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  • What is the cleanest way to use anonymous functions?

    - by Fletcher Moore
    I've started to use Javascript a lot more, and as a result I am writing things complex enough that organization is becoming a concern. However, this question applies to any language that allows you to nest functions. Essentially, when should you use an anonymous function over a named global or inner function? At first I thought it was the coolest feature ever, but I think I am going overboard. Here's an example I wrote recently, ommiting all the variable delcarations and conditionals so that you can see the structure. function printStream() { return fold(function (elem, acc) { ... var comments = (function () { return fold(function (comment, out) { ... return out + ...; }, '', elem.comments); return acc + ... + comments; }, '', data.stream); } I realized though (I think) there's some kind of beauty in being so compact, it is probably isn't a good idea to do this in the same way you wouldn't want a ton of code in a double for loop.

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  • How to prevent PHP variables from being arrays?

    - by MJB
    I think that (the title) is the problem I am having. I set up a MySQL connection, I read an XML file, and then I insert those values into a table by looping through the elements. The problem is, instead of inserting only 1 record, sometimes I insert 2 or 3 or 4. It seems to depend on the previous values I have read. I think I am reinitializing the variables, but I guess I am missing something -- hopefully something simple. Here is my code. I originally had about 20 columns, but I shortened the included version to make it easier to read. $ctr = 0; $sql = "insert into csd (id,type,nickname,hostname,username,password) ". "values (?,?,?,?,?,?)"; $cur = $db->prepare($sql); for ($ctr = 0; $ctr < $expected_count; $ctr++) { list ( $lbl, $type, $nickname, $hostname, $username, $password) = ""; $bind_vars = array(); $lbl = "csd_{$ctr}"; $type = $ref->itm->csds->$lbl->type; $nickname = $ref->itm->csds->$lbl->nickname; $hostname = $ref->itm->csds->$lbl->hostname; $username = $ref->itm->csds->$lbl->username; $password = $ref->itm->csds->$lbl->password; $bind_vars = array($id,$type,$nickname,$hostname,$username,$password); $res = $db->execute($cur, $bind_vars); # this is a separate function which works, but which only # does SELECTS and cannot be the problem. I include it because I # want to count the total rows. printf ("%d CSDs on that ITEM now.\n", CountCSDs($id_to_sync)); } P.S. I also tagged this SimpleXML because that is how I am reading the file, though that code is not included above. It looks like this: $Ref = simplexml_load_file($file);

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  • Multidimensional array (parent and childs)

    - by Juan
    I have a category system in a MySQL database with parents and childs. The database only stores the id of it''s immediate parent (or 0 if on root). Since the system allows multiple subcategories there are cases of multiple childs. For example [98] Storage [1] External [3] Pendrives [4] Portable hhdds [2] Internal [5] Sata hhdd [6] IDE hhdd [...] [99] Clothing The database would be id parent_id name 1 98 External 2 98 Internal 3 1 Pendrives 4 1 Portable 5 2 Sata 6 2 IDE 98 0 Storage 99 0 Clothing I also have a products table with a category id and I need to get a list of all the products in the first level of categories. For example: Product Category A 3 B 4 C 5 D 6 E 74 Should return 98: A, B, C, D 99: X, Y, Z... I'm stuck and I can't think of the logic to retrieve it in that way. I started by getting the IDs of all the categories that aren't in the first level by: while ($row = mysql_fetch_assoc($result)) { if ($row['parent_id'] != 0) { $level1[$i]['name'] = utf8_encode($row['categories_name']); $level1[$i]['id'] = $row['categories_id']; } $i++; } but I'm having a burnout and can't think of a way that would nest them. I thought some kind of while but it's infinite :P Any ideas please?

