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  • Question about array subscripting in C#

    - by Michael J
    Back in the old days of C, one could use array subscripting to address storage in very useful ways. For example, one could declare an array as such. This array represents an EEPROM image with 8 bit words. BYTE eepromImage[1024] = { ... }; And later refer to that array as if it were really multi-dimensional storage BYTE mpuImage[2][512] = eepromImage; I'm sure I have the syntax wrong, but I hope you get the idea. Anyway, this projected a two dimension image of what is really single dimensional storage. The two dimensional projection represents the EEPROM image when loaded into the memory of an MPU with 16 bit words. In C one could reference the storage multi-dimensionaly and change values and the changed values would show up in the real (single dimension) storage almost as if by magic. Is it possible to do this same thing using C#? Our current solution uses multiple arrays and event handlers to keep things synchronized. This kind of works but it is additional complexity that we would like to avoid if there is a better way.

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  • Question and Answers form & controller problem

    - by user285245
    Hi, I have a Question table and an Answers table linked by questionID (1 to many). I'd like to be able to update both table from the one form. I can easily add a question but to have it also add the answers (into their own recordsets) is causing a headache. how do I set my form up to allow for the answers to be created and also what do I do in the Controller. Any help would be gratefully appreciated as I've not been able to locate any good examples on the web. thanks in advance.

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  • Java print binary number using bit-wise operator

    - by user69514
    Hi I am creating a method that will take a number and print it along with its binary representation. The problems is that my method prints all 0's for any positive number, and all 1's for any negative number private static void display( int number ){ System.out.print(number + "\t"); int mask = 1 << 31; for(int i=1; i<=32; i++) { if( (mask & number) != 0 ) System.out.print(1); else System.out.print(0); if( (i % 4) == 0 ) System.out.print(" "); } }

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  • Beginner SQL question(s)

    - by unit
    I am two months in to an intro sql course, it's late at night, and I am drawing a blank. I have two tables, one customers, and one orders. I have to increase any customers credit limit by twenty five percent for all customers who have made two or more orders in which each order is more than the amount of 250.00. I get how to UPDATE CreditLimit * 1.25 and Cust with an order 250, but how the hell do I get it to check if they have made two orders over 250? Second question, we are just starting to take subqueries, and I am having a difficult time getting it into my skull. Another question posed by the prof of our class is to increase the credit limit of a customer who has an order that exceeds their credit limit. (Credit limit is on a customers table, order and amount are on an orders table). I then take that customer and UPDATE his CreditLimit +1000. Thanks for any help.

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  • Flash Player error logs on Mac OS X

    - by paleozogt
    I'm on Mac OS X 10.5.8 running Flash Player 10,0,32,18. Flash Player is dumping giant amounts of error logging into the system log (stuff like "bit length overflow" and "code 0 bits 6-7"). Here's a tiny sampling: Oct 14 13:09:41 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:09:41 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 6 bits 6->7 Oct 14 13:09:41 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:09:41 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 5 bits 6->7 Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 6 bits 6->7 Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 5 bits 6->7 Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:09:55 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 0 bits 6->7 Oct 14 13:10:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 4 bits 6->7 Oct 14 13:10:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 12 bits 6->7 Oct 14 13:10:20 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:20 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 6 bits 6->7 Oct 14 13:10:20 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:20 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 5 bits 6->7 Oct 14 13:10:21 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:21 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 0 bits 6->7 Oct 14 13:10:21 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:21 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 12 bits 6->7 Oct 14 13:10:31 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:31 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 7 bits 6->7 Oct 14 13:10:31 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:10:31 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 12 bits 6->7 Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 3 bits 6->7 Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 4 bits 6->7 Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 3 bits 7->6 Oct 14 13:11:06 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 4 bits 5->6 Oct 14 13:11:07 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:07 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 3 bits 6->7 Oct 14 13:11:07 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:07 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 3 bits 6->7 Oct 14 13:11:15 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:15 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 3 bits 6->7 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 7 bits 6->7 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 0 bits 4->5 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 14 bits 4->5 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 10 bits 5->4 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: code 4 bits 5->4 Oct 14 13:11:26 thorst-2 [0x0-0x58058].com.adobe.flash-10.0[2416]: bit length overflow Any ideas on what this may be about?

