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• Culture Sensitive GetHashCode

  - by user114928

  Hi, I'm writing a c# application that will process some text and provide basic query functions. In order to ensure the best possible support for other languages, I am allowing the users of the application to specify the System.Globalization.CultureInfo (via the "en-GB" style code) and also the full range of collation options using the System.Globalization.CompareOptions flags enum. For regular string comparison I'm then using a combination of: a) String.Compare overload that accepts the culture and options b) For some bulk processes I'm caching the byte data (KeyData) from CompareInfo.GetSortKey (overload that accepts the options) and using a byte-by-byte comparison of the KeyData. This seemed fine (although please comment if you think these two methods shouldn't be mixed), but then I had reason to use the HashSet< class which only has an overload for IEqualityComparer<. MS documentation seems to suggest that I should use StringComparer (which implements both IEqualityComparer< and IComparer<), but this only seems to support the "IgnoreCase" option from CompareOptions and not "IgnoreKanaType", "IgnoreSymbols", "IgnoreWidth" etc. I'm assuming that a StringComparer that ignores these other options could produce different hashcodes for two strings that might be considered the same using my other comparison options. I'd therefore get incorrect results from my application. Only thought at the moment is to create my own IEqualityComparer< that generates a hashcode from the SortKey.KeyData and compares eqality be using the String.Compare overload. Any suggestions?

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• TortoiseSVN lists files as modified, but they are identical

  - by BJ Safdie

  I am merging a hot fix from our QA branch back into our Dev branch. Five files have changed. I do a fresh checkout of the Dev branch. I then do a merge (range of revisions) from QA into the Dev working copy. It brings in five files and there is a conflict on an external and ignore property -- which I resolve by "using local" (dev). When I check modifications or commit, I expect to see the five files I merged as the only changes. However, I get close to 700 "modified" files showing up in the commit dialog. If I select one of these file and "Compare with base," WinMerge comes up and says the "files are identical." I have tried this with the file dates set to "last committed" and not. Why are all of these files showing up as modified, when they are identical? What in the merge is causing this? How do I prevent SVN/TortoiseSVN from getting confused this way in the future?

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• Jquery animate bottom problem

  - by andrea

  It's strange. I have an animation that start when i .hover on a DIV. Into this div i have another in position absolute that i want to move up until the mouse stay on main div and go down in your position when i go out of main div. A simple hover effect. I have write down this function that work well apart a strange bug. var inside = $('.inside') inside.hover(function() { $(this).children(".coll_base").stop().animate({ bottom:'+=30px' },"slow") }, function() { $(this).children(".coll_base").stop().animate({ bottom:'-=30px' },"slow"); }); i need +=30 and -=30 because i have to apply this function to a range of div with different bottom. The problem is that if i hover on and out of div the DIV animate right but when go down he decrease the value of bottom every animation. If i go up and down from the main div i see that the animated div go down even beyond the main div. I think that i miss something to resolve this bug. Thanks for any help

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• Binary Search Tree for specific intent

  - by Luís Guilherme

  We all know there are plenty of self-balancing binary search trees (BST), being the most famous the Red-Black and the AVL. It might be useful to take a look at AA-trees and scapegoat trees too. I want to do deletions insertions and searches, like any other BST. However, it will be common to delete all values in a given range, or deleting whole subtrees. So: I want to insert, search, remove values in O(log n) (balanced tree). I would like to delete a subtree, keeping the whole tree balanced, in O(log n) (worst-case or amortized) It might be useful to delete several values in a row, before balancing the tree I will most often insert 2 values at once, however this is not a rule (just a tip in case there is a tree data structure that takes this into account) Is there a variant of AVL or RB that helps me on this? Scapegoat-trees look more like this, but would also need some changes, anyone who has got experience on them can share some thougts? More precisely, which balancing procedure and/or removal procedure would help me keep this actions time-efficient?