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  • Thread-safe data structure design

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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  • a question related to URL

    - by Robert
    Dear all,Now i have this question in my java program,I think it should be classified as URL problem,but not 100% sure.If you think I am wrong,feel free to recategorize this problem,thanks. I would state my problem as simply as possible. I did a search on the famouse Chinese search engine baidu.com for a Chinese key word "???" (Obama in English),and the way I do that is to pass a URL (in a Java Program)to the browser like: http://news.baidu.com/ns?word=??? and it works perfectly just like I input the "???”keyword in the text field on baidu.com. However,now my advisor wants another thing.Since he can not read the Chinese webpages,but he wants to make sure the webpages I got from Baidu.com is related to "Obama",he asked me to google translate it back,i.e,using google translate and translate the Chinese webpage to English one. This sounds straightforward.However,I met my problem here. If I simply pass the URL "http://news.baidu.com/ns?word=???" into Google Translate and tick "Chinese to English" translating option,the result looks awful.(I don't know the clue here,maybe related to Chinese character encoding). Alternatively,if now my browser opens ""http://news.baidu.com/ns?word=???" webpage,but I click on the "????" button (that simply means "search"),you will notice the URL will get changed,now if I pass this URL into the Google translate and do the same thing,the result works much better. I hope I am not making this problem sound too complicated,and I appologize for some Chinese words invovled,but I really need your guys' help here.Becasue I did all this in a Java program,I couldn't figure out how to realize that "????"(pressing search button) step then get the new URL.If I could get that new URL,things are easy,I could just call Google translate in my Java code,and pops out the new window to show my advisor. Please share any of your idea or thougts here.Thanks a lot. Robert

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  • Can I specify default value?

    - by atch
    Why is it that for user defined types when creating an array of objects every element of this array is initialized with default ctor but when I create built-in type this isn't the case? And second question: is it possible to specify default value to be used while initialize? Something like this (not valid): char* p = new char[size]('\0'); And another question in this topic while I'm with arrays. I suppose that when creating an array of user defined type and knowing the fact that every elem. of this array will be initialized with default value firstly why? If arrays for built in types do not initialize their elems. with their dflts why do they do it for UDT, and secondly: is there a way to switch it off/avoid/circumvent somehow? It seems like bit of a waste if I for example have created an array with size 10000 and then 10000 times dflt ctor will be invoked and I will (later on) overwrite this values anyway. I think that behaviour should be consistent, so either every type of array should be initialized or none. And I think that the behaviour for built-in arrays is more appropriate.

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  • Save result of for loop in a vector

    - by hendrik
    i think I'm just too tired to see the mistake. i wrote a function to get the maximal value for two data sets from a for loop plot_zu <- function(x) {for (i in 1:x){ z=data_raw[grep(a[i], data_raw$Gene.names),] b=data_raw_ace[grep(a[i], data_raw_ace$Gene.names),] p<-vector("numeric", length(1:length(a))) p[i]<-max(z$t_test_diff) return(p)} } so picture: a is a vector of names and the data set (data_raw(_ace)) are filtered by it. In the end i would like to have all maxima values of column t_test_diff in a vector. After that i want to add the t_test_diff column values from data_raw_ace also. So the problem is, that i get this: [1] 1.210213 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 [8] 0.000000 0.000000 So there is a problem with brackets or something but i cannot see it ( first value fits). Sorry for no good example but i think it is understandable and an easy to solve question. If im to dumb to explain my problem right, i will add an example. !! Thx a lot !! grateful Hendrik

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  • Web Shop Schema - Document Db

    - by Maxem
    I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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  • How to model a mutually exclusive relationship in sql server

    - by littlechris
    Hi, I have to add functionality to an existing application and I've run into a data situation that I'm not sure how to model. I am being restricted to the creation of new tables and code. If I need to alter the existing structure I think my client may reject the proposal..although if its the only way to get it right this is what I will have to do. I have an Item table that can me link to any number of tables, and these tables may increase over time. The Item can only me linked to one other table, but the record in the other table may have many items linked to it. Examples of the tables/entities being linked to are "Person", "Vehicle", "Building", "Office". These are all separate tables. Example of Items are "Pen", "Stapler", "Cushion", "Tyre", "A4 Paper", "Plastic Bag", "Poster", "Decoration" For instance a "Poster" may be allocated to a "Person" or "Office" or "Building". In the future if they add a "Conference Room" table it may also be added to that. My intital thoughts are: Item { ID, Name } LinkedItem { ItemID, LinkedToTableName, LinkedToID } The LinkedToTableName field will then allow me to identify the correct table to link to in my code. I'm not overly happy with this solution, but I can't quite think of anything else. Please help! :) Thanks!

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  • C++: is it safe to work with std::vectors as if they were arrays?

