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• How to access global variable in a view in Ruby on Rails?

  - by ben

  I have a User model. I have a Session controller, in which I have a global user variable that is assigned as follows: $user = User.authenticate(params[:session][:email], params[:session][:password]) (I've made user global just to try to solve this problem, so if there's a better way please let me know!) I need to use the email of the logged in user as a parameter to send to Flex part of my website. At the moment I'm creating the link as follows: <%= link_to "secondpage", secondpage_path(:email => @session.$user.email) But I'm getting the following error: compile error /Users/benhartney/rails_projects/talk/app/views/layouts/_header.html.erb:12: syntax error, unexpected tGVAR ..._path(:email = @session.$user.email) ).to_s); @output_buffe... There's also a little arrow pointing at $user If I remove the $ from $user, I get this error: undefined method `user' for nil:NilClass If I remove the (:email => @session.user.email) part, everything works fine, so I think all of the code except for this is ok. Can anyone tell me what I'm doing wrong? Thanks for reading!

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• 2D Histogram in R: Converting from Count to Frequency within a Column

  - by Jac

  Would appreciate help with generating a 2D histogram of frequencies, where frequencies are calculated within a column. My main issue: converting from counts to column based frequency. Here's my starting code: # expected packages library(ggplot2) library(plyr) # generate example data corresponding to expected data input x_data = sample(101:200,10000, replace = TRUE) y_data = sample(1:100,10000, replace = TRUE) my_set = data.frame(x_data,y_data) # define x and y interval cut points x_seq = seq(100,200,10) y_seq = seq(0,100,10) # label samples as belonging within x and y intervals my_set$x_interval = cut(my_set$x_data,x_seq) my_set$y_interval = cut(my_set$y_data,y_seq) # determine count for each x,y block xy_df = ddply(my_set, c("x_interval","y_interval"),"nrow") # still need to convert for use with dplyr # convert from count to frequency based on formula: freq = count/sum(count in given x interval) ################ TRYING TO FIGURE OUT ################# # plot results fig_count <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = nrow)) # count fig_freq <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = freq)) # frequency I would appreciate any help in how to calculate the frequency within a column. Thanks! jac EDIT: I think the solution will require the following steps 1) Calculate and store overall counts for each x-interval factor 2) Divide the individual bin count by its corresponding x-interval factor count to obtain frequency. Not sure how to carry this out though. .

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• Magento config XML for adding a controller action to a core admin controller

  - by N. B.

  I'm trying to add a custom action to a core controller by extending it in a local module. Below I have the class definition which resides in magento1_3_2_2/app/code/local/MyCompany/MyModule/controllers/Catalog/ProductController.php class MyCompany_MyModule_Catalog_ProductController extends Mage_Adminhtml_Catalog_ProductController { public function massAttributeSetAction(){ ... } } Here is my config file at magento1_3_2_2/app/code/local/MyCompany/MyModule/etc/config.xml: ... <global> <rewrite> <mycompany_mymodule_catalog_product> <from><![CDATA[#^/catalog_product/massAttributeSet/#]]></from> <to>/mymodule/catalog_product/massAttributeSet/</to> </mycompany_mymodule_catalog_product> </rewrite> <admin> <routers> <MyCompany_MyModule> <use>admin</use> <args> <module>MyCompany_MyModule</module> <frontName>MyModule</frontName> </args> </MyCompany_MyModule> </routers> </admin> </global> ... However, https://example.com/index.php/admin/catalog_product/massAttributeSet/ simply yields a admin 404 page. I know that the module is active - other code is executing fine. I feel it's simply a problem with my xml syntax. Am I going about this the write way? I'm hesitant because I'm not actually rewriting a controller method... I'm adding one entirely. However it does make sense in that, the original admin url won't respond to that action name and it will need to be redirected. I'm using Magento 1.3.2.2 Thanks for any guidance.

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• C system calls open / read / write / close problem.