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• How to Implement Overlay blend method using opengles 1.1

  - by Cylon

  Blow is the algorithm of overlay. and i want using it on iphone, but iphone 3g only support opengles 1.1, can not using glsl. can i using blend function or texture combine to implement it. thank you /////////Reference from OpenGL Shading® Language Third Edition /////////// 19.6.12 Overlay OVERLAY first computes the luminance of the base value. If the luminance value is less than 0.5, the blend and base values are multiplied together. If the luminance value is greater than 0.5, a screen operation is performed. The effect is that the base value is mixed with the blend value, rather than being replaced. This allows patterns and colors to overlay the base image, but shadows and highlights in the base image are preserved. A discontinuity occurs where luminance = 0.5. To provide a smooth transition, we actually do a linear blend of the two equations for luminance in the range [0.45,0.55]. float luminance = dot(base, lumCoeff); if (luminance < 0.45) result = 2.0 * blend * base; else if (luminance 0.55) result = white - 2.0 * (white - blend) * (white - base); else { vec4 result1 = 2.0 * blend * base; vec4 result2 = white - 2.0 * (white - blend) * (white - base); result = mix(result1, result2, (luminance - 0.45) * 10.0); }

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• How to perform Rails model validation checks within model but outside of filters using ledermann-rails-settings and extensions

  - by user1277160

  Background I'm using ledermann-rails-settings (https://github.com/ledermann/rails-settings) on a Rails 2/3 project to extend virtually the model with certain attributes that don't necessarily need to be placed into the DB in a wide table and it's working out swimmingly for our needs. An additional reason I chose this Gem is because of the post How to create a form for the rails-settings plugin which ties ledermann-rails-settings more closely to the model for the purpose of clean form_for usage for administrator GUI support. It's a perfect solution for addressing form_for support although... Something that I'm running into now though is properly validating the dynamic getters/setters before being passed to the ledermann-rails-settings module. At the moment they are saved immediately, regardless if the model validation has actually fired - I can see through script/console that validation errors are being raised. Example For instance I would like to validate that the attribute :foo is within the range of 0..100 for decimal usage (or even a regex). I've found that with the previous post that I can use standard Rails validators (surprise, surprise) but I want to halt on actually saving any values until those are addressed - ensure that the user of the GUI has given 61.43 as a numerical value. The following code has been borrowed from the quoted post. class User < ActiveRecord::Base has_settings validates_inclusion_of :foo, :in => 0..100 def self.settings_attr_accessor(*args) >>SOME SORT OF UNLESS MODEL.VALID? CHECK HERE args.each do |method_name| eval " def #{method_name} self.settings.send(:#{method_name}) end def #{method_name}=(value) self.settings.send(:#{method_name}=, value) end " end >>END UNLESS end settings_attr_accessor :foo end Anyone have any thoughts here on pulling the state of the model at this point outside of having to put this into a before filter? The goal here is to be able to use the standard validations and avoid rolling custom validation checks for each new settings_attr_accessor that is added. Thanks!

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• Why does adding Crossover to my Genetic Algorithm give me worse results?

  - by MahlerFive

  I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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• problem with evolutionary algorithms degrading into simulated annealing: mutation too small?

  - by Schnalle

  i have a problem understanding evolutionary algorithms. i tried using this technique several times, but i always ran into the same problem: degeneration into simulated annealing. lets say my initial population, with fitness in brackets, is: A (7), B (9), C (14), D (19) after mating and mutation i have following children: AB (8.3), AC (12.2), AD (14.1), BC(11), BD (14.7), CD (17) after elimination of the weakest, we get A, AB, B, AC next turn, AB will mate again with a result around 8, pushing AC out. next turn, AB again, pushing B out (assuming mutation changes fitness mostly in the 1 range). now, after only a few turns the pool is populated with the originally fittest candidates (A, B) and mutations of those two (AB). this happens regardless of the size of the initial pool, it just takes a bit longer. say, with an initial population of 50 it takes 50 turns, then all others are eliminated, turning the whole setup in a more complicated simulated annealing. in the beginning i also mated canditates with themselves, worsening the problem. so, what do i miss? are my mutation rates simply too small and will it go away if i increase them? here's the project i'm using it for: http://stefan.schallerl.com/simuan-grid-grad/ yeah, the code is buggy and the interface sucks, but i'm too lazy to fix it right now - and be careful, it may lock up your browser. better use chrome, even thought firefox is not slower than chrome for once (probably the tracing for the image comparison pays off, yay!). if anyone is interested, the code can be found here. here i just dropped the ev-alg idea and went for simulated annealing. ps: i'm not even sure about simulated annealing - it is like evolutionary algorithms, just with a population size of one, right?

