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  • Are the atomic builtins provided by gcc actually translated into the example code, or is that just f

    - by Jared P
    So I was reading http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html, and came across this: type __sync_and_and_fetch (type *ptr, type value, ...) type __sync_xor_and_fetch (type *ptr, type value, ...) type __sync_nand_and_fetch (type *ptr, type value, ...) These builtins perform the operation suggested by the name, and return the new value. That is, { *ptr op= value; return *ptr; } { *ptr = ~*ptr & value; return *ptr; } // nand Is this code literal? or is it just to explain what gcc is doing atomically using c-like syntax? And if this is the direct translation, can someone explain how it is atomic?

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  • Ruby on Rails: Modules vs. Classes

    - by Jack
    I'm trying to add a function that will be accessible throughout all parts of my program. I want something like: def GlobalFunctions.my_function(x,y) puts x + y end to be accessible for all models. Specifically I am trying to use a function like this in my seeds.rb file but I am most likely going to be reusing the code and don't want any redundancy. Now I know I can make a simple class, but I could also make a module. What are some reasons to go in either direction? And once I've decided on which type to use, how do I make it accessible throughout the whole program? I have tried a module, but I keep getting " Expected app/[module file] to define [ModuleName]"

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  • Fast comparison of char arrays?

    - by StackedCrooked
    I'm currently working in a codebase where IPv4 addresses are represented as pointers to u_int8. The equality operator is implemented like this: bool Ipv4Address::operator==(const u_int8 * inAddress) const { return (*(u_int32*) this->myBytes == *(u_int32*) inAddress); } This is probably the fasted solution, but it causes the GCC compiler warning: ipv4address.cpp:65: warning: dereferencing type-punned pointer will break strict-aliasing rules How can I rewrite the comparison correctly without breaking strict-aliasing rules and without losing performance points? I have considered using either memcmp or this macro: #define IS_EQUAL(a, b) \ (a[0] == b[0] && a[1] == b[1] && a[2] == b[2] && a[3] == b[3]) I'm thinking that the macro is the fastest solution. What do you recommend?

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  • How do I return the indices of a multidimensional array element in C?

    - by Eddy
    Say I have a 2D array of random boolean ones and zeroes called 'lattice', and I have a 1D array called 'list' which lists the addresses of all the zeroes in the 2D array. This is how the arrays are defined: define n 100 bool lattice[n][n]; bool *list[n*n]; After filling the lattice with ones and zeroes, I store the addresses of the zeroes in list: for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { if(!lattice[i][j]) // if element = 0 { list[site_num] = &lattice[i][j]; // store address of zero site_num++; } } } How do I extract the x,y coordinates of each zero in the array? In other words, is there a way to return the indices of an array element through referring to its address?

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  • Python Class Variables Question

    - by zyq524
    I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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  • jQuery - Cycling through child elements

    - by Dan
    Hi, I have a series of select boxes within a table like so: <tr> <td><select></select></td> <td><select></select></td> <td><select></select></td> <td><select></select></td> </tr> With about 10 rows. I'm trying to reset all of the select boxes in the row to a default value, but having trouble with the syntax, can anyone help? This is what I have at the moment, but it dosen't seem to be working: $(row).children('td > select').each().val('0'); Any advice appreciated. Thanks.

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  • Cartesian Plane

    - by NuNu
    I'm trying to define a function in Haskell that takes an integer argument c and returns the list of all points on the cartesian plane of the form (x/c,y/c) where x and y are integers. x/c is between -2 and 1 and y/r is between -1 and 1 This is what I've gotten so far which I'm almost sure is right but I'm getting a parse error on input = when I run it particularly at this line: cart xs ys c = [(y/c,x/c) | x <- xs, y <- ys] plane :: Int -> [a] plane c = cart [-1*c .. 1*c] [-2*c .. 1*c] c cart xs ys c = [(y/c,x/c) | x <- xs, y <- ys] A sample output would be: plane 1 would generate: [(-2.0, -1.0), (-1.0, -1.0), ( 0.0, -1.0), ( 1.0, -1.0), (-2.0, 0.0), (-1.0, 0.0), ( 0.0, 0.0), ( 1.0, 0.0), (-2.0, 1.0), (-1.0, 1.0), ( 0.0, 1.0), ( 1.0, 1.0)] Anyone have any idea how I can fix this! Thanks

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  • Where should I set the DataContext - code behind or xaml?

    - by dovholuk
    (honestly I searched and read all the 'related questions' that seemed relevant - i do hope i didn't "miss" this question from elsewhere but here goes...) There are two different ways (at least) to set the DataContext. One can use XAML or one can use the code behind. What is the 'best practice' and why? I tend to favor setting it in XAML because it allows a designer to define collections on their own but I need 'ammunition' on why it's a best practice or why I'm crazy and the code behind is the bomb...

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  • How can I initialize a 2d array in Perl?

    - by Mark
    How do I initialize a 2d array in perl? I am trying the following code: 0 use strict; 10 my @frame_events = (((1) x 10), ((1) x 10)); 20 print "$frame_events[1][1]\n"; but it gives the following error: Can't use string ("1") as an ARRAY ref while "strict refs" in use at ./dyn_pf.pl line 20. This syntax only seems to initialize a 1d array as print "$frame_events[1]\n" works. Though perl doesn't give any error during the assignment.

