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  • default model field attribute in Django

    - by Rosarch
    I have a Django model: @staticmethod def getdefault(): print "getdefault called" return cPickle.dumps(set()) _applies_to = models.TextField(db_index=True, default=getdefault) For some reason, getdefault() is never called, even as I construct instances of this model and save them to the database. This seems to contradict the Django documentation: Field.default The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created. Am I doing something wrong? Update: Originally, I had this, but then I switched to the above version to debug: _applies_to = models.TextField(db_index=True, default=cPickle.dumps(set())) I'm not sure why that wouldn't work.

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  • Want to understand C++ sentry object

    - by Romain Hippeau
    I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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  • XPath conditional text node selection

    - by Reinderien
    Hi there. I need to construct an xpath string to select all descendants of a certain table with these conditions: The table is a descendant of a form with a specific action attribute value. The selected descendants are text nodes. The text node content can only contain whitespace. It'll probably look something like: //form[@action = "submit.html"]//table//text()[ ...? ] Any tips would be appreciated. Thanks. Edit: For clarity, here is my current (working) compromise: function KillTextNodes(rootpath) { XPathIterate(rootpath + '//text()', function(node) { var tagname = node.parentNode.tagName; if (tagname != 'OPTION' && tagname != 'TH') Kill(node); }); }

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  • FOR loop performance in Javascript

    - by AndrewMcLagan
    As my research leads me to believe that for loops are the fastest iteration construct in javascript language. I was thinking that also declaring a conditional length value for the for loop would be faster... to make it clearer, which of the following do you think would be faster? Example ONE for(var i = 0; i < myLargeArray.length; i++ ) { console.log(myLargeArray[i]); } Example TWO var count = myLargeArray.length; for(var i = 0; i < count; i++ ) { console.log(myLargeArray[i]); } my logic follows that on each iteration in example one accessing the length of myLargeArray on each iteration is more computationally expensive then accessing a simple integer value as in example two?

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  • list permutations in haskell

    - by turingcomplete
    So I'm new to haskell and I've been playing with it for a while now. I want to get my function that outputs all list permutations to work. I have written 2 implementations, one works well, the other is giving me an error. Any help would be awesome. This is the first (working) implementation: permute [] = [[]] permute xs = [y| x <- xs, y <- map (x:) $ permute $ delete x xs] This one is giving me an error: permute [] = [[]] permute xs = map (\x -> map (x:) $ permute $ delete x xs) xs and here's the error message: Occurs check: cannot construct the infinite type: t0 = [t0] Expected type: [t0] Actual type: [[t0]] In the expression: map (x :) $ permute $ delete x xs In the first argument of `map', namely `(\ x -> map (x :) $ permute $ delete x xs)' I'd appreciate if someone could explain why I'm getting this error. Thanks

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  • GQL Query with __key__ in List of KEYs

    - by bossylobster
    In the GQL reference [1], it is encouraged to use the IN keyword with a list of values, and to construct a Key from hand the GQL query SELECT * FROM MyModel WHERE __key__ = KEY('MyModel', 'my_model_key') will succeed. However, using the code you would expect to work: SELECT * FROM MyModel WHERE __key__ IN (KEY('MyModel', 'my_model_key1'), KEY('MyModel', 'my_model_key2')) in the Datastore Viewer, there is a complaint of "Invalid GQL query string." What is the correct way to format such a query? [1] http://code.google.com/appengine/docs/python/datastore/gqlreference.html PS I know there are more efficient ways to do this in Python (without constructing a GQL query) and using the remote_api, but each call to the remote_api counts against quota. In an environment where quota is not (necessarily) free, quick and dirty queries are very helpful.