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• Ranking/ weighing search result

  - by biso

  I am trying to build an application that has a smart adaptive search engine (lets say for cars). If I search for for 4x4 then the DB will return all the 4x4 cars I have (100 cars) - but as time goes by and I start checking out cars, liking them, commenting on them, etc the order of the search result should be the different. That means 1 month later when searching for 4x4, I should get the same result set ordered differently as per my previous interaction with the site. If I was mainly liking and commenting on German cars, BMW should be on the top and Land cruiser should be further down. This ranking should be based on attributes that I captureduring user interaction (eg: car origin, user age, user location, car type[4x4, coupe, hatchback], price range). So for each car result I get, I will be weighing it based on how well it is performing on the 5 attributes above. I intend to use the DB just as a repository and do the ranking and the thinking on the server. My question is, what kind of algorithm should I be using to weigh/rank my search result? Thanks.

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• retrieving multiple versions through API through hbase

  - by sammy

  hello , this is a continuation of my previous question where id used hbase shell.. http://stackoverflow.com/questions/3024417/facing-problems-while-updating-rows-in-hbase i tried the same with API.. im not able to figure out how to retrieve all versions , iterate and print their values for a specific row... i've spending hours reading... please help me out... Scan s = new Scan(Bytes.toBytes("row1")); s.addColumn(Bytes.toBytes("column"),Bytes.toBytes("address")); SETTING RANGE FOR THE VERSIONS s.setTimeRange(0L,6L); ResultScanner scanner = table.getScanner(s); for (Result r : scanner) { for(KeyValue kv : r.sorted()) { System.out.println("To"+kv.getTimestamp()); System.out.println("from "+Bytes.toString(kv.getKey())); System.out.println("To "+Bytes.toString(kv.getValue())); } scanner.close(); } here im intending to print all versions of the column..... but it gives the most recent one... im stuck here...

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• boost::spirit (qi) decision between float and double

  - by ChrisInked

  I have a parser which parses different data types from an input file. I already figured out, that spirit can decide between short and int, for example: value %= (shortIntNode | longIntNode); with shortIntNode %= (qi::short_ >> !qi::double_) [qi::_val = phoenix::bind(&CreateShortIntNode, qi::_1)]; longIntNode %= (qi::int_ >> !qi::double_) [qi::_val = phoenix::bind(&CreateLongIntNode, qi::_1)]; I used this type of rules to detect doubles as well (from the answers here and here). The parser was able to decide between int for numbers 65535 and short for numbers <= 65535. But, for float_ and double_ it does not work as expected. It just rounds these values to parse it into a float value, if there is a rule like this: value %= (floatNode | doubleFloatNode); with floatNode %= (qi::float_) [qi::_val = phoenix::bind(&CreateFloatNode, qi::_1)]; doubleFloatNode %= (qi::double_) [qi::_val = phoenix::bind(&CreateDoubleFloatNode, qi::_1)]; Do you know if there is something like an option or some other trick to decide between float_ and double_ depending on the data type range? Thank you very much!

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• Returning large collections from WCF Serivce

  - by Nate Bross

  I'm trying to determine the best approach for building a WCF Service, and the area I'm struggling with most is returning lists of objects. The built-in maxMessageSize of 64k seems pretty high, and I really don't want to bump it up (quick googling finds 100s of places bumping the maxMessageSize up to multi-gigabyte range which seems foolish). But, when I'm returning a collection of objects (~150 items) I am exceeding the default 64k. I'm almost to the point of returning my own class which inherits IEnumerable and has properties for hasNext, hasPrevious and PageSize so that I can implement paging on the client side -- this seems like alot of code. The other option is to jackup the maxMessageSize and hope for the best, but that feels wrong. All other aspects of my service are working great, its just returning large collectiosn where I'm having issues. For background, there are two types of consumers of this service, UI applications which will be primarly web and/or wpf applications, and data processing applications, .NET console apps, and maybe some other non-UI apps. For the UI applications, I would like to keep them responsive and keep the messageSize low, on the console apps it doesn't matter as much as they are just pulling data down to do processing and push it back up to the service.

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• Trying to calculate large numbers in Python with gmpy. Python keeps crashing?

  - by Ryan Peschel

  I was recommended to use gmpy to assist with calculating large numbers efficiently. Before I was just using python and my script ran for a day or two and then ran out of memory (not sure how that happened because my program's memory usage should basically be constant throughout.. maybe a memory leak?) Anyways, I keep getting this weird error after running my program for a couple seconds: mp_allocate< 545275904->545275904 > Fatal Python error: mp_allocate failure This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. Also, python crashes and Windows 7 gives me the generic python.exe has stopped working dialog. This wasn't happening with using standard python integers. Now that I switch to gmpy I am getting this error just seconds in to running my script. I thought gmpy was specialized in dealing with large number arithmetic? For reference, here is a sample program that produces the error: import gmpy2 p = gmpy2.xmpz(3000000000) s = gmpy2.xmpz(2) M = s**p for x in range(p): s = (s * s) % M I have 10 gigs of RAM and without gmpy this script ran for days without running out of memory (still not sure how that happened considering s never really gets larger.. Anyone have any ideas? EDIT: Forgot to mention I am using Python 3.2