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  • How exactly do you use json_decode to pass a javascript array to php?

    - by Adam
    This is how I got my php array to javascript echo 'var daysofweek = '.json_encode($daysofweek).';'; Now I am aware that json_decode can do the opposite, however the problem is I don't know the syntax to do so. I tried: <script> var array_days = new Array(); array_days[] = "psdfo"; array_days[] = "bsdf"; <?php $array_days = json_decode(?>array_days<?php);?> </script> yes im clueless. I forgot to mention that I want to send an array through post, having all my information regarding all the form values dynamically created by javascript. Otherwise, I wouldn't know which name="" to look for as it will be decided by the user. Unless someone else has an alternative solution...

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  • Haskell: foldl' accumulator parameter

    - by Clinton
    I've been asking a few questions about strictness, but I think I've missed the mark before. Hopefully this is more precise. Lets say we have: n = 1000000 f z = foldl' (\(x1, x2) y -> (x1 + y, y - x2)) z [1..n] Without changing f, what should I set z = ... So that f z does not overflow the stack? (i.e. runs in constant space regardless of the size of n) Its okay if the answer requires GHC extensions. My first thought is to define: g (a1, a2) = (!a1, !a2) and then z = g (0, 0) But I don't think g is valid Haskell.

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  • Expression parser library for Android.

    - by Malx
    What is the best way to evaluate simple conditional statements like: "a>b" ? "x-4<10+y & y>x" ? Expressions are loaded from external file. Variables are set in application. Syntax used is not essential. It may be "&" or "and" or any other supported with language/library. I need to take different action depending on result of evaluation - is it true or false. Could I use any parser already included with Andorid? Is there some way to use JS "eval" from browser component? Is it possible to use sqlite expressions to get true/false result without selecting anything? Those libraries are implemented in native code. Will it be faster and less battery expensive?

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  • Does the Internet make us less good programmers? [closed]

    - by stagas
    With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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  • Are C++ Templates just Macros in disguise?

    - by Roddy
    I've been programming in C++ for a few years, and I've used STL quite a bit and have created my own template classes a few times to see how it's done. Now I'm trying to integrate templates deeper into my OO design, and a nagging thought keeps coming back to me: They're just a macros, really... You could implement (rather UGLY) auto_ptrs using #defines, if you really wanted to. This way of thinking about templates helps me understand how my code will actually work, but I feel that I must be missing the point somehow. Macros are meant evil incarnate, yet "template metaprogramming" is all the rage. So, what ARE the real distinctions? and how can templates avoid the dangers that #define leads you into, like Inscrutable compiler errors in places where you don't expect them? Code bloat? Difficulty in tracing code? Setting Debugger Breakpoints?

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  • [Perl] Use a Module / Object which is defined in the same file

    - by Robert S. Barnes
    I need to define some modules and use them all in the same file. No, I can't change the requirement. I would like to do something like the following: { package FooObj; sub new { ... } sub add_data { ... } } { package BarObj; use FooObj; sub new { ... # BarObj "has a" FooObj my $self = ( myFoo => FooObj->new() ); ... } sub some_method { ... } } my $bar = BarObj->new(); However, this results in the message: Can't locate FooObj.pm in @INC ... BEGIN failed... How do I get this to work?

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  • Which HRESULT literal constant will fail the SUCCEEDED() macro?

    - by Hamish Grubijan
    Definition of SUCCEEDED(): #define SUCCEEDED(hr) (((HRESULT)(hr)) >= 0) Background: When an Ok button is clicked on a dialog, I need to return an HRESULT value hr such that SUCCEEDED(hr) is true. If Cancel button is clicked, I need to return a negative value. I could have used bools, but that would break the existing pattern (usually the hr values come from depths of system dlls). So, I know I can return S_OK on Ok, but what do I return on Cancel? I could just return (HRESULT)-1;, but there must be a better way - some HRESULT literal constant which has negative value and represents a generic failure. S_FALSE is not it, for it's value is defined as 1L. Please help me find the right constant.

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  • g++ no matching function call error

    - by gufftan
    I've got a compiler error but I can't figure out why. the .hpp: #ifndef _CGERADE_HPP #define _CGERADE_HPP #include "CVektor.hpp" #include <string> class CGerade { protected: CVektor o, rv; public: CGerade(CVektor n_o, CVektor n_rv); CVektor getPoint(float t); string toString(); }; the .cpp: #include "CGerade.hpp" CGerade::CGerade(CVektor n_o, CVektor n_rv) { o = n_o; rv = n_rv.getUnitVector(); } the error message: CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&) CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&)

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  • refresh a <ui:composition when j_security_check connection interrupted (http 408)

    - by José Osuna Barrios
    I have a "j_security_check connection interrupted (http code 408)" and proposed solution is <meta http-equiv="refresh" content="#{session.maxInactiveInterval}"/> by http://stackoverflow.com/a/2141274/1852036 but my page structure is a composition using a template.xhtml and a view.xhtml like a <ui:composition: my template.xhtml: <html ... <f:view ... <h:body ... <ui:insert name="content"> ... my view.xhtml to refresh when session.maxInactiveInterval <ui:composition ... <ui:define name="content"> ... may anyone help me to do this? I want to refresh this <ui:composition view, I can't use <meta http-equiv="refresh" content="#{session.maxInactiveInterval}"/> on template.xhtml because it's used by several views

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  • Is base method able to use derived base data members?