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  • RESTful services architecture question

    - by abovesun
    This is question more about service architecture strategy, we are building big web system based on rest services on back end. And we are currently trying to build some standard internal to follow while developing rest services. Some queries returns list of entities, for example lets consider we have image galleries retrieving service: /gell_all_galeries, returning next response: <galleries> <gallery> <id>some_gallery_id</id> <name>my photos</name> <photos> <photo> <id>123</id> <name>my photo</name> <location>http://mysite/photo/show/123</location> ...... <author> <id>some_id</id> <name>some name</name> ....... <author> </photo> <photo> ..... </photo> <photo> ..... </photo> <photo> ..... </photo> <photo> ..... </photo> </photos> </gallery> <gallery> .... </gallery> <gallery> .... </gallery> <gallery> .... </gallery> <gallery> .... </gallery> </galleries> As you see here, response quite big and heavy, and not always we need such deep info level. Usual solution is to use or http://ru.wikipedia.org/wiki/Atom elements for each gallery instead of full gallery data: <galleries> <gallery> <id>some_gallery_id</id> <link href="http://mysite/gallery/some_gallery_id"/> </gallery> <gallery> <id>second_gallery_id</id> <link href="http://mysite/gallery/second_gallery_id"/> </gallery> <gallery> .... </gallery> <gallery> .... </gallery> <gallery> .... </gallery> <gallery> .... </gallery> </galleries> The first question, is next: maybe instead we shouldn't even use and types, and just use generic and for all resources that return list objects: <list> <item><link href="http://mysite/gallery/some_gallery_id"/></item> <item><link href="http://mysite/gallery/other_gallery_id"/></item> <item>....</item> </list> And the second question, after user try to retrieve info about some concrete gallery, he'll use for example http://mysite/gallery/some_gallery_id link, what should he see as results? Should it be: <gallery> <id>some_gallery_id</id> <name>my photos</name> <photos> <photo> <id>123</id> <name>my photo</name> <location>http://mysite/photo/show/123</location> ...... <author> <id>some_id</id> <name>some name</name> ....... <author> </photo> <photo> ..... </photo> <photo> ..... </photo> <photo> ..... </photo> <photo> ..... </photo> </photos> </gallery> or : <gallery> <id>some_gallery_id</id> <name>my photos</name> <photos> <photo><link href="http://mysite/photo/11111"/></photo> <photo><link href="http://mysite/photo/22222"/></photo> <photo><link href="http://mysite/photo/33333"/> </photo> <photo> ..... </photo> </photos> </gallery> or <gallery> <id>some_gallery_id</id> <name>my photos</name> <photos> <photo> <link href="http://mysite/photo/11111"/> <author> <link href="http://mysite/author/11111"/> </author> </photo> <photo> <link href="http://mysite/photo/22222"/> <author> <link href="http://mysite/author/11111"/> </author> </photo> <photo> <link href="http://mysite/photo/33333"/> <author> <link href="http://mysite/author/11111"/> </author> </photo> <photo> ..... </photo> </photos> </gallery> I mean if we use link instead of full object info, how deep we should go there? Should I show an author inside photo and so on. Probably my question ambiguous, but what I'm trying to do is create general strategy in such cases for all team members to follow in future.

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  • How do I read 64-bit Registry values from VBScript running as a an msi post-installation task?

    - by Joergen Bech
    I need to read the location of the Temporary ASP.NET Files folder from VBScript as part of a post-installation task in an installer created using a Visual Studio 2008 deployment project. I thought I would do something like this: Set oShell = CreateObject("Wscript.Shell") strPath = oShell.RegRead("HKLM\SOFTWARE\Microsoft\ASP.NET\2.0.50727.0\Path") and then concatenate strPath with "\Temporary ASP.NET Files" and be done with it. On an x64 system, however, I am getting the value from the WOW6432Node (HKLM\SOFTWARE\Wow6432Node\Microsoft\ASP.NET\2.0.50727.0), which gives me the 32-bit framework path (C:\Windows\Microsoft.NET\Framework\v2.0.50727), but on an x64 system, I actually want the 64-bit path, i.e. C:\Windows\Microsoft.NET\Framework64\v2.0.50727. I understand that this happens because the .vbs file is run using the 32-bit script host due to the parent process (the installer) being 32-bit itself. How can I run the script using the 64-bit script host - or - how can I read the 64-bit values even if the script is run using the 32-bit script host?