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• php fopen function dies, though I have file permissions set to read and write

  - by Matthew Robert Keable

  I'm following a tutorial on php, and am having difficulty getting this to work. I set the appropriate directory permissions to read and write, but every time I run this, I get the die string. The code is: $ourFileName = "testFile.txt"; $ourFileHandle = fopen($ourFileName, 'w') or die("can't open file"); fclose($ourFileHandle); As far as my basic understanding goes, if "testFile.txt" does not exist, fopen should create that file (I have basic knowledge of Python, and remember this same principle in that language). But it...it doesn't. Even if I create the aforementioned file, and put it up, that line of code still returns a die string. My hosting account does not give me permission to execute. Is this a problem? My server runs on Windows. I am using Dreamweaver CS5, on OSX 10.5.8. I've done some searching on this, and see other people having similar issues - but none of them keyed to exactly my range of problems. Being that I'm a beginner, I feel that it might be something I'm overlooking. Thanks!!

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• How to make std::vector's operator[] compile doing bounds checking in DEBUG but not in RELEASE

  - by Edison Gustavo Muenz

  I'm using Visual Studio 2008. I'm aware that std::vector has bounds checking with the at() function and has undefined behaviour if you try to access something using the operator [] incorrectly (out of range). I'm curious if it's possible to compile my program with the bounds checking. This way the operator[] would use the at() function and throw a std::out_of_range whenever something is out of bounds. The release mode would be compiled without bounds checking for operator[], so the performance doesn't degrade. I came into thinking about this because I'm migrating an app that was written using Borland C++ to Visual Studio and in a small part of the code I have this (with i=0, j=1): v[i][j]; //v is a std::vector<std::vector<int> > The size of the vector 'v' is [0][1] (so element 0 of the vector has only one element). This is undefined behaviour, I know, but Borland is returning 0 here, VS is crashing. I like the crash better than returning 0, so if I can get more 'crashes' by the std::out_of_range exception being thrown, the migration would be completed faster (so it would expose more bugs that Borland was hiding).

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• Mysql select - improve performance

  - by realshadow

  Hey, I am working on an e-shop which sells products only via loans. I display 10 products per page in any category, each product has 3 different price tags - 3 different loan types. Everything went pretty well during testing time, query execution time was perfect, but today when transfered the changes to the production server, the site "collapsed" in about 2 minutes. The query that is used to select loan types sometimes hangs for ~10 seconds and it happens frequently and thus it cant keep up and its hella slow. The table that is used to store the data has approximately 2 milion records and each select looks like this: SELECT * FROM products_loans WHERE KOD IN("X17/Q30-10", "X17/12", "X17/5-24") AND 369.27 BETWEEN CENA_OD AND CENA_DO; 3 loan types and the price that needs to be in range between CENA_OD and CENA_DO, thus 3 rows are returned. But since I need to display 10 products per page, I need to run it trough a modified select using OR, since I didnt find any other solution to this. I have asked about it here, but got no answer. As mentioned in the referencing post, this has to be done separately since there is no column that could be used in a join (except of course price and code, but that ended very, very badly). Here is the show create table, kod and CENA_OD/CENA_DO very indexed via INDEX. CREATE TABLE `products_loans` ( `KOEF_ID` bigint(20) NOT NULL, `KOD` varchar(30) NOT NULL, `AKONTACIA` int(11) NOT NULL, `POCET_SPLATOK` int(11) NOT NULL, `koeficient` decimal(10,2) NOT NULL default '0.00', `CENA_OD` decimal(10,2) default NULL, `CENA_DO` decimal(10,2) default NULL, `PREDAJNA_CENA` decimal(10,2) default NULL, `AKONTACIA_SUMA` decimal(10,2) default NULL, `TYP_VYHODY` varchar(4) default NULL, `stage` smallint(6) NOT NULL default '1', PRIMARY KEY (`KOEF_ID`), KEY `CENA_OD` (`CENA_OD`), KEY `CENA_DO` (`CENA_DO`), KEY `KOD` (`KOD`), KEY `stage` (`stage`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 And also selecting all loan types and later filtering them trough php doesnt work good, since each type has over 50k records and the select takes too much time as well... Any ides about improving the speed are appreciated.