  - by Andrei Ciobanu

  Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR)) == -1){ write(2, "Error1\n", 7); } /* Writes hellow world to file */ if(write(filedes, FNAME, 10) != 10) write(2, "Error2\n", 7); /* Close file */ close(filedes); if((filedes = open(FNAME, O_RDONLY))==-1) write(2, "Error3\n", 7); /* Prints file contents on screen */ if((nbytes=read(filedes, buf, 128)) == -1) write(2, "Error4\n", 7); if(write(1, buf, nbytes) != nbytes) write(2, "Error5\n", 7); /* Close rile afte read */ close(filedes); return (0); } The first time i run the program, the output is: helloworld After that every time I to run the program, the output is: Error1 Error2 helloworld I don't understand why the text isn't appended, as I've specified the O_APPEND file. Is it because I've included O_CREAT ? It the file is already created, shouldn't O_CREAT be ignored ?

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• LINQ-SQL Updating Multiple Rows in a single transaction

  - by RPM1984

  Hi guys, I need help re-factoring this legacy LINQ-SQL code which is generating around 100 update statements. I'll keep playing around with the best solution, but would appreciate some ideas/past experience with this issue. Here's my code: List<Foo> foos; int userId = 123; using (DataClassesDataContext db = new FooDatabase()) { foos = (from f in db.FooBars where f.UserId = userId select f).ToList(); foreach (FooBar fooBar in foos) { fooBar.IsFoo = false; } db.SubmitChanges() } Essentially i want to update the IsFoo field to false for all records that have a particular UserId value. Whats happening is the .ToList() is firing off a query to get all the FooBars for a particular user, then for each Foo object, its executing an UPDATE statement updating the IsFoo property. Can the above code be re-factored to one single UPDATE statement? Ideally, the only SQL i want fired is the below: UPDATE FooBars SET IsFoo = FALSE WHERE UserId = 123 EDIT Ok so looks like it cant be done without using db.ExecuteCommand. Grr...! What i'll probably end up doing is creating another extension method for the DLINQ namespace. Still require some hardcoding (ie writing "WHERE" and "UPDATE"), but at least it hides most of the implementation details away from the actual LINQ query syntax.

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• How to solve generic algebra using solver/library programmatically? Matlab, Mathematica, Wolfram etc?

  - by DevDevDev

  I'm trying to build an algebra trainer for students. I want to construct a representative problem, define constraints and relationships on the parameters, and then generate a bunch of Latex formatted problems from the representation. As an example: A specific question might be: If y < 0 and (x+3)(y-5) = 0, what is x? Answer (x = -3) I would like to encode this as a Latex formatted problem like. If $y<0$ and $(x+constant_1)(y+constant_2)=0$ what is the value of x? Answer = -constant_1 And plug into my problem solver constant_1 > 0, constant_1 < 60, constant_1 = INTEGER constant_2 < 0, constant_2 > -60, constant_2 = INTEGER Then it will randomly construct me pairs of (constant_1, constant_2) that I can feed into my Latex generator. Obviously this is an extremely simple example with no real "solving" but hopefully it gets the point across. Things I'm looking for ideally in priority order * Solve algebra problems * Definition of relationships relatively straight forward * Rich support for latex formatting (not just writing encoded strings) Thanks!

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• install barnyard2 ubuntu 12.04