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  • Nested pound sign problem

    - by Ray Buechler
    I'm having an issue when I try to nest pound signs in my ColdFusion code. I keep getting the following error message: Invalid CFML construct found on line 57 at column 26. ColdFusion was looking at the following text: # Here is the code: <cfloop index="i" from="1" to="12"> <cfset needRecord.setNeed#i#(#form["need#i#"]#) /> </cfloop> If I run the loop outside the cfset tag like this: <cfloop index="i" from="1" to="12"> needRecord.setNeed#i#(#form["need#i#"]#) </cfloop> The code runs and generates what I would like to generate within the cfset tag. Any idea what I'm doing wrong? Any help would be greatly appreciated.

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  • How to email CLLocationCoordinate2D as a link

    - by lucasweb
    I am trying to emulate the Maps 'Share Location' via email functionality. I have the latitude and longitude of my location and am currently using it to display the location on a map via MKMapView. I also have functionality that composes an email from the app and I would like to include the location in it but can not figure out how to construct a link, using the longitude and latitude. I have seen other apps with apps with this functionality so I know it is possible. Any help would be much appreciated. Thanks in advance.

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  • Constructing a function call in C

    - by 0x6adb015
    Given that I have a pointer to a function (provided by dlsym() for example) and a linked list of typed arguments, how can I construct a C function call with those arguments? Example: struct param { enum type { INT32, INT64, STRING, BOOL } type; union { int i32; long long i64; char *str; bool b; } value; struct param *next; }; int call_this(int (*function)(), struct param *args) { int result; /* magic here that calls function(), which has a prototype of f(int, long long, char *, bool); , when args consist of a linked list of INT32, INT64, STRING, BOOL types. */ return result; } The OS is Linux. I would like the solution to be portable across MIPS, PPC and x86 (all 32 bits) architecture, using GCC as the compiler. Thanks!

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  • Getting Database Data to the client side.

    - by Toby Allen
    I'm sure this has been asked a million times, but what is the accepted approach to this? I have been writing php code for a while and up until recently I only copied+pasted javascript code, but now with help from YUI I've begun to understand javascript and want to use it more in an existing web app I have. I want to get various amounts of data from databases etc to the clientside javascript. I have access to this data in my php pages when loading. What is the correct way to get this data to my client side script. Generate clientside javascript in my php or smarty template files inserting the data where I need it? Use an Ajax call to retrieve the information I need from a php file - returning JSON data? Generate a JSON data construct of the data needed by the page and either return it via a script inclusion or dumping it to the generated page? Something really obvious I haven't thought of.

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  • WPF List of ViewModels bound to list of Model objects.

    - by Eric
    In the model, I have: public ObservableCollection<Item> Items { get; private set; } In the ViewModel, I have a corresponding list of ItemViewModels: public ObservableCollection<ItemViewModel> ItemViewModels ... In the XAML, I will bind (in this case a TreeView) to the ItemViewModels property. My question is, what goes in the "..." in the ViewModel shown above? I am hoping for a line or two of code to binds these two ObservableCollections (providing the type of the ViewModel to construct for each model object). However, what I'm fearing is necessary is a bunch of code to handle the Items.CollectionChanged event and manually updates the ItemViewModels list by constructing ViewModels as necessary. Thanks! Eric

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • The ** idiom in C++ for object construction

    - by bobobobo
    In a lot of C++ API'S (COM-based ones spring to mind) that make something for you, the pointer to the object that is constructed is usually required as a ** pointer (and the function will construct and init it for you) You usually see signatures like: HRESULT createAnObject( int howbig, Object **objectYouWantMeToInitialize ) ; -- but you seldom see the new object being passed as a return value. Besides people wanting to see error codes, what is the reason for this? Is it better to use the ** pattern rather than a returned pointer for simpler operations such as: wchar_t* getUnicode( const char* src ) ; Or would this better be written as: void getUnicode( const char* src, wchar_t** dst ) ; The most important thing I can think of is to remember to free it, and the ** way, for some reason, tends to remind me that I have to deallocate it as well.

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  • Push a variable into global scope?

