia link to an article on "Persistent data structure" which even goes on to say: such data structures are effectively immutable Which further confuses things for me. Do functional programs rely on persistent data structures or immutable data structures? Or are they always the same thing?

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• How do I generate a random string of up to a certain length?

  - by slavy13

  I would like to generate a random string (or a series of random strings, repetitions allowed) of length between 1 and n characters from some (finite) alphabet. Each string should be equally likely (in other words, the strings should be uniformly distributed). The uniformity requirement means that an algorithm like this doesn't work: alphabet = "abcdefghijklmnopqrstuvwxyz" len = rand(1, n) s = "" for(i = 0; i < len; ++i) s = s + alphabet[rand(0, 25)] (pseudo code, rand(a, b) returns a integer between a and b, inclusively, each integer equally likely) It doesn't work because shorter lengths are as likely as longer ones, meaning it's more likely to generate a shorter string than a longer one, so the result is not uniform.

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• Is there a website to lookup already common code functions?

  - by pinnacler

  I'm sitting here writing a function that I'm positive has been written before, somewhere on earth. It's just too common to have not been attempted, and I'm wondering why I can't just go to a website and search for a function that I can then copy and paste into my project in 2 seconds, instead of wasting my day reinventing the wheel. Sure there are certain libraries you can use, but where do you find these libraries and when they are absent, is there a site like I'm describing?

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• What's the purpose of the empty string?

  - by Max Toro

  To me, as a developer and as a user, I find the empty string ("") useless and the cause of much confusion, it's like saying string == char[] Maybe computers need the empty string, so I'd like to learn why.

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• Find the gender from a name

  - by Ramesh

  Hi guys, I recently confronted with a weird yet interesting question. The questions is as follows: Need to write a program which can give the gender as output based on the name. Example: INPUT -- John Michael Britney OUTPUT-- male male female So this is the output I expect. I tried a lot to solve, but I really was not able to crack it. I will be really thankful to this site for giving me an opportunity to share this question. Actually this is asked in a programming contest as a flyer problem, so I thought this can be programmed.

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• Is it kEatSpeed or kSpeedEat?

  - by bobobobo

  I have a bunch of related constants that are not identical. What's the better way to name them? way #1 kWalkSpeed kRunSpeed kEatSpeed kDrinkSpeed Or, way #2 kSpeedWalk kSpeedRun kSpeedEat kSpeedDrink If we evaluate these based on readability understandability not bug prone with subtle errors due to using wrong variable name I think way #1 wins readability, they tie for understandability, and way #2 wins for not bug prone. I'm not sure how often it happens to others, but when variable names like this get long, then its easy to write kSpeedEatingWhenInAHurry when you really meant kSpeedEatingWhenInHome, especially when using autocomplete. Any perspectives?

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• Measuring how "heavily linked" a node is in a graph

  - by Eduardo León

  I have posted this question at MathOverflow.com as well. I am no mathematician and English is not my first language, so please excuse me if my question is too stupid, it is poorly phrased, or both. I am developing a program that creates timetables. My timetable-creating algorithm, besides creating the timetable, also creates a graph whose nodes represent each class I have already programmed, and whose arcs represent which pairs of classes should not be programmed at the same time, even if they have to be reprogrammed. The more "heavily linked" a node is, the more inflexible its associated class is with respect to being reprogrammed. Sometimes, in the middle of the process, there will be no option but to reprogram a class that has already been programmed. I want my program to be able to choose a class that, if reprogrammed, affects the least possible number of other already-programmed classes. That would mean choosing a node in the graph that is "not very heavily linked", subject to some constraints with respect to which nodes can be chosen. EDIT: The question was... Do you know any algorithm that measures how "heavily linked" a node is?

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• Find a regular expression that matches a string?

  - by Mirai

  I need a model for finding all of the regular expressions that would match a particular string. Basically, I need an algorithm for doing what I do to generate a regex search string from some pattern. My purpose for this to create a list of potential regular expressions from a selection of text and order that list from least specific (i.e. string of characters with abitrary length) to most specific (i.e. the string itself) to be used in text editor.

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• Starting a code library.

  - by Rob Stevenson-Leggett

  Hi, I've been meaning to start a library of reusable code snippets for a while and never seem to get round to it. I think my main problems are: Where to start. What structure should my library take? Should it be a compiled library (where appropriate or just classes I can drop into any project? Or a library project that can be included? In my experience, a built library will quickly become out of date and the source will get lost. So I'm leaning towards source libraries that I can export from SVN and include in any project. Intellectual property. I am employeed, so a lot of the code I write is not my IP. How can I ensure that I don't give my own IP away using it on projects in work and at home? I'm thinking the best way would be to licence my library with an open source licence and make sure I only add to it in my own time using my own equipment and therefore making sure that if I use it in a work project the same rules apply as if I was using a third party library. I write in many different languages and often would require two or more parts of this library. Should I look at implementing a few template projects and a core project for each of my chosen reusable components and languages? Has anyone else got this sort of library and how do you organise and update it?