  - by Muhammad Ardiansyah

  I trying to install barnyard2 in ubuntu 12.04 32-bit I'm configure using syntax: ./configure --with-mysql-libraries=/usr/lib/x86_64-linux-gnu and when I trying to compile daq-1.1.1 using a makefile, I encountered the following errors: make[3]: Leaving directory /root/snortinstall/barnyard2/src' make[2]: Leaving directory/root/snortinstall/barnyard2/src' Making all in etc make[2]: Entering directory /root/snortinstall/barnyard2/etc' make[2]: Nothing to be done forall'. make[2]: Leaving directory /root/snortinstall/barnyard2/etc' Making all in doc make[2]: Entering directory/root/snortinstall/barnyard2/doc' make[2]: Nothing to be done for all'. make[2]: Leaving directory /root/snortinstall/barnyard2/doc' Making all in rpm make[2]: Entering directory /root/snortinstall/barnyard2/rpm' make[2]: Nothing to be done forall'. make[2]: Leaving directory /root/snortinstall/barnyard2/rpm' Making all in schemas make[2]: Entering directory/root/snortinstall/barnyard2/schemas' make[2]: Nothing to be done for all'. make[2]: Leaving directory /root/snortinstall/barnyard2/schemas' Making all in m4 make[2]: Entering directory /root/snortinstall/barnyard2/m4' make[2]: Nothing to be done forall'. make[2]: Leaving directory /root/snortinstall/barnyard2/m4' make[2]: Entering directory /root/snortinstall/barnyard2' make[2]: Nothing to be done for all-am'. make[2]: Leaving directory/root/snortinstall/barnyard2' make[1]: Leaving directory `/root/snortinstall/barnyard2'

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• Specify More "case" in switch parameters

  - by Sophie Mackeral

  I have the following code: $ErrorType = null; switch ($ErrNo){ case 256,1: $ErrorType = "Error"; break; case 512,2: $ErrorType = "Warning"; break; case 1024,8: $ErrorType = "Notice"; break; case 2048: $ErrorType = "Strict Warning"; break; case 8192: $ErrorType = "Depreciated"; break; } But the problem is, I'm going from the pre-defined constants for an error handling software solution.. I cannot specify more than one "case" for the dedicated error categories, example: switch ($ErrNo){ case 1: $ErrorType = "Error"; break; case 256: $ErrorType = "Error"; } That's a repeat of code.. Whereas with a solution like my first example, it would be beneficial as two integers fall under the same category.. Instead, i'm returned with the following: Parse error: syntax error, unexpected ',' in Action_Error.php on line 37

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• error: invalid type argument of '->' (have 'struct node')

  - by Roshan S.A

  Why cant i access the pointer "Cells" like an array ? i have allocated the appropriate memory why wont it act like an array here? it works like an array for a pointer of basic data types. #include<stdio.h> #include<stdlib.h> #include<ctype.h> #define MAX 10 struct node { int e; struct node *next; }; typedef struct node *List; typedef struct node *Position; struct Hashtable { int Tablesize; List Cells; }; typedef struct Hashtable *HashT; HashT Initialize(int SIZE,HashT H) { int i; H=(HashT)malloc(sizeof(struct Hashtable)); if(H!=NULL) { H->Tablesize=SIZE; printf("\n\t%d",H->Tablesize); H->Cells=(List)malloc(sizeof(struct node)* H->Tablesize); should it not act like an array from here on? if(H->Cells!=NULL) { for(i=0;i<H->Tablesize;i++) the following lines are the ones that throw the error { H->Cells[i]->next=NULL; H->Cells[i]->e=i; printf("\n %d",H->Cells[i]->e); } } } else printf("\nError!Out of Space"); } int main() { HashT H; H=Initialize(10,H); return 0; } The error I get is as in the title-error: invalid type argument of '->' (have 'struct node').

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• Ruby: how does constant-lookup work in instance_eval/class_eval?

