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  • when to make a method static

    - by Don
    Hi, I'd like to know how people decide whether to define a method as static. I'm aware that a method can only be defined as static if it doesn't require access to instance fields. So lets say we have a method that does not access instance fields, do you always define such a method as static, or only if you need to call it statically (without a reference to an instance). Perhaps another way of asking the same question, is whether you use static or non-static as the default? Thanks, Don

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  • coding on back button of navigation based application??

    - by hemant
    In one view during a function call i am assigning 1 to a flag...when i navigate back to previous view i want the the flag value to be retained to that view...how cAn i do coding on the button that appears on the screen to navigate back to the previous screen might be able to do it or is there any better solution???

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  • iPhone Launch Image zoom animation not working on physical device

    - by user341542
    I have developed an iPhone app with a launch image. When starting the app in the simulator, the image zooms in as expected. However, when the app is deployed to my physical device, the zoom animation is very short and sometimes completes instantaneously. I'm sure it's nothing to do with my app start up as I put a sleep call in applicationDidFinishLoading to slow it down and this occurs after the zoom animation has completed.

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  • Unable to open images with Python's Image.open()

    - by ensnare
    My code reads: import Image def generateThumbnail(self, width, height): """ Generates thumbnails for an image """ im = Image.open(self._file) When I call this function, I get an error: ? AttributeError: type object 'Image' has no attribute 'open' However in the console: import Image im = Image.open('test.jpg') I have no problem. Any ideas? Thanks!

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  • Are comonads a good fit for modeling the Wumpus world?

    - by Tim Stewart
    I'm trying to find some practical applications of a comonad and I thought I'd try to see if I could represent the classical Wumpus world as a comonad. I'd like to use this code to allow the Wumpus to move left and right through the world and clean up dirty tiles and avoid pits. It seems that the only comonad function that's useful is extract (to get the current tile) and that moving around and cleaning tiles would not use be able to make use of extend or duplicate. I'm not sure comonads are a good fit but I've seen a talk (Dominic Orchard: A Notation for Comonads) where comonads were used to model a cursor in a two-dimensional matrix. If a comonad is a good way of representing the Wumpus world, could you please show where my code is wrong? If it's wrong, could you please suggest a simple application of comonads? module Wumpus where -- Incomplete model of a world inhabited by a Wumpus who likes a nice -- tidy world but does not like falling in pits. import Control.Comonad -- The Wumpus world is made up of tiles that can be in one of three -- states. data Tile = Clean | Dirty | Pit deriving (Show, Eq) -- The Wumpus world is a one dimensional array partitioned into three -- values: the tiles to the left of the Wumpus, the tile occupied by -- the Wumpus, and the tiles to the right of the Wumpus. data World a = World [a] a [a] deriving (Show, Eq) -- Applies a function to every tile in the world instance Functor World where fmap f (World as b cs) = World (fmap f as) (f b) (fmap f cs) -- The Wumpus world is a Comonad instance Comonad World where -- get the part of the world the Wumpus currently occupies extract (World _ b _) = b -- not sure what this means in the Wumpus world. This type checks -- but does not make sense to me. extend f w@(World as b cs) = World (map world as) (f w) (map world cs) where world v = f (World [] v []) -- returns a world in which the Wumpus has either 1) moved one tile to -- the left or 2) stayed in the same place if the Wumpus could not move -- to the left. moveLeft :: World a -> World a moveLeft w@(World [] _ _) = w moveLeft (World as b cs) = World (init as) (last as) (b:cs) -- returns a world in which the Wumpus has either 1) moved one tile to -- the right or 2) stayed in the same place if the Wumpus could not move -- to the right. moveRight :: World a -> World a moveRight w@(World _ _ []) = w moveRight (World as b cs) = World (as ++ [b]) (head cs) (tail cs) initWorld = World [Dirty, Clean, Dirty] Dirty [Clean, Dirty, Pit] -- cleans the current tile cleanTile :: Tile -> Tile cleanTile Dirty = Clean cleanTile t = t Thanks!

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  • F# mutual recursion between modules

    - by rwallace
    For recursion in F#, existing documentation is clear about how to do it in the special case where it's just one function calling itself, or a group of physically adjacent functions calling each other. But in the general case where a group of functions in different modules need to call each other, how do you do it?