    - by Spot
    We use instantiate and put system critical objects in $GLOBALS for easy access from anywhere (e.g. DB, Cache, User, etc.). We use $GLOBALS so much that it would (yes, really) drop the amount of code quite a bit if I could reference it like $G = &$GLOBALS for a shorthand call. The problem is that, per my experience and several hours of Googling, I have not found any construct in PHP which allows you to 'flag' a var as global, making $GLOBALS first class, and everything else second class. Am I missing something? Is this possible?

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  • Inspiration and influence of the else clause of loop statements?

    - by Aristide
    Python offers an optional loop-else clause which is executed if and only if the loop is not terminated by a break. (In other words, the condition fails for a while-loop or the iterator is exhausted for a for-loop.) Does this loop-else construct originate from another language? (Either theoretical or actually implemented.) Has it been taken up in any newer language? Maybe I should ask the former of Guido, but surely he is too busy for such a futile inquiry. ;-) Related discussion and examples: Pythonic ways to use ‘else’ in a for loop

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  • How to implement a C# interface in F#?

    - by Anton Andreev
    I would like to implement the following C# interface in F#: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Mono.Addins; [TypeExtensionPoint] public interface ISparqlCommand { string Name { get; } object Run(Dictionary<string, string> NamespacesDictionary, org.openrdf.repository.Repository repository, params object[] argsRest); } This is what I have tried, but it gives me: "Incomplete structured construct at or before this point in expression" #light module Module1 open System open System.Collections.Generic; type MyClass() = interface ISparqlCommand with member this.Name = "Finding the path between two tops in the Graph" member this.Run(NamespacesDictionary, repository, argsRest) = new System.Object What am I doing wrong? Maybe indentation is wrong?

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  • Postfix and right-associative operators in LR(0) parsers

    - by Ian
    Is it possible to construct an LR(0) parser that could parse a language with both prefix and postfix operators? For example, if I had a grammar with the + (addition) and ! (factorial) operators with the usual precedence then 1+3! should be 1 + 3! = 1 + 6 = 7, but surely if the parser were LR(0) then when it had 1+3 on the stack it would reduce rather than shift? Also, do right associative operators pose a problem? For example, 2^3^4 should be 2^(3^4) but again, when the parser have 2^3 on the stack how would it know to reduce or shift? If this isn't possible is there still a way to use an LR(0) parser, possibly by converting the input into Polish or Reverse Polish notation or adding brackets in the appropriate places? Would this be done before, during or after the lexing stage?

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  • Adding nodes to a global linked-list

    - by Zack
    I am attempting to construct my first linked list, and having read a basic introduction, have done the following. Firstly, declare a linked list node as: struct errorNode { uint8 error; struct errorNode* next; }; Secondly, define the first node globally as: struct errorNode errorList = {0, NULL}; This has been done to allow each of the libraries that make up my current project to insert errors into a common list. The function to do this is: void errorListWrite(uint8 error) { struct errorNode* newNode = malloc(sizeof(struct errorNode)); newNode->error = error; newNode->next = &errorList; errorList = *newNode; } Whilst this compiles without error, it does not function as expected. I thnk the problem is with the last two statements of the list write function, but I am unsure. A hint as to what I am doing wrong would be most appreciated.

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  • Image processing custom filter 7 by 7

    - by ladiesMan217
    Lets say I have a 7 by 7 neighborhood around a pixel that looks like this 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 and I wanna filter the above by replacing the pixel p by the average of those pixels whose value lie in the range -10<=p_value <=10. I am new to image processing and I think in this case p_value is 25 and around 25 that are many pixel values in that range but don't exactly know to construct a convolution filter out of it.

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  • Why isn't my IO executed in order?