  - by Alan O'Donnell

  I'm working my way through Pickaxe 1.9, and I'm a bit confused by constant-lookup in instance/class_eval blocks. I'm using 1.9.2. It seems that Ruby handles constant-lookup in *_eval blocks the same way it does method-lookup: look for a definition in receiver.singleton_class (plus mixins); then in receiver.singleton_class.superclass (plus mixins); then continue up the eigenchain until you get to #<Class:BasicObject>; whose superclass is Class; and then up the rest of the ancestor chain (including Object, which stores all the constants you define at the top-level), checking for mixins along the way Is this correct? The Pickaxe discussion is a bit terse. Some examples: class Foo CONST = 'Foo::CONST' class << self CONST = 'EigenFoo::CONST' end end Foo.instance_eval { CONST } # => 'EigenFoo::CONST' Foo.class_eval { CONST } # => 'EigenFoo::CONST', not 'Foo::CONST'! Foo.new.instance_eval { CONST } # => 'Foo::CONST' In the class_eval example, Foo-the-class isn't a stop along Foo-the-object's ancestor chain! And an example with mixins: module M CONST = "M::CONST" end module N CONST = "N::CONST" end class A include M extend N end A.instance_eval { CONST } # => "N::CONST", because N is mixed into A's eigenclass A.class_eval { CONST } # => "N::CONST", ditto A.new.instance_eval { CONST } # => "M::CONST", because A.new.class, A, mixes in M

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• How to store unlimited characters in Oracle 11g?

  - by vicky21

  We have a table in Oracle 11g with a varchar2 column. We use a proprietary programming language where this column is defined as string. Maximum we can store 2000 characters (4000 bytes) in this column. Now the requirement is such that the column needs to store more than 2000 characters (in fact unlimited characters). The DBAs don't like BLOB or LONG datatypes for maintenance reasons. The solution that I can think of is to remove this column from the original table and have a separate table for this column and then store each character in a row, in order to get unlimited characters. This tble will be joined with the original table for queries. Is there any better solution to this problem? UPDATE: The proprietary programming language allows to define variables of type string and blob, there is no option of CLOB. I understand the responses given, but I cannot take on the DBAs. I understand that deviating from BLOB or LONG will be developers' nightmare, but still cannot help it.

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• PHP gettext on Windows

  - by Axsuul

  There's some tutorials out there for gettext (w/ Poedit)... unfortunately, it's mostly for a UNIX environment. And even more unfortunate is that I am running my WAMP server on Windows XP (but I am developing for a UNIX environment) and none of the tutorials can get gettext working properly for me. From the man page (http://us3.php.net/manual/en/book.gettext.php), it appears that it's a different process on a Windows environment. I've tried out some of the solutions in the comments but I still can't get it to work! Please, I've spent many hours on this, hopefully someone can point me in the right direction to get this thing to work! (and I'm sure there are others out there who share my frustration). So far with my setup, I'm only getting output "Hello World!" whereas I should be getting the translated string. Here is my setup/code so far: <?php // test.php if (!defined('LC_MESSAGES')) { define('LC_MESSAGES', 6); } $locale = "deu_DEU"; // apparently the locales are different on a WINDOWS platform putenv("LC_ALL=$locale"); setlocale(LC_ALL, $locale); bindtextdomain("greetings", ".\locale"); textdomain("greetings"); echo _("Hello World"); ?> Folder structure root: C:\Program Files\WampServer 2\www test.php: C:\Program Files\WampServer 2\www\site .po: C:\Program Files\WampServer 2\www\site\locale\deu_DEU\LC_MESSAGES\greetings.po .mo: C:\Program Files\WampServer 2\www\site\locale\deu_DEU\LC_MESSAGES\greetings.mo Please advise! Thanks for your time :)

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• Which plugin framework to use for native C++/Win32

  - by Kerido

  Hi everybody. I have an extensible product that allows 3rd party developers to extend it. The aspects that can be extended are documented and interfaces are provided in the SDK. Currently, I'm using COM and I'm getting pretty comfortable with it. I especially like the ability to provide interface versioning in a unified manner. I consider it to be a requirement because you never know what you're gonna need in the future. Just to be precise, here's an example. Let's suppose I have an interface representing a particular feature: class IFeature { public: virtual void DoFeatureTask() = 0; }; Then after the interface is already documented (and someone may have used it in the plugin code) I'm realizing, I need more from this feature. Maybe, there is an option I need to provide. I just define the second version: class IFeature2 { public: virtual void DoFeatureTask(int theOption) = 0; }; I don't mean I intend to have lots of versions. But it just may happen. In COM, because every interface is associated with a GUID, I can query a preferred implementation, determine its presence, and, finally, fall back to a legacy one. But after glancing through C++/COM-related questions, I noticed many recommendations against COM. So maybe it's not the best choice and I'm just too old-school. Can you advise on an alternative?