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  • Ever any performance different between Java >> and >>> right shift operators?

    - by Sean Owen
    Is there ever reason to think the (signed) and (unsigned) right bit-shift operators in Java would perform differently? I can't detect any difference on my machine. This is purely an academic question; it's never going to be the bottleneck I'm sure. I know: it's best to write what you mean foremost; use for division by 2, for example. I assume it comes down to which architectures have which operations implemented as an instruction.

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  • Java bitshift strangeness

    - by Martin
    Java has 2 bitshift operators for right shifts: >> shifts right, and is dependant on the sign bit for the sign of the result >>> shifts right and shifts a zero into leftmost bits http://java.sun.com/docs/books/tutorial/java/nutsandbolts/op3.html This seems fairly simple, so can anyone explain to me why this code, when given a value of -128 for bar, produces a value of -2 for foo: byte foo = (byte)((bar & ((byte)-64)) >>> 6); What this is meant to do is take an 8bit byte, mask of the leftmost 2 bits, and shift them into the rightmost 2 bits. Ie: initial = 0b10000000 (-128) -64 = 0b11000000 initial & -64 = 0b10000000 0b10000000 >>> 6 = 0b00000010 The result actually is -2, which is 0b11111110 Ie. 1s rather than zeros are shifted into left positions

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  • C# int to byte[]

    - by Petoj
    If I need to convert an int to byte[] I could use Bitconvert.GetBytes(). But if I should follow this: An XDR signed integer is a 32-bit datum that encodes an integer in the range [-2147483648,2147483647]. The integer is represented in two's complement notation. The most and least significant bytes are 0 and 3, respectively. Integers are declared as follows: Taken from RFC1014 3.2. What method should I use then if there is no method to do this? How would it look like if you write your own? I don't understand the text 100% so I can't implement it on my own.

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  • Alternative to BitConverter.ToInt32

    - by MusiGenesis
    I'm using BitConverter.ToInt32 to pack 3 byte values into an int, like so: byte R = 0; byte G = 0; byte B = 0; int i = BitConverter.ToInt32(new byte[] { R, G, B, 0 }, 0); Is there a faster way to do this that doesn't involve the creation of a new int each time? Getting the bytes out of an int is easy: int i = 34234; byte B = (byte)(i >> 0); byte G = (byte)(i >> 8); byte R = (byte)(i >> 16); Is there a simple way to reverse this process and use bit-shifting to write the RGB bytes back over an existing int?

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  • How do I create an 8-bit PNG with transparency from an NSBitmapImageRep?

    - by Rob Keniger
    I have a 32-bit NSBitmapImageRep which has an alpha channel with essentially 1-bit values (the pixels are either on or off). I want to save this bitmap to an 8-bit PNG file with transparency. If I use the -representationUsingType:properties: method of NSBitmapImageRep and pass in NSPNGFileType, a 32-bit PNG is created, which is not what I want. I know that 8-bit PNGs can be read, they open in Preview with no problems, but is it possible to write this type of PNG file using any built-in Mac OS X APIs? I'm happy to drop down to Core Image or even QuickTime if necessary. A cursory examination of the CGImage docs didn't reveal anything obvious. EDIT: I've started a bounty on this question, if someone can provide working source code that takes a 32-bit NSBitmapImageRep and writes a 256-color PNG with 1-bit transparency, it's yours.