    - by peoro
    I need to have a fixed-size array of elements and to call on them functions that require to know about how they're placed in memory, in particular: functions like glVertexPointer, that needs to know where the vertices are, how distant they are one from the other and so on. In my case vertices would be members of the elements to store. to get the index of an element within this array, I'd prefer to avoid having an index field within my elements, but would rather play with pointers arithmetic (ie: index of Element *x will be x - & array[0]) -- btw, this sounds dirty to me: is it good practice or should I do something else? Is it safe to use std::vector for this? Something makes me think that an std::array would be more appropriate but: Constructor and destructor for my structure will be rarely called: I don't mind about such overhead. I'm going to set the std::vector capacity to size I need (the size that would use for an std::array, thus won't take any overhead due to sporadic reallocation. I don't mind a little space overhead for std::vector's internal structure. I could use the ability to resize the vector (or better: to have a size chosen during setup), and I think there's no way to do this with std::array, since its size is a template parameter (that's too bad: I could do that even with an old C-like array, just dynamically allocating it on the heap). If std::vector is fine for my purpose I'd like to know into details if it will have some runtime overhead with respect to std::array (or to a plain C array): I know that it'll call the default constructor for any element once I increase its size (but I guess this won't cost anything if my data has got an empty default constructor?), same for destructor. Anything else?

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  • Why does this MySQL function return null?

    - by Shore
    Description: the query actually run have 4 results returned,as can be see from below, what I did is just concate the items then return, but unexpectedly,it's null. I think the code is self-explanatory: DELIMITER | DROP FUNCTION IF EXISTS get_idiscussion_ask| CREATE FUNCTION get_idiscussion_ask(iask_id INT UNSIGNED) RETURNS TEXT DETERMINISTIC BEGIN DECLARE done INT DEFAULT 0; DECLARE body varchar(600); DECLARE created DATETIME; DECLARE anonymous TINYINT(1); DECLARE screen_name varchar(64); DECLARE result TEXT; DECLARE cur1 CURSOR FOR SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=iask_id; DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1; SET result = ''; OPEN cur1; REPEAT FETCH cur1 INTO body, created, anonymous, screen_name; SET result = CONCAT(result,'<comment><body><![CDATA[',body,']]></body>','<replier>',if(screen_name is not null and !anonymous,screen_name,''),'</replier>','<created>',created,'</created></comment>'); UNTIL done END REPEAT; CLOSE cur1; RETURN result; END | DELIMITER ; mysql> DELIMITER ; mysql> select get_idiscussion_ask(1); +------------------------+ | get_idiscussion_ask(1) | +------------------------+ | NULL | +------------------------+ 1 row in set (0.01 sec) mysql> SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=1; +------+---------------------+-----------+-------------+ | body | created | anonymous | screen_name | +------+---------------------+-----------+-------------+ | haha | 2009-05-27 04:57:51 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:53 | 0 | NULL | +------+---------------------+-----------+-------------+ 4 rows in set (0.00 sec) For those who don't think the code is self-explanatory: Why the function returns NULL?

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  • What effects has working in rotating shifts on programming teams?

    - by eKek0
    I work in a bank, and the boss now want's that we, the programming team, work on rotating shifts. He wants that sometimes we work from 7am to 3pm, and sometimes on 11.30am to 7.30pm. He says that we will be more productive working this way, because he has worked with teams just like that and he just knows that. Nobody of the team wants this change, but we don't know how to effectively reject this new rule. I was trying to find some empirical (or almost) evidence about how rotating shifts affects performance of programming teams, and I couldn't. I had read something about rotating shifts, but not exactly about the effect of this on programming teams. Do you know any research about rotating shifts on programming teams? Did you have any experience with this kind of work? EDIT: Other teams of the company, like the database administrators team, the help desk team, the communication team or the network administrators team are already working in rotating shifts, and they don't like this but they do it anyway. I think the boss want that we work on rotating shifts too because of them, but since only we do programming I think the effects of rotating shifts could be, at least, different for us.