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• gwtQuery's outerWidth(true) and IE8 not working without putting a delay

  - by Christopher

  I recently came across an odd behavior when trying to calculate the width (with margins) of an element using gwtQuery. The goal is to get the width (including padding, borders and margins) of a given element as a child of a certain parent. This parent may define specific CSS rules for some children so I clone it, add my element to this parent, call .outerWidth(true) to get the width and finally remove the clone from the parent. It works fine on Chrome, Firefox and IE 10, but randomly fails (outputs 0) on IE 8. However I noticed that if I put a "sleep" between the moment I add the element to the DOM and the moment I get the outer width, it always succeeds. I obviously don't want to keep that sleep. So my question is does anyone has any insights on how to work around this behavior or even a better way of achieving the same goal? Thank you! Here's a code snippet private Integer computeTabWidth(IsWidget tab) { GQuery $tab = $("<li></li>").append($(tab).clone()); $(containerPanel).append($tab); // IE 8 debug. sleep(100); Integer tabWidth = $tab.outerWidth(true); $tab.remove(); return tabWidth; } private void sleep(int i) { long time = new Date().getTime() + i; while (time > new Date().getTime()); }

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• Dealing with array of IntPtr

  - by Padu Merloti

  I think I'm close and I bet the solution is something stupid. I have a C++ native DLL where I define the following function: DllExport bool __stdcall Open(const char* filePath, int *numFrames, void** data); { //creates the list of arrays here... don't worry, lifetime is managed somewhere else //foreach item of the list: { BYTE* pByte = GetArray(i); //here's where my problem lives *(data + i * sizeofarray) = pByte; } *numFrames = total number of items in the list return true; } Basically, given a file path, this function creates a list of byte arrays (BYTE*) and should return a list of pointers via the data param. Each pointing to a different byte array. I want to pass an array of IntPtr from C# and be able to marshal each individual array in order. Here's the code I'm using: [DllImport("mydll.dll",EntryPoint = "Open")] private static extern bool MyOpen( string filePath, out int numFrames, out IntPtr[] ptr); internal static bool Open( string filePath, out int numFrames, out Bitmap[] images) { var ptrList = new IntPtr[512]; MyOpen(filePath, out numFrames, out ptrList); images = new Bitmap[numFrames]; var len = 100; //for sake of simplicity for (int i=0; i<numFrames;i++) { var buffer = new byte[len]; Marshal.Copy(ptrList[i], buffer, 0, len); images[i] = CreateBitmapFromBuffer(buffer, height, width); } return true; } Problem is in my C++ code. When I assign *(data + i * sizeofarray) = pByte; it corrupts the array of pointers... what am I doing wrong?

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• Common Lisp condition system for transfer of control