    - by iTayb
    Lets assume we have the following code: abstract class Base1 { protected int num; } class Der1:Base1 { protected Color color; protected string name; } class Der2:Base1 { protected DateTime dthen; } and so on. An array of base1 type exists and includes many objects created out of classes that are derived from base1. Is it possible to define the toString() method in the base class only? something like: public override string toString() { if (this is Der1) return "num = " + this.num + "color = " + this.color.toString() + " name = " this.name; if (this is Der2) return "num = " + this.num + "dthen = " + this.dthen.toString(); // and so on ... } Thank you very much :) P.S. This is not an homework question. I've just wondered about.

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  • Python: How to use code.InteractiveConsole?

    - by Rosarch
    I'm trying to use InteractiveConsole to create a new front-end for a Python interpreter. These code fragments are from me playing around with InteractiveConsole in IDLE: >>> ses = code.InteractiveConsole() >>> ses.runsource("def foo():") True >>> ses.runsource(" return 2") File "<input>", line 1 SyntaxError: 'return' outside function (<input>, line 1) False Why does it raise a syntax error? How else can I finish writing the function? Also, for something like this: >>> ses.runsource("x = 1") False >>> ses.runsource("x") 1 False How can I capture the 1 value from above? False is the return value, but 1 is written to some stream.

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  • Gaining Reference to the Dialog from Dialog content

    - by coffeeaddict
    Here's my scenario: I've got a div on Page A. When an event happens (whatever I define, a click, whatever), I do a div.Dialog, set its properties and open it The data inside is returned from an async .ajax call that grabs the data from a url and appends it to the div by calling div.html(data) inside the .ajax callback, so it's essentially loading a PageB by getting the data (content) and appending it to the div that's calling the dialog("open")...nothing special here I don't think. My question: In Page B, how do I reference the dialog so I can do some things to it? For instance in Page B's content that I received back from that .ajax call and added to the div via .html(data), there is a button and when clicked I need to close the dialog. Right now my buttons are not working because one of them closes out the dialog and the other should redirect to a new page but both do not work now because I have no reference to the dialog that it's in to manipulate it.

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  • How is push()ing and pop()ping defined?

    - by Helper Method
    I know how the push() and pop() methods in a typical implementation of a Queue/Linked List work but what I do want to know is what you actually define as a push or a pop? When can you name a method push()/pop()? What makes the insert()/add() method in a typical Tree implementation not a push()? My understanding is that push()ing means putting something to a position some special pointer is pointing to, and pop()ping an element means putting some object away some pointer is pointing to, but it doesn't seem to be clearly defined. Or does the naming matter at all?

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  • php multidimensional array if loop

    - by user1091558
    I have a multidimensional array like this array[value][1][1] Now i would like to implement if loop like this if ($value = array[value][1][1]) { echo "It works"; } Now it works if i assign the values like [1][1],[2][1]. Is it possible to compare the whole array. I mean if the array looks like array[value][1][1],array[value][2][1],..........,array[value][n][1] It works should be echoed. I tried like this. if ($value = array[value][][]) { echo "It works"; } But its not working. Can anyone give me the correct syntax?

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  • How do you pass self to class_eval in ruby?

    - by klochner
    I'm working on a metaprogramming task, where I'm trying to use a single method to define a polymorphic association in the calling class, while also defining the association in the target class. I need to pass in the name of the calling class to get the association right. Here's a snippet that should get the idea across: class SomeClass < ActiveRecord::Base has_many :join_models, :dependent=:destroy end class JoinModel < ActiveRecord::Base belongs_to :some_class belongs_to :entity, :polymorphic=true end module Foo module ClassMethods def acts_as_entity has_many :join_models, :as=:entity, :dependent=:destroy has_many :some_classes, :through=:join_models klass = self.name.tableize SomeClass.class_eval "has_many :#{klass}, :through=:join_models" end end end I'd like to eliminate the klass= line, but don't know how else to pass a reference to self from the calling class into class_eval. any suggestions?

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  • Re-use aliased field in SQL SELECT STATEMENT

    - by Bad Display Name
    Hi, the question is hard to define without giving an example, e.g. I'd like to achieve something like this : SELECT (CASE WHEN ...) AS FieldA, 20 + FieldA AS FieldB FROM Tbl Assuming that by "..." I've replaced a long and complex CASE statement, hence I don't want to repeat it when selecting FieldB and use the aliased FieldA instead. IS THIS EVEN POSSIBLE? What could be a workaround? Note, that this will return multiple rows , hence the DECLARE/SET outside the SELECT statement is no good in my case. PLEASE HELP. P.S. I am using SQL 2008

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