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  • DataType for storing a long serial number (10 bytes)

    - by CrimsonX
    We have a device which has a 10 byte serial number which must be read into our application and stored into a .net datatype. In the device it is stored as an unsigned 10-byte (80-bit) number. I don't expect we will be performing any mathematical operations on this number, but only displaying it to the user. The .NET framework doesn't have a built in UNIT128 to store this datatype. My suggestion for storing this datatype is to create a 10 element byte array and read in the data into this array. Are there any better solutions to this problem? Note: I have seen in this question that a GUID is a 128 byte signed integer, but it seems like a bad idea to use a GUID in this fashion. Any other suggestions?

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  • Extracting rightmost N bits of an integer

    - by srandpersonia
    In the yester Code Jam Qualification round http://code.google.com/codejam/contest/dashboard?c=433101#s=a&a=0 , there was a problem called Snapper Chain. From the contest analysis I came to know the problem requires bit twiddling stuff like extracting the rightmost N bits of an integer and checking if they all are 1. I saw a contestant's(Eireksten) code which performed the said operation like below: (((K&(1<<N)-1))==(1<<N)-1) I couldn't understand how this works. What is the use of -1 there in the comparison?. If somebody can explain this, it would be very much useful for us rookies. Also, Any tips on identifying this sort of problems would be much appreciated. I used a naive algorithm to solve this problem and ended up solving only the smaller data set.(It took heck of a time to compile the larger data set which is required to be submitted within 8 minutes.). Thanks in advance.

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  • Representing a very large array of bits in little memory

    - by user614624
    Hello, I would like to represent a structure containing 250 M states(1 bit each) somehow into as less memory as possible (100 k maximum). The operations on it are set/get. I cold not say that it's dense or sparse, it may vary. The language I want to use is C. I looked at other threads here to find something suitable also. A probabilistic structure like Bloom filter for example would not fit because of the possible false answers. Any suggestions please?

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  • Core Data Model Design Question - Changing "Live" Objects also Changes Saved Objects

    - by mwt
    I'm working on my first Core Data project (on iPhone) and am really liking it. Core Data is cool stuff. I am, however, running into a design difficulty that I'm not sure how to solve, although I imagine it's a fairly common situation. It concerns the data model. For the sake of clarity, I'll use an imaginary football game app as an example to illustrate my question. Say that there are NSMO's called Downs and Plays. Plays function like templates to be used by Downs. The user creates Plays (for example, Bootleg, Button Hook, Slant Route, Sweep, etc.) and fills in the various properties. Plays have a to-many relationship with Downs. For each Down, the user decides which Play to use. When the Down is executed, it uses the Play as its template. After each down is run, it is stored in history. The program remembers all the Downs ever played. So far, so good. This is all working fine. The question I have concerns what happens when the user wants to change the details of a Play. Let's say it originally involved a pass to the left, but the user now wants it to be a pass to the right. Making that change, however, not only affects all the future executions of that Play, but also changes the details of the Plays stored in history. The record of Downs gets "polluted," in effect, because the Play template has been changed. I have been rolling around several possible fixes to this situation, but I imagine the geniuses of SO know much more about how to handle this than I do. Still, the potential fixes I've come up with are: 1) "Versioning" of Plays. Each change to a Play template actually creates a new, separate Play object with the same name (as far as the user can tell). Underneath the hood, however, it is actually a different Play. This would work, AFAICT, but seems like it could potentially lead to a wild proliferation of Play objects, esp. if the user keeps switching back and forth between several versions of the same Play (creating object after object each time the user switches). Yes, the app could check for pre-existing, identical Plays, but... it just seems like a mess. 2) Have Downs, upon saving, record the details of the Play they used, but not as a Play object. This just seems ridiculous, given that the Play object is there to hold those just those details. 3) Recognize that Play objects are actually fulfilling 2 functions: one to be a template for a Down, and the other to record what template was used. These 2 functions have a different relationship with a Down. The first (template) has a to-many relationship. But the second (record) has a one-to-one relationship. This would mean creating a second object, something like "Play-Template" which would retain the to-many relationship with Downs. Play objects would get reconfigured to have a one-to-one relationship with Downs. A Down would use a Play-Template object for execution, but use the new kind of Play object to store what template was used. It is this change from a to-many relationship to a one-to-one relationship that represents the crux of the problem. Even writing this question out has helped me get clearer. I think something like solution 3 is the answer. However if anyone has a better idea or even just a confirmation that I'm on the right track, that would be helpful. (Remember, I'm not really making a football game, it's just faster/easier to use a metaphor everyone understands.) Thanks.