  - by Ken

  I'll admit right up front that the following is a pretty terrible description of what I want to do. Apologies in advance. Please ask questions to help me explain. :-) I've written ETLs in other languages that consist of individual operations that look something like: // in class CountOperation IEnumerable<Row> Execute(IEnumerable<Row> rows) { var count = 0; foreach (var row in rows) { row["record number"] = count++; yield return row; } } Then you string a number of these operations together, and call The Dispatcher, which is responsible for calling Operations and pushing data between them. I'm trying to do something similar in Common Lisp, and I want to use the same basic structure, i.e., each operation is defined like a normal function that inputs a list and outputs a list, but lazily. I can define-condition a condition (have-value) to use for yield-like behavior, and I can run it in a single loop, and it works great. I'm defining the operations the same way, looping through the inputs: (defun count-records (rows) (loop for count from 0 for row in rows do (signal 'have-value :value `(:count ,count @,row)))) The trouble is if I want to string together several operations, and run them. My first attempt at writing a dispatcher for these looks something like: (let ((next-op ...)) ;; pick an op from the set of all ops (loop (handler-bind ((have-value (...))) ;; records output from operation (setq next-op ...) ;; pick a new next-op (call next-op))) But restarts have only dynamic extent: each operation will have the same restart names. The restart isn't a Lisp object I can store, to store the state of a function: it's something you call by name (symbol) inside the handler block, not a continuation you can store for later use. Is it possible to do something like I want here? Or am I better off just making each operation function explicitly look at its input queue, and explicitly place values on the output queue?

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• How do I create a Status Icon / System Tray Icon with custom text and transparent background using P

  - by Raugturi

  Here is the code that I have so far to define the icon: icon_bg = gtk.gdk.pixbuf_new_from_file('gmail.png') w, h = icon_bg.get_width(), icon_bg.get_height() cmap = gtk.gdk.Colormap(gtk.gdk.visual_get_system(), False) drawable = gtk.gdk.Pixmap(None, w, h, 24) drawable.set_colormap = cmap gc = drawable.new_gc() drawable.draw_pixbuf(gc, icon_bg, 0, 0, 0, 0, w, h) drawn_icon = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, False, 8, w, h) drawn_icon.get_from_drawable(drawable, cmap, 0, 0, 0, 0, w, h) icon = gtk.status_icon_new_from_pixbuf(drawn_icon) This works to get the png into the icon, but falls short in two areas. First, transparency is not working. If I use a 22x22 png with transparent background and the image centered, I end up with sections of other active icons showing up inside of mine, like this: http://i237.photobucket.com/albums/ff311/Raugturi/22x22_image_with_transparency.png The icon it choose to steal from is somewhat random. Sometimes it's part of the dropbox icon, others the NetworkManager Applet. If I instead use this code: icon_bg = gtk.gdk.pixbuf_new_from_file('gmail.png') w, h = icon_bg.get_width(), icon_bg.get_height() cmap = gtk.gdk.Colormap(gtk.gdk.visual_get_system(), False) drawable = gtk.gdk.Pixmap(None, w, h, 24) drawable.set_colormap = cmap gc = drawable.new_gc() drawable.draw_pixbuf(gc, icon_bg, 0, 0, 0, 0, w, h) drawn_icon = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, False, 8, 22, 22) drawn_icon.get_from_drawable(drawable, cmap, 0, 0, 3, 6, w, h) icon = gtk.status_icon_new_from_pixbuf(drawn_icon) And an image that is only 16x11 with the transparent edges removed, what I end up with is this: Same URL but file is 16x11_image_positioned_in_middle.png So how do I end up with a transparent block like the 1st one that doesn't pull in stuff from other icons? As for the second problem, I need the ability to write on the image before converting it to the icon. I tried using draw_glyphs and it told me I should be using Pango layout/context instead. Unfortunately all the Pango tutorials I could find deal with actual windows, not the status icon. Is there a good tutorial out there for Pango that would apply to this issue (and also maybe have at least some explanation of how to tell it what font to use as all of them that I found seem to lack this and it won't write anything without it). Note: Sorry for the lack of actual images and only one working link, apparently this is a spam prevention feature due to my lack of reputation.

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• methods of metaclasses on class instances.

  - by Stefano Borini

  I was wondering what happens to methods declared on a metaclass. I expected that if you declare a method on a metaclass, it will end up being a classmethod, however, the behavior is different. Example >>> class A(object): ... @classmethod ... def foo(cls): ... print "foo" ... >>> a=A() >>> a.foo() foo >>> A.foo() foo However, if I try to define a metaclass and give it a method foo, it seems to work the same for the class, not for the instance. >>> class Meta(type): ... def foo(self): ... print "foo" ... >>> class A(object): ... __metaclass__=Meta ... def __init__(self): ... print "hello" ... >>> >>> a=A() hello >>> A.foo() foo >>> a.foo() Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'A' object has no attribute 'foo' What's going on here exactly ? edit: bumping the question

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• Extremely strange glitch in Chrome - parses contents of string!