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  • Determining if Memory Pointer is Valid - C++

    - by Jim Fell
    It has been my observation that if free( ptr ) is called where ptr is not a valid pointer to system-allocated memory, an access violation occurs. Let's say that I call free like this: LPVOID ptr = (LPVOID)0x12345678; free( ptr ); This will most definitely cause an access violation. Is there a way to test that the memory location pointed to by ptr is valid system-allocated memory? It seems to me that the the memory management part of the Windows OS kernel must know what memory has been allocated and what memory remains for allocation. Otherwise, how could it know if enough memory remains to satisfy a given request? (rhetorical) That said, it seems reasonable to conclude that there must be a function (or set of functions) that would allow a user to determine if a pointer is valid system-allocated memory. Perhaps Microsoft has not made these functions public. If Microsoft has not provided such an API, I can only presume that it was for an intentional and specific reason. Would providing such a hook into the system prose a significant threat to system security? Situation Report Although knowing whether a memory pointer is valid could be useful in many scenarios, this is my particular situation: I am writing a driver for a new piece of hardware that is to replace an existing piece of hardware that connects to the PC via USB. My mandate is to write the new driver such that calls to the existing API for the current driver will continue to work in the PC applications in which it is used. Thus the only required changes to existing applications is to load the appropriate driver DLL(s) at startup. The problem here is that the existing driver uses a callback to send received serial messages to the application; a pointer to allocated memory containing the message is passed from the driver to the application via the callback. It is then the responsibility of the application to call another driver API to free the memory by passing back the same pointer from the application to the driver. In this scenario the second API has no way to determine if the application has actually passed back a pointer to valid memory.

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  • jQuery treat hover on two elements as one elements

    - by davewilly
    I have an image map which I have overlaid with some markers in the form of anchors. I currently have a hover trigger on each image map area and the associated anchor - as shown in screen shot I need to treat these two elements as one, as currently when mouse is moved out of one onto the other it calls .hover() and callback again. I want to call hover callback only when mouse is moved out of either elements.

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  • Re-define File::dirname ruby method

    - by jrhicks
    I'm trying to redefine the File.dirname method to first change %20s to spaces. But the following gives me an error class File old_dirname = instance_method(:dirname) define_method(:dirname) { |s| s = s.gsub("%20"," ") old_dirname.bind(self).call(s) } end This trhows a NameError exception: undefined method 'dirname' for class 'File' What is the right way to do this?

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  • Function Overloading

    - by Sanju
    Let us suppose i have these three methods defined: int F1(int, int); int F1(float, float); Float F1(int, int); and i am calling method F1 here: Console.writeline(F1(5,6).ToString())); Which method it will call and why?

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  • Can ggplot2 work with R's canvas backend

    - by Casbon
    Having installed canvas from here http://www.rforge.net/canvas/files/ I try to plot: > canvas('test.js') > qplot(rnorm(100), geom='histogram') stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this. Error in grid.Call.graphics("L_setviewport", pvp, TRUE) : Non-finite location and/or size for viewport >

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  • Calling CryptUIWizDigitalSign from .NET on x64

    - by Joe Kuemerle
    I am trying to digitally sign files using the CryptUIWizDigitalSign function from a .NET 2.0 application compiled to AnyCPU. The call works fine when running on x86 but fails on x64, it also works on an x64 OS when compiled to x86. Any idea on how to better marshall or call from x64? The Win32exception returned is "Error encountered during digital signing of the file ..." with a native error code of -2146762749. The relevant portion of the code are: [StructLayout(LayoutKind.Sequential)] public struct CRYPTUI_WIZ_DIGITAL_SIGN_INFO { public Int32 dwSize; public Int32 dwSubjectChoice; [MarshalAs(UnmanagedType.LPWStr)] public string pwszFileName; public Int32 dwSigningCertChoice; public IntPtr pSigningCertContext; [MarshalAs(UnmanagedType.LPWStr)] public string pwszTimestampURL; public Int32 dwAdditionalCertChoice; public IntPtr pSignExtInfo; } [DllImport("Cryptui.dll", CharSet=CharSet.Unicode, SetLastError=true)] public static extern bool CryptUIWizDigitalSign(int dwFlags, IntPtr hwndParent, string pwszWizardTitle, ref CRYPTUI_WIZ_DIGITAL_SIGN_INFO pDigitalSignInfo, ref IntPtr ppSignContext); CRYPTUI_WIZ_DIGITAL_SIGN_INFO digitalSignInfo = new CRYPTUI_WIZ_DIGITAL_SIGN_INFO(); digitalSignInfo = new CRYPTUI_WIZ_DIGITAL_SIGN_INFO(); digitalSignInfo.dwSize = Marshal.SizeOf(digitalSignInfo); digitalSignInfo.dwSubjectChoice = 1; digitalSignInfo.dwSigningCertChoice = 1; digitalSignInfo.pSigningCertContext = pSigningCertContext; digitalSignInfo.pwszTimestampURL = timestampUrl; digitalSignInfo.dwAdditionalCertChoice = 0; digitalSignInfo.pSignExtInfo = IntPtr.Zero; digitalSignInfo.pwszFileName = filepath; CryptUIWizDigitalSign(1, IntPtr.Zero, null, ref digitalSignInfo, ref pSignContext)); And here is how the SigningCertContext is retrieved (minus various error handling) public IntPtr GetCertContext(String pfxfilename, String pswd) IntPtr hMemStore = IntPtr.Zero; IntPtr hCertCntxt = IntPtr.Zero; IntPtr pProvInfo = IntPtr.Zero; uint provinfosize = 0; try { byte[] pfxdata = PfxUtility.GetFileBytes(pfxfilename); CRYPT_DATA_BLOB ppfx = new CRYPT_DATA_BLOB(); ppfx.cbData = pfxdata.Length; ppfx.pbData = Marshal.AllocHGlobal(pfxdata.Length); Marshal.Copy(pfxdata, 0, ppfx.pbData, pfxdata.Length); hMemStore = Win32.PFXImportCertStore(ref ppfx, pswd, CRYPT_USER_KEYSET); pswd = null; if (hMemStore != IntPtr.Zero) { Marshal.FreeHGlobal(ppfx.pbData); while ((hCertCntxt = Win32.CertEnumCertificatesInStore(hMemStore, hCertCntxt)) != IntPtr.Zero) { if (Win32.CertGetCertificateContextProperty(hCertCntxt, CERT_KEY_PROV_INFO_PROP_ID, IntPtr.Zero, ref provinfosize)) pProvInfo = Marshal.AllocHGlobal((int)provinfosize); else continue; if (Win32.CertGetCertificateContextProperty(hCertCntxt, CERT_KEY_PROV_INFO_PROP_ID, pProvInfo, ref provinfosize)) break; } } finally { if (pProvInfo != IntPtr.Zero) Marshal.FreeHGlobal(pProvInfo); if (hMemStore != IntPtr.Zero) Win32.CertCloseStore(hMemStore, 0); } return hCertCntxt; }