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  • .NET Regular Expression to find actual words in text

    - by Mehdi Anis
    I am using VB .NET to write a program that will get the words from a suplied text file and count how many times each word appears. I am using this regular expression:- parser As New Regex("\w+") It gives me almost 100% correct words. Except when I have words like "Ms Word App file name is word.exe." or "is this a c# statment If(ab?1,0) ?" In such cases I get [word & exe] AND [If, a, b, 1 and 0] as seperate words. it would be nice (for my purpose) that I received word.exe and (If(ab?1,0) as words. I guess \w+ looks for white space, sentence terminating punctuation mark and other punctuation marks to determine a word. I want a similar regular Expression that will not break a word by a punctuation mark, if the punctuation mark is not the end of the word. I think end-of-word can be defined by a trailing WhiteSpace, Sentence terminating Punctuation (you may think of others). if you can suggest some regular expression 9for VB .NET) that will be great help. Thanks.

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  • Pass Linq Expression to a function

    - by Kushan Hasithe Fernando
    I want to pass a property list of a class to a function. with in the function based on property list I'm going to generate a query. As exactly same functionality in Linq Select method. Here I'm gonna implement this for Ingress Database. As an example, in front end I wanna run a select as this, My Entity Class is like this public class Customer { [System.Data.Linq.Mapping.ColumnAttribute(Name="Id",IsPrimaryKey=true)] public string Id { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Name")] public string Name { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Address")] public string Address { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Email")] public string Email { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Mobile")] public string Mobile { get; set; } } I wanna call a Select function like this, var result = dataAccessService.Select<Customer>(C=>C.Name,C.Address); then,using result I can get the Name and Address properties' values. I think my Select function should looks like this, ( *I think this should done using Linq Expression. But im not sure what are the input parameter and return type. * ) Class DataAccessService { // I'm not sure about this return type and input types, generic types. public TResult Select<TSource,TResult>(Expression<Func<TSource,TResult>> selector) { // Here using the property list, // I can get the ColumnAttribute name value and I can generate a select query. } } This is a attempt to create a functionality like in Linq. But im not an expert in Linq Expressions. There is a project call DbLinq from MIT, but its a big project and still i couldn't grab anything helpful from that. Can someone please help me to start this, or can someone link me some useful resources to read about this.

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • Generic InBetween Function.

    - by Luiscencio
    I am tired of writing x > min && x < max so i wawnt to write a simple function but I am not sure if I am doing it right... actually I am not cuz I get an error: bool inBetween<T>(T x, T min, T max) where T:IComparable { return (x > min && x < max); } errors: Operator '>' cannot be applied to operands of type 'T' and 'T' Operator '<' cannot be applied to operands of type 'T' and 'T' may I have a bad understanding of the where part in the function declaring note: for those who are going to tell me that I will be writing more code than before... think on readability =) any help will be appreciated EDIT deleted cuz it was resolved =) ANOTHER EDIT so after some headache I came out with this (ummm) thing following @Jay Idea of extreme readability: public static class test { public static comparision Between<T>(this T a,T b) where T : IComparable { var ttt = new comparision(); ttt.init(a); ttt.result = a.CompareTo(b) > 0; return ttt; } public static bool And<T>(this comparision state, T c) where T : IComparable { return state.a.CompareTo(c) < 0 && state.result; } public class comparision { public IComparable a; public bool result; public void init<T>(T ia) where T : IComparable { a = ia; } } } now you can compare anything with extreme readability =) what do you think.. I am no performance guru so any tweaks are welcome

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  • Scheduling Jobs On web server

    - by sirasad
    Hi Folks We Want to Create an online game like this.I think that ,this type of games have a scheduling software on web server. For Example : Player Click to create a resource And resource creation will be take a moment like 20 Minutes.(Every resource creation time will be different). This message will send to web server application but this message will not processed at same time for example must be processed after 20 Minutes. The web server application after getting the message must be put the order in the Queue. We have Some big problems : 1- The Jobs must be complete by the web server application Even the player Exit the Game. I think that we must create something like Windows service on Web Server. Can we do it? or Is there a better way? 2- The Second problem depended on problem 1 .Because we will have many Jobs (every player can create 20,30 Jobs in every Loggin and we will have thousands of users) , So Our Scheduling System Must be Work On time . it's possible that , there is 100 , 1000 jobs in a same second , if application Can't Done Jobs in him Second will be use the next second Time and the next second jobs will shift to next second and etc. How We can do for this problem ? Cheers Asad Safari Agile Coach , Scrum Master