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• Do similar passwords have similar hashes?

  - by SLC

  Our computer system at work requires users to change their password every few weeks, and you cannot have the same password as you had previously. It remembers something like 20 of your last passwords. I discovered most people simply increment a digit at the end of their password, so "thisismypassword1" becomes "thisismypassword2" then 3, 4, 5 etc. Since all of these passwords are stored somewhere, I wondered if there was any weakness in the hashes themselves, for standard hashing algorithms used to store passwords like MD5. Could a hacker increase their chances of brute-forcing the password if they have a list of hashes of similar passwords?

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• Tree-like queues

  - by Rehno Lindeque

  I'm implementing a interpreter-like project for which I need a strange little scheduling queue. Since I'd like to try and avoid wheel-reinvention I was hoping someone could give me references to a similar structure or existing work. I know I can simply instantiate multiple queues as I go along, I'm just looking for some perspective by other people who might have better ideas than me ;) I envision that it might work something like this: The structure is a tree with a single root. You get a kind of "insert_iterator" to the root and then push elements onto it (e.g. a and b in the example below). However, at any point you can also split the iterator into multiple iterators, effectively creating branches. The branches cannot merge into a single queue again, but you can start popping elements from the front of the queue (again, using a kind of "visitor_iterator") until empty branches can be discarded (at your discretion). x -> y -> z a -> b -> { g -> h -> i -> j } f -> b Any ideas? Seems like a relatively simple structure to implement myself using a pool of circular buffers but I'm following the "think first, code later" strategy :) Thanks

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• Determining the order of a list of numbers (possibly without sorting)

  - by Victor Liu

  I have an array of unique integers (e.g. val[i]), in arbitrary order, and I would like to populate another array (ord[i]) with the the sorted indexes of the integers. In other words, val[ord[i]] is in sorted order for increasing i. Right now, I just fill in ord with 0, ..., N, then sort it based on the value array, but I am wondering if we can be more efficient about it since ord is not populated to begin with. This is more of a question out of curiousity; I don't really care about the extra overhead from having to prepopulate a list and then sort it (it's small, I use insertion sort). This may be a silly question with an obvious answer, but I couldn't find anything online.

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• What do you enjoy about programming?

  - by Earlz

  Some of us here(or is it just me?) enjoy programming. Even if we're not being paid for it, and in some cases, even though the end result will not do anything for us. For example, many people do the Project Euler problems just for fun, and in the end nothing was really "accomplished" materially. What is it that makes us enjoy programming? How is programming different from another job? You don't see an accountant going home to do some accounting on their own time just for the pure joy of it. How are we different? (also, if anyone has some ideas on how to tag this, then please do correct it for me.. )

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• What is a typical algorithm for finding a string within a string?

  - by Courtney85

  I recently had an interview question that went something like this: Given a large string (haystack), find a substring (needle)? I was a little stumped to come up with a decent solution. What is the best way to approach this that doesn't have a poor time complexity?

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• Parsing: How to make error recovery in grammars like " a* b*"?

  - by Lavir the Whiolet

  Let we have a grammar like this: Program ::= a* b* where "*" is considered to be greedy. I usually implement "*" operator naively: Try to apply the expression under "*" to input one more time. If it has been applied successfully then we are still under current "*"-expression; try to apply the expression under "*" one more time. Otherwise we have reached next grammar expression; put characters parsed by expression under "*" back into input and proceed with next expression. But if there are errors in input in any of "a*" or "b*" part such a parser will "think" that in position of error both "a*" and "b*" have finished ("let's try "a"... Fail! OK, it looks like we have to proceed to "b*". Let's try "b"... Fail! OK, it looks like the string should have been finished...). For example, for string "daaaabbbbbbc" it will "say": "The string must end at position 1, delete superflous characters: daaaabbbbbbc". In short, greedy "*" operator becomes lazy if there are errors in input. How to make "*" operator to recover from errors nicely?

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• Please quickly help with this problem I got 52 minutes left.

  - by Hamish Grubijan

  Write a program that prints the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz". Woman said use any common language. Please make it short and test it. My screen is small. Thanks. P.S. I have test anxiety particularly after talking to people in suits. I also stayed up all night studying Java codes.

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• Consuming services that consume other services.

  - by phthomas

  What is the best way to confirm that these consumed services are actually up and running before I actually try to invoke its operation contracts? I want to do this so that I can gracefully display some message to the customer to give him/her a more pleasant user experience. Thanks.

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