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  • iPhone SDK / Objective C Syntax Question

    - by Koppo
    To all, I was looking at the sample project from http://iphoneonrails.com/ and I saw they took the NSObject class and added methods to it for the SOAP calls. Their sample project can be downloaded from here http://iphoneonrails.com/downloads/objective_resource-1.01.zip. My question is related to my lack of knowledge on the following syntax as I haven't seen it yet in a iPhone project. There is a header file called NSObject+ObjectiveResource.h where they declare and change NSObject to have extra methods for this project. Is the "+ObjectiveResource.h" in the name there a special syntax or is that just the naming convention of the developers. Finally inside the class NSObject we have the following #import <Foundation/Foundation.h> @interface NSObject (ObjectiveResource) // Response Formats typedef enum { XmlResponse = 0, JSONResponse, } ORSResponseFormat; // Resource configuration + (NSString *)getRemoteSite; + (void)setRemoteSite:(NSString*)siteURL; + (NSString *)getRemoteUser; + (void)setRemoteUser:(NSString *)user; + (NSString *)getRemotePassword; + (void)setRemotePassword:(NSString *)password; + (SEL)getRemoteParseDataMethod; + (void)setRemoteParseDataMethod:(SEL)parseMethod; + (SEL) getRemoteSerializeMethod; + (void) setRemoteSerializeMethod:(SEL)serializeMethod; + (NSString *)getRemoteProtocolExtension; + (void)setRemoteProtocolExtension:(NSString *)protocolExtension; + (void)setRemoteResponseType:(ORSResponseFormat) format; + (ORSResponseFormat)getRemoteResponseType; // Finders + (NSArray *)findAllRemote; + (NSArray *)findAllRemoteWithResponse:(NSError **)aError; + (id)findRemote:(NSString *)elementId; + (id)findRemote:(NSString *)elementId withResponse:(NSError **)aError; // URL construction accessors + (NSString *)getRemoteElementName; + (NSString *)getRemoteCollectionName; + (NSString *)getRemoteElementPath:(NSString *)elementId; + (NSString *)getRemoteCollectionPath; + (NSString *)getRemoteCollectionPathWithParameters:(NSDictionary *)parameters; + (NSString *)populateRemotePath:(NSString *)path withParameters:(NSDictionary *)parameters; // Instance-specific methods - (id)getRemoteId; - (void)setRemoteId:(id)orsId; - (NSString *)getRemoteClassIdName; - (BOOL)createRemote; - (BOOL)createRemoteWithResponse:(NSError **)aError; - (BOOL)createRemoteWithParameters:(NSDictionary *)parameters; - (BOOL)createRemoteWithParameters:(NSDictionary *)parameters andResponse:(NSError **)aError; - (BOOL)destroyRemote; - (BOOL)destroyRemoteWithResponse:(NSError **)aError; - (BOOL)updateRemote; - (BOOL)updateRemoteWithResponse:(NSError **)aError; - (BOOL)saveRemote; - (BOOL)saveRemoteWithResponse:(NSError **)aError; - (BOOL)createRemoteAtPath:(NSString *)path withResponse:(NSError **)aError; - (BOOL)updateRemoteAtPath:(NSString *)path withResponse:(NSError **)aError; - (BOOL)destroyRemoteAtPath:(NSString *)path withResponse:(NSError **)aError; // Instance helpers for getting at commonly used class-level values - (NSString *)getRemoteCollectionPath; - (NSString *)convertToRemoteExpectedType; //Equality test for remote enabled objects based on class name and remote id - (BOOL)isEqualToRemote:(id)anObject; - (NSUInteger)hashForRemote; @end What is the "ObjectiveResource" in the () mean for NSObject? What is that telling Xcode and the compiler about what is happening..? After that things look normal to me as they have various static and instance methods. I know that by doing this all user classes that inherit from NSObject now have all the extra methods for this project. My question is what is the parenthesis are doing after the NSObject. Is that referencing a header file, or is that letting the compiler know that this class is being over ridden. Thanks again and my apologies ahead of time if this is a dumb question but just trying to learn what I lack.