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  • Django model help

    - by dotty
    Does anyone have any clue why this doesn't work as expected. If i use the python shell and do team.game_set or team.games It returns an error AttributeError: 'Team' object has no attribute 'game' If i create a Game object and call game.home_team it returns the correct team object Heres my model class Team(models.Model): name = models.CharField(blank=True, max_length=100) class Game(models.Model): home_team = models.ForeignKey(Team, related_name="home_team")

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  • XMLEncoder in java for serialization

    - by tom
    Im just wondering how i use xmlencoder to serialize ArrayList where foo is my own made class. Do i have to do anything in particular, ie define my own xml structure first and then call toString on each value in my list and write it out? Can anyone point me to a good tutorial? http://java.sun.com/products/jfc/tsc/articles/persistence4/ Thats what i have been looking at but it doesnt seem to mention what to do with non library classes. Thanks

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  • How can c let a function declaration with any parameter type ?

    - by kamil çakir
    I forgot to write void parameter but it works the i put void it gives error it lets this: print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i it says"previos implicit declaration was here " (means the call in main) void print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i

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  • How can c let a function declaration with any parameter type ?

    - by kamil çakir
    it lets this function declaration print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i gives error in this situation 44 C:\Users.. previous implicit declaration of 'print' was here (print(size,table); call in main) void print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i

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  • Damaged data when gzipping

    - by RadiantHeart
    This is the script I hva written for gzipping content on my site, which is located in 'gzip.php'. The way i use it is that on pages where I want to enable gzipping i include the file at the top and at the bottom i call the output function like this: print_gzipped_page('javascript') If the file is a css-file i use 'css' as the $type-argument and if its a php file i call the function without declaring any arguments. The script works fine in all browsers except Opera which gives an error saying it could not decode the page due to damaged data. Can anyone tell me what I have done wrong? <?php function print_gzipped_page($type = false) { if(headers_sent()){ $encoding = false; } elseif( strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'x-gzip') !== false ){ $encoding = 'x-gzip'; } elseif( strpos($_SERVER['HTTP_ACCEPT_ENCODING'],'gzip') !== false ){ $encoding = 'gzip'; } else{ $encoding = false; } if ($type!=false) { $type_header_array = array("css" => "Content-Type: text/css", "javascript" => "Content-Type: application/x-javascript"); $type_header = $type_header_array[$type]; } $contents = ob_get_contents(); ob_end_clean(); $etag = '"' . md5($contents) . '"'; $etag_header = 'Etag: ' . $etag; header($etag_header); if ($type!=false) { header($type_header); } if (isset($_SERVER['HTTP_IF_NONE_MATCH']) and $_SERVER['HTTP_IF_NONE_MATCH']==$etag) { header("HTTP/1.1 304 Not Modified"); exit(); } if($encoding){ header('Content-Encoding: '.$encoding); print("\x1f\x8b\x08\x00\x00\x00\x00\x00"); $size = strlen($contents); $contents = gzcompress($contents, 9); $contents = substr($contents, 0, $size); } echo $contents; exit(); } ob_start(); ob_implicit_flush(0); ?> Additional info: The script works if the length og the document beeing compressed is only 10-15 characters.

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