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• Get the equivalent time between "dynamic" time zones

  - by doctore

  I have a table providers that has three columns (containing more columns but not important in this case): starttime, start time in which you can contact him. endtime, final hour in which you can contact him. region_id, region where the provider resides. In USA: California, Texas, etc. In UK: England, Scotland, etc starttime and endtime are time without timezone columns, but, "indirectly", their value has time zone of the region in which the provider resides. For example: starttime | endtime | region_id (time zone of region) | "real" st | "real" et ----------|----------|---------------------------------|-----------|----------- 03:00:00 | 17:00:00 | 1 (EGT => -1) | 02:00:00 | 16:00:00 Often I need to get the list of suppliers whose time range is within the current server time (taking into account the time zone conversion). The problem is that the time zones aren't "constant", ie, they may change during the summer time. However, this change is very specific to the region and not always carried out at the same time: EGT <= EGST, ART <= ARST, etc. The question is: 1. Is it necessary to use a webservice to update every so often the time zones in the regions? Does anyone know of a web service that can serve? 2. Is there a better approach to solve this problem? Thanks in advance. UPDATE I will give an example to clarify what I'm trying to get. In the table providers I found this records: idproviders | starttime | endtime | region_id ------------|-----------|----------|----------- 1 | 03:00:00 | 17:00:00 | 23 (Texas) 2 | 04:00:00 | 18:00:00 | 23 (Texas) If I execute the query in January, with this information: Server time (UTC offset) = 0 hours Texas providers (UTC offset) = +1 hour Server time = 02:00:00 I should get the following results: idproviders = 1 If I execute the query in June, with this information: Server time (UTC offset) = 0 hours Texas providers (UTC offset) = +2 hours (their local time has not changed, but their time zone has changed) Server time = 02:00:00 I should get the following results: idproviders = 1 and 2

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• Losing URI segments when paginating with CodeIgniter

  - by Danny Herran

  I have a /payments interface where the user should be able to filter via price range, bank, and other stuff. Those filters are standard select boxes. When I submit the filter form, all the post data goes to another method called payments/search. That method performs the validation, saves the post values into a session flashdata and redirects the user back to /payments passing the flashdata name via URL. So my standard pagination links with no filters are exactly like this: payments/index/20/ payments/index/40/ payments/index/60/ And if you submit the filter form, the returning URL is: payments/index/0/b48c7cbd5489129a337b0a24f830fd93 This works just great. If I change the zero for something else, it paginates just fine. The only issue however is that the << 1 2 3 4 page links wont keep the hash after the pagination offset. CodeIgniter is generating the page links ignoring that additional uri segment. My uri_segment config is already set to 3: $config['uri_segment'] = 3; I cannot set the page offset to 4 because that hash may or may not exists. Any ideas of how can I solve this? Is it mandatory for CI to have the offset as the last segment in the uri? Maybe I am trying an incorrect approach, so I am all ears. Thank you folks.

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• Accept templated parameter of stl_container_type<string>::iterator

  - by Rodion Ingles

  I have a function where I have a container which holds strings (eg vector<string>, set<string>, list<string>) and, given a start iterator and an end iterator, go through the iterator range processing the strings. Currently the function is declared like this: template< typename ContainerIter> void ProcessStrings(ContainerIter begin, ContainerIter end); Now this will accept any type which conforms to the implicit interface of implementing operator*, prefix operator++ and whatever other calls are in the function body. What I really want to do is have a definition like the one below which explicitly restricts the amount of input (pseudocode warning): template< typename Container<string>::iterator> void ProcessStrings(Container<string>::iterator begin, Container<string>::iterator end); so that I can use it as such: vector<string> str_vec; list<string> str_list; set<SomeOtherClass> so_set; ProcessStrings(str_vec.begin(), str_vec.end()); // OK ProcessStrings(str_list.begin(), str_list.end()); //OK ProcessStrings(so_set.begin(), so_set.end()); // Error Essentially, what I am trying to do is restrict the function specification to make it obvious to a user of the function what it accepts and if the code fails to compile they get a message that they are using the wrong parameter types rather than something in the function body that XXX function could not be found for XXX class.