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  • Dynamically loading modules in Python (+ multi processing question)

    - by morpheous
    I am writing a Python package which reads the list of modules (along with ancillary data) from a configuration file. I then want to iterate through each of the dynamically loaded modules and invoke a do_work() function in it which will spawn a new process, so that the code runs ASYNCHRONOUSLY in a separate process. At the moment, I am importing the list of all known modules at the beginning of my main script - this is a nasty hack I feel, and is not very flexible, as well as being a maintenance pain. This is the function that spawns the processes. I will like to modify it to dynamically load the module when it is encountered. The key in the dictionary is the name of the module containing the code: def do_work(work_info): for (worker, dataset) in work_info.items(): #import the module defined by variable worker here... # [Edit] NOT using threads anymore, want to spawn processes asynchronously here... #t = threading.Thread(target=worker.do_work, args=[dataset]) # I'll NOT dameonize since spawned children need to clean up on shutdown # Since the threads will be holding resources #t.daemon = True #t.start() Question 1 When I call the function in my script (as written above), I get the following error: AttributeError: 'str' object has no attribute 'do_work' Which makes sense, since the dictionary key is a string (name of the module to be imported). When I add the statement: import worker before spawning the thread, I get the error: ImportError: No module named worker This is strange, since the variable name rather than the value it holds are being used - when I print the variable, I get the value (as I expect) whats going on? Question 2 As I mentioned in the comments section, I realize that the do_work() function written in the spawned children needs to cleanup after itself. My understanding is to write a clean_up function that is called when do_work() has completed successfully, or an unhandled exception is caught - is there anything more I need to do to ensure resources don't leak or leave the OS in an unstable state? Question 3 If I comment out the t.daemon flag statement, will the code stil run ASYNCHRONOUSLY?. The work carried out by the spawned children are pretty intensive, and I don't want to have to be waiting for one child to finish before spawning another child. BTW, I am aware that threading in Python is in reality, a kind of time sharing/slicing - thats ok Lastly is there a better (more Pythonic) way of doing what I'm trying to do? [Edit] After reading a little more about Pythons GIL and the threading (ahem - hack) in Python, I think its best to use separate processes instead (at least IIUC, the script can take advantage of multiple processes if they are available), so I will be spawning new processes instead of threads. I have some sample code for spawning processes, but it is a bit trivial (using lambad functions). I would like to know how to expand it, so that it can deal with running functions in a loaded module (like I am doing above). This is a snippet of what I have: def do_mp_bench(): q = mp.Queue() # Not only thread safe, but "process safe" p1 = mp.Process(target=lambda: q.put(sum(range(10000000)))) p2 = mp.Process(target=lambda: q.put(sum(range(10000000)))) p1.start() p2.start() r1 = q.get() r2 = q.get() return r1 + r2 How may I modify this to process a dictionary of modules and run a do_work() function in each loaded module in a new process?

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  • Variable Context Question

    - by Soo
    In the following code snippet, if I leave out the line of code that is surrounded by the /////'s, I get an error that reads: "Use of unassigned local variable CurrentDate". It seems a bit silly for me to just give CurrentDate an arbitrary value, is there a better way around this? DateTime CurrentDate; /////////////////////////// CurrentDate = DateTime.Now; /////////////////////////// if(1==1) { CurrentDate = DateTime.Now.AddDays(1); } if(CurrentDate == DateTime.Now) { ... }

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  • question about books

    - by davit-datuashvili
    i have question how good is this book? http://www.amazon.com/Concrete-Mathematics-Foundation-Computer-Science/dp/0201558025/ ? and can anybody advise good books about bit manipulations? for example how good is this book? http://www.amazon.com/Hackers-Delight-Henry-S-Warren/dp/0201914654/

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