  - by George Edison

  Okay - this is the dumbest glitch I have seen in a while: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <script type='text/javascript'> var data = "</script>"; </script> </head> <body> This should break! </body> </html> This causes syntax errors because the JavaScript parser is actually reading the contents of the string. How stupid! How can I put </script> in my code. Is there any way? Is there a valid reason for this behavior?

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• Division by zero: Undefined Behavior or Implementation Defined in C and/or C++ ?

  - by SiegeX

  Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. If we were to take the above paragraphs at face value, the answer is clearly Undefined Behavior for both languages. However, if we look further down in the C99 standard we see the following paragraph which appears to be contradictory(1): C99 7.12p4 - The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; Do the standards have some sort of golden rule where Undefined Behavior cannot be superseded by a (potentially) contradictory statement? Barring that, I don't think it's unreasonable to conclude that if your implementation defines the INFINITY macro, division by zero is defined to be such. However, if your implementation does not define such a macro, the behavior is Undefined. I'm curious what the consensus on this matter for each of the two languages. Would the answer change if we are talking about integer division int i = 1 / 0 versus floating point division float i = 1.0 / 0.0 ? Note (1) The C++03 standard talks about the library which includes the INFINITY macro.

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• OpenGL Nothing will Display

  - by m00st

  Why can't I get anything to display with this code? #include <iostream> #include "GL/glfw.h" #ifndef MAIN #define MAIN #include "GL/gl.h" #include "GL/glu.h" #endif using namespace std; void display(); int main() { int running = GL_TRUE; glfwInit(); if( !glfwOpenWindow( 640,480, 0,0,0,0,0,0, GLFW_WINDOW ) ) { glfwTerminate(); return 0; } while( running ) { //GL Code here display(); glfwSwapBuffers(); // Check if ESC key was pressed or window was closed running = !glfwGetKey( GLFW_KEY_ESC ) && glfwGetWindowParam( GLFW_OPENED ); } glfwTerminate(); return 0; } void display() { glClearColor(0, 0,0, 0.0f); glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); gluLookAt(0, 0, 5, 0.0, 0.0, 0.0, 0, 1, 0); glScalef(1.0f, 1.0f, 1.0f); glTranslatef(0, 0, -2); glBegin(GL_POLYGON); glColor3f(1.0, 0.2, 0.2); glVertex3f(0.25, 0.25, 0.0); glVertex3f(0.75, 0.25, 0.0); glVertex3f(0.75, 0.75, 0.0); glVertex3f(0.25, 0.75, 0.0); glEnd(); glFlush(); }

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• Template compilation error in Sun Studio 12

  - by Jagannath

  We are migrating to Sun Studio 12.1 and with the new compiler [ CC: Sun C++ 5.10 SunOS_sparc 2009/06/03 ]. I am getting compilation error while compiling a code that compiled fine with earlier version of Sun Compiler [ CC: Sun WorkShop 6 update 2 C++ 5.3 2001/05/15 ]. This is the compilation error I get. "Sample.cc": Error: Could not find a match for LoopThrough(int[2]) needed in main(). 1 Error(s) detected. * Error code 1. CODE: #include <iostream> #define PRINT_TRACE(STR) \ std::cout << __FILE__ << ":" << __LINE__ << ":" << STR << "\n"; template<size_t SZ> void LoopThrough(const int(&Item)[SZ]) { PRINT_TRACE("Specialized version"); for (size_t index = 0; index < SZ; ++index) { std::cout << Item[index] << "\n"; } } /* template<typename Type, size_t SZ> void LoopThrough(const Type(&Item)[SZ]) { PRINT_TRACE("Generic version"); } */ int main() { { int arr[] = { 1, 2 }; LoopThrough(arr); } } If I uncomment the code with Generic version, the code compiles fine and the generic version is called. I don't see this problem with MSVC 2010 with extensions disabled and the same case with ideone here. The specialized version of the function is called. Now the question is, is this a bug in Sun Compiler ? If yes, how could we file a bug report ?