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  • Neural Networks or Human-computer interaction

    - by Shahin
    I will be entering my third year of university in my next academic year, once I've finished my placement year as a web developer, and I would like to hear some opinions on the two modules in the Title. I'm interested in both, however I want to pick one that will be relevant to my career and that I can apply to systems I develop. I'm doing an Internet Computing degree, it covers web development, networking, database work and programming. Though I have had myself set on becoming a web developer I'm not so sure about that any more so am trying not to limit myself to that area of development. I know HCI would help me as a web developer, but do you think it's worth it? Do you think Neural Network knowledge could help me realistically in a system I write in the future? Thanks. EDIT: Hi guys, I thought it would be useful to follow-up with what I decided to do and how it's worked out. I picked Artificial Neural Networks over HCI, and I've really enjoyed it. Having a peek into cognitive science and machine learning has ignited my interest for the subject area, and I will be hoping to take on a postgraduate project a few years from now when I can afford it. I have got a job which I am starting after my final exams (which are in a few days) and I was indeed asked if I had done a module in HCI or similar. It didn't seem to matter, as it isn't a front-end developer position! I would recommend taking the module if you have it as an option, as well as any module consisting of biological computation, it will open up more doors should you want to go onto postgraduate research in the future. Thanks again, Shahin

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  • Avoiding a fork()/SIGCHLD race condition

    - by larry
    Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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  • Is there a fundamental difference between malloc and HeapAlloc (aside from the portability)?

    - by Lambert
    Hi, I'm having code that, for various reasons, I'm trying to port from the C runtime to one that uses the Windows Heap API. I've encountered a problem: If I redirect the malloc/calloc/realloc/free calls to HeapAlloc/HeapReAlloc/HeapFree (with GetProcessHeap for the handle), the memory seems to be allocated correctly (no bad pointer returned, and no exceptions thrown), but the library I'm porting says "failed to allocate memory" for some reason. I've tried this both with the Microsoft CRT (which uses the Heap API underneath) and with another company's run-time library (which uses the Global Memory API underneath); the malloc for both of those works well with the library, but for some reason, using the Heap API directly doesn't work. I've checked that the allocations aren't too big (= 0x7FFF8 bytes), and they're not. The only problem I can think of is memory alignment; is that the case? Or other than that, is there a fundamental difference between the Heap API and the CRT memory API that I'm not aware of? If so, what is it? And if not, then why does the static Microsoft CRT (included with Visual Studio) take some extra steps in malloc/calloc before calling HeapAlloc? I'm suspecting there's a difference but I can't think of what it might be. Thank you!

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  • How can I change the VisualState in a View from the ViewModel?

    - by Decker
    I'm new to WPF and MVVM. I think this is a simple question. My ViewModel is performing an asynch call to obtain data for a DataGrid which is bound to an ObservableCollection in the ViewModel. When the data is loaded, I set the proper ViewModel property and the DataGrid displays the data with no problem. However, I want to introduce a visual cue for the user that the data is loading. So, using Blend, I added this to my markup: <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="LoadingStateGroup"> <VisualState x:Name="HistoryLoading"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="HistoryGrid"> <DiscreteObjectKeyFrame KeyTime="0" Value="{x:Static Visibility.Hidden}"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="HistoryLoaded"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="WorkingStackPanel"> <DiscreteObjectKeyFrame KeyTime="0" Value="{x:Static Visibility.Hidden}"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> </VisualStateGroup> </VisualStateManager.VisualStateGroups> I think I know how to change the state in my code-behind (something similar to this): VisualStateManager.GoToElementState(LayoutRoot, "HistoryLoaded", true); However, the place where I want to do this is in the I/O completion method of my ViewModel which does not have a reference to it's corresponding View. How would I accomplish this using the MVVM pattern?