    - by HaskellElephant
    Hi, I'm having some fun learning about the haskell IO. However in my recent exploration of it I have encountered some problems with IO not executing in order, even inside a do construct. In the following code I am just keeping track of what cards are left, where the card is a tuple of chars (one for suit and one for value) then the user is continously asked for wich cards have been played. I want the putStr to be executed between each input, and not at the very end like it is now. module Main where main = doLoop cards doLoop xs = do putStr $ show xs s <- getChar n <- getChar doLoop $ remove (s,n) xs suits = "SCDH" vals = "A23456789JQK" cards = [(s,n) | s <- suits, n <- vals] type Card = (Char,Char) remove :: Card -> [Card] -> [Card] remove card xs = filter (/= card) xs

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  • How to create a bash function with variable parameters/arguments to grep several keywords/tags

    - by CornSmith
    I'm using the :!grep "tag1" filename | grep "tag2" filename | grep -n "tag3 or more" filename command in vim to search for my code snippets based on their tags (a simple comment at the top of a snippet) in one big file. I use snippets to remember tricky things. This is painful to write out each time. I'd like to make an alias, or function to do something like this: :!greptag tag1 tag2 ... tag39 And it should search the current doc and return the lines with all the tags on them. Vim is set to interactive shell mode so that it can parse my bashrc for aliases/functions. set shellcmdflag=-ic How can I construct a function that allows for variable arguments like this in bash?

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  • whats wrong with this piece of code for saving contacts

    - by Shadow
    Hi, i am using the latest Nokia Qt SDK. i have tried to add the contacts, its not getting added.. what is missing here.. // Construct contact manager for default contact backend QContactManager* cm = new QContactManager("simulator"); // QContactManager* cm = new QContactManager("memory"); // i tried this, its also not working // Create example contact QContact example; // Add contact name QContactName name; name.setFirstName("John"); name.setLastName("Doe"); example.saveDetail(&name); // Add contact email address //QContactEmailAddress email; // email.setContexts(QContactDetail::ContextHome); //email.setEmailAddress(“[email protected]”); // example.saveDetail(&email); // Finally, save the contact details cm->saveContact(&example); delete cm; Thanks

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  • listView.setAdapter doesn't work

    - by Bowiz2
    I have a listview called quotesList, and I am trying to use an adapter to put information in it. Here is my code: ListView listView = (ListView) findViewById(R.id.quotesList); String[]values={"Android","iOS","Windows Phone","Other Stuff"}; ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, android.R.id.text1,values); listView.setAdapter(adapter); The only error that Eclipse shows is in the listView.setAdapter(adapter) line. The bold represents where the red squiggly is. Syntax error on token "adapter", VariableDeclaratorId expected after this token The period after listView gives an error as well, but I'm pretty sure its just related to the other error, as its a syntax error. Syntax error on token(s), misplaced construct(s) Thanks in advance!

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  • C#: How to constuct a variable from another variables

    - by ozzwanted
    How to construct new variable in C#. I mean, to have sth like this public void updateXXX(string endingOfVariable, int newValue) { this.textBox_{endingOfVariable} = newValue; } This is implemented in Php: $a = 'var'; $b = 'iable'; $variable = 'var'; echo ${$a.$b}; But maybe it is possible in C#. The problem is that - I created ~500 textBoxes in C# Windows Form, and if I want to set a value, I need to build a switch() {case:; } statment with 500's cases.

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  • Is Android IPC plumbing exposed in any official and/or supported way?

    - by mathrick
    I'm interested in knowing how much the IPC mechanisms are meant to be exposed to the outside world. That is, if I wanted to impersonate a dalvik VM instance without having my app actually written in Java, am I allowed to do so, or will the protocol change the next time I look away from the screen? If it's allowed, what are the stability guarantees or lack thereof? Is there anything like documentation, or am I supposed just to read the fine sources on android.git.kernel.org? The purpose of it all would be to write apps in !Java languages while retaining the ability to construct GUIs. I don't care or mind if the code is technically inside a dalvik process as a JNI callout, what I'm interested in is "if I'm really good at pretending I'm Java over the wire, can I do everything actual Java code can? Or is there something that's only available as Java bytecode and nothing else?"

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