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• Plotting an Arc in Discrete Steps

  - by phobos51594

  Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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• Go - Using a map for its set properties with user defined types

  - by Seth Hoenig

  I'm trying to use the built-in map type as a set for a type of my own (Point, in this case). The problem is, when I assign a Point to the map, and then later create a new, but equal point and use it as a key, the map behaves as though that key is not in the map. Is this not possible to do? // maptest.go package main import "fmt" func main() { set := make(map[*Point]bool) printSet(set) set[NewPoint(0, 0)] = true printSet(set) set[NewPoint(0, 2)] = true printSet(set) _, ok := set[NewPoint(3, 3)] // not in map if !ok { fmt.Print("correct error code for non existent element\n") } else { fmt.Print("incorrect error code for non existent element\n") } c, ok := set[NewPoint(0, 2)] // another one just like it already in map if ok { fmt.Print("correct error code for existent element\n") // should get this } else { fmt.Print("incorrect error code for existent element\n") // get this } fmt.Printf("c: %t\n", c) } func printSet(stuff map[*Point]bool) { fmt.Print("Set:\n") for k, v := range stuff { fmt.Printf("%s: %t\n", k, v) } } type Point struct { row int col int } func NewPoint(r, c int) *Point { return &Point{r, c} } func (p *Point) String() string { return fmt.Sprintf("{%d, %d}", p.row, p.col) } func (p *Point) Eq(o *Point) bool { return p.row == o.row && p.col == o.col }

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• Segmentation in Linux : Segmentation & Paging are redundant?

  - by claws

  Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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• A standard set of questions to ask an interviewer?

  - by Rob Wells

  We have had many questions for interviewers to ask interviewees. But none addressing information flow in the other direction, interviewee to interviewer. Just an indirect question about "deal breakers" and one about "finding dream jobs". What I'm after is when you're interviewing at a company do you have a set of questions that you like to ask to help get a feel for the company and the work environment? I have a series of questions that I like to ask that range from the development environment to testing techniques to how the team get on together. Anything else you'd like to ask? Edit: I moved my original list of interviewer questions to my answer below. I've also gone through the other answers and added the ones thought were useful in to that answer. The answer is community wiki so feel free to add anything useful. N.B. This is my first cut of categories. Feel free to modify/add/etc. the categories. Or to recategorise the questions themselves.

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• Get a selected radio button value after POST to set other fields enabled/disabled

  - by Redeemed1

  I have an MVC application with a simple control to all selection of All Dates or selecting a Date Range. The radio buttons have an onclick handler to enable/disable the dat pickers. All work well so far. When I try to set the correct context state for the datepickers after doing a POST I cannot get the jQuery selector to return the radio buttons checked value. The code is as follows: <%= Html.RadioButton("DateSelection.AllDates", "AllDates", Model.AllDates == "AllDates", new { onclick = "setReadOnly(this);" })%>ALL Dates&nbsp; <%= Html.RadioButton("DateSelection.AllDates", "Selection", Model.AllDates == "Selection", new { onclick = "setReadOnly(this);" })%>Selection <%= Html.DatePicker("DateSelection.startdate", Model.StartDate, "", "") %> &nbsp;To&nbsp;<%= Html.DatePicker("DateSelection.enddate", Model.EndDate, "", "") %><br /> The javascript is as follows: <script type="text/jscript" > function setReadOnly(obj) { if (obj.value == "Selection") { $('#DateSelection_startdate').css('backgroundColor', '#ffffff') .removeAttr('readonly') .datepicker('enable'); $('#DateSelection_enddate').css('backgroundColor', '#ffffff') .removeAttr('readonly') .datepicker('enable'); } else { $('#DateSelection_startdate').css('backgroundColor', '#eeeeee') .attr('readonly', 'readonly') .val('') .datepicker('disable'); $('#DateSelection_enddate').css('backgroundColor', '#eeeeee') .attr('readonly', 'readonly') .val('') .datepicker('disable'); } } <script type="text/jscript"> $(document).ready(function() { $('#DateSelection_startdate').datepicker('disable').css('backgroundColor', '#eeeeee') .attr('readonly', 'readonly') .val(''); $('#DateSelection_enddate').datepicker('disable').css('backgroundColor', '#eeeeee') .attr('readonly', 'readonly') .val(''); var selected = $('#DateSelection_AllDates:checked'); setReadOnly(selected); }); The javascript line that is causing the problem is var selected = $('#DateSelection_AllDates:checked'); which will NOT return the checked radio button. Using var selected = $('#DateSelection_AllDates'); will return the first radio button value as expected i.e. applying the ':checked' filter ALWAYS returns undefined. Can anyone see anything wrong here?

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