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  • Beginner Question: For extract a large subset of a table from MySQL, how does Indexing, order of tab

    - by chongman
    Sorry if this is too simple, but thanks in advance for helping. This is for MySQL but might be relevant for other RDMBSs tblA has 4 columns: colA, colB, colC, mydata, A_id It has about 10^9 records, with 10^3 distinct values for colA, colB, colC. tblB has 3 columns: colA, colB, B_id It has about 10^4 records. I want all the records from tblA (except the A_id) that have a match in tblB. In other words, I want to use tblB to describe the subset that I want to extract and then extract those records from tblA. Namely: SELECT a.colA, a.colB, a.colC, a.mydata FROM tblA as a INNER JOIN tblB as b ON a.colA=b.colA a.colB=b.colB ; It's taking a really long time (more than an hour) on a newish computer (4GB, Core2Quad, ubuntu), and I just want to check my understanding of the following optimization steps. ** Suppose this is the only query I will ever run on these tables. So ignore the need to run other queries. Now my questions: 1) What indexes should I create to optimize this query? I think I just need a multiple index on (colA, colB) for both tables. I don't think I need separate indexes for colA and colB. Another stack overflow article (that I can't find) mentioned that when adding new indexes, it is slower when there are existing indexes, so that might be a reason to use the multiple index. 2) Is INNER JOIN correct? I just want results where a match is found. 3) Is it faster if I join (tblA to tblB) or the other way around, (tblB to tblA)? This previous answer says that the optimizer should take care of that. 4) Does the order of the part after ON matter? This previous answer say that the optimizer also takes care of the execution order.

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  • How to know why an animation stutters?

    - by Patrick Klug
    I have a few fairly simple animations (moving text around, moving ellipses etc.) and running in full screen (1920x1080 minus the task bar) the WPF Performance Suite reports a good framerate around 50 FPS throughout the animation. Dirty Rect Addition is somewhere around 300 rect/s, the SW frames are between 0 and 4 and the HW frames are between 3 and 5. Video memory usage is around 80 MB. Problem is that the animations stutters every other half second. My machine is a new Dell laptop XPS 15 with the GeForce GT 435 with 2GB memory. - The drivers are up to date. (The same behavior occurs on my netbook (in full screen) as well so I don't think it is hardware related.) If I make the window smaller the stutter goes away. The stutter occurs with the simplest of animations - even with just a couple of elements but adding more elements certainly makes it more noticeable. How can I find out what causes this stutter? When I think of it, I have not actually seen any WPF animations which run smoothly in full screen. Is this even possible?

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  • how could application installations/configurations be easier in linux? [closed]

    - by ajsie
    although you can do anything in linux it tends to require a lot of tweaking in config files and reading a lot of manuals/tutorials before you can have it running in your way. i know that it gets a lot easier by time, and the apt-get installations with ubuntu/debian is heading the right way. but how can linux be more userfriendly for us in the future? i thought that if more is automated like an IDE environment, eg. typing svn will give us all the commands and description about each command when you move between commands with your keyboard. that would be great. but that's just one example. another is the navigation in the terminal between folders. now you have to type a lot just to jump from/to different folders. would be great with some more automatization here too. i know that these extra features will slow down the server, but its 2010 now, and these features are not that heavy for the cpu, but makes it more userfriendly and encourage maintainance of a server, not frighten u off. what do you think about this? should/could we have more user friendly linux environment in servers, something that has annoyed you a lot? a lot of things are done in the unix way, but maybe we should reinvent the wheel in some areas, cause apparently, its so...repeatingly today and difficult to do easy tasks. it should be easier i think..

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  • Alignment in assembly

    - by jena
    Hi, I'm spending some time on assembly programming (Gas, in particular) and recently I learned about the align directive. I think I've understood the very basics, but I would like to gain a deeper understanding of its nature and when to use alignment. For instance, I wondered about the assembly code of a simple C++ switch statement. I know that under certain circumstances switch statements are based on jump tables, as in the following few lines of code: .section .rodata .align 4 .align 4 .L8: .long .L2 .long .L3 .long .L4 .long .L5 ... .align 4 aligns the following data on the next 4-byte boundary which ensures that fetching these memory locations is efficient, right? I think this is done because there might be things happening before the switch statement which caused misalignment. But why are there actually two calls to .align? Are there any rules of thumb when to call .align or should it simply be done whenever a new block of data is stored in memory and something prior to this could have caused misalignment? In case of arrays, it seems that alignment is done on 32-byte boundaries as soon as the array occupies at least 32 byte. Is it more efficient to do it this way or is there another reason for the 32-byte boundary? I'd appreciate any explanation or hint on literature.

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