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• Hide struct definition in static library.

  - by BobMcLaury

  Hi, I need to provide a C static library to the client and need to be able to make a struct definition unavailable. On top of that I need to be able to execute code before the main at library initialization using a global variable. Here's my code: private.h #ifndef PRIVATE_H #define PRIVATE_H typedef struct TEST test; #endif private.c (this should end up in a static library) #include "private.h" #include <stdio.h> struct TEST { TEST() { printf("Execute before main and have to be unavailable to the user.\n"); } int a; // Can be modified by the user int b; // Can be modified by the user int c; // Can be modified by the user } TEST; main.c test t; int main( void ) { t.a = 0; t.b = 0; t.c = 0; return 0; } Obviously this code doesn't work... but show what I need to do... Anybody knows how to make this work? I google quite a bit but can't find an answer, any help would be greatly appreciated. TIA!

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• Is there any benefit to my rather quirky character sizing convention?

  - by Paul Alan Taylor

  I love things that are a power of 2. I celebrated my 32nd birthday knowing it was the last time in 32 years I'd be able to claim that my age was a power of 2. I'm obsessed. It's like being some Z-list Batman villain, except without the colourful adventures and a face full of batarangs. I ensure that all my enum values are powers of 2, if only for future bitwise operations, and I'm reasonably assured that there is some purpose (even if latent) for doing it. Where I'm less sure, is in how I define the lengths of database fields. Again, I can't help it. Everything ends up being a power of 2. CREATE TABLE Person ( PersonID int IDENTITY PRIMARY KEY ,Firstname varchar(64) ,Surname varchar(128) ) Can any SQL super-boffins who know about the internals of how stuff is stored and retrieved tell me whether there is any benefit to my inexplicable obsession? Is it more efficient to size character fields this way? Can anyone pop in with an "actually, what you're doing works because ....."? I suspect I'm just getting crazier in my older age, but it'd be nice to know that there is some method to my madness.

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• Main Function Error C++

  - by Arjun Nayini

  I have this main function: #ifndef MAIN_CPP #define MAIN_CPP #include "dsets.h" using namespace std; int main(){ DisjointSets s; s.uptree.addelements(4); for(int i=0; i<s.uptree.size(); i++) cout <<uptree.at(i) << endl; return 0; } #endif And the following class: class DisjointSets { public: void addelements(int x); int find(int x); void setunion(int x, int y); private: vector<int> uptree; }; #endif My implementation is this: void DisjointSets::addelements(int x){ for(int i=0; i<x; i++) uptree.push_back(-1); } //Given an int this function finds the root associated with that node. int DisjointSets::find(int x){ //need path compression if(uptree.at(x) < 0) return x; else return find(uptree.at(x)); } //This function reorders the uptree in order to represent the union of two //subtrees void DisjointSets::setunion(int x, int y){ } Upon compiling main.cpp (g++ main.cpp) I'm getting these errors: dsets.h: In function \u2018int main()\u2019: dsets.h:25: error: \u2018std::vector DisjointSets::uptree\u2019 is private main.cpp:9: error: within this context main.cpp:9: error: \u2018class std::vector \u2019 has no member named \u2018addelements\u2019 dsets.h:25: error: \u2018std::vector DisjointSets::uptree\u2019 is private main.cpp:10: error: within this context main.cpp:11: error: \u2018uptree\u2019 was not declared in this scope I'm not sure exactly whats wrong. Any help would be appreciated.

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