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• Reuse C++ Header files

  - by Amrish

  Guys, I have a Visual C++ solution with 2 projects AlgorithmA & AlgorithmB and both share a common header file RunAlgo.h with the class declaration. Each project in the solution has its own unique implementation for the header file. I am trying to compile a DLL out of the common header file RunAlgo.h and add reference to this DLL in the projects AlgorithmA & AlgorithmB. I have then included separate RunAlgo.cpp definition file in both my projects. The problem is that I am getting linker errors while compiling the new DLL project which has only the header file. So, the question is Can a header file with only class declaration be compiled into a DLL (Similar to class library containing an Interface in C#)? For the above scenario, is there a better approach to reuse the common Header file among projects? Should the above method work (re-check my code?)

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• Class works without declaring variables?

  - by Maxim Droy

  I'm learned php as functional and procedure language. Right now try to start learn objective-oriented and got an important question. I have code: class car { function set_car($model) { $this->model = $model; } function check_model() { if($this->model == "Mercedes") echo "Good car"; } } $mycar = new car; $mycar->set_car("Mercedes"); echo $mycar->check_model(); Why it does work without declaration of $model? var $model; in the begin? Because in php works "auto-declaration" for any variables? I'm stuck

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• How to use Mysql variables with Hibernate ?

  - by Jerome C.

  Hello, I need to use a native sql query in Hibernate with use of variable. But hibernate throws an error saying: Space is not allowed after parameter prefix So there is a conflict with the := mysql variable assignment and hibernate variable assignment. Here is my sql query: SET @rank:=0; UPDATE Rank SET rank_Level=@rank:=@rank+1 ORDER BY Level; I can't use a stored procedure because my sql query is dynamically generated ('Level' can be 'int' or 'force'...) How can I do this ? thanks

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• Best way to handle enable/disable of UIButtons on iPhone

  - by Anonymous

  I have an increase button and a decrease button, both of which affect a variable. The variable has a minimum and the decrease button will be disabled once that minimum is reached. Likewise for the maximum value of the variable. In my controller, I have two IBActions for both the increase and decrease actions, and two IBOutlets, in order to disable the buttons accordingly. At the bottom of my KVO statement to handle the value change, I have: increaseButton.enabled = value != MAX; decreaseButton.enabled = value != MIN; While this code is functional, I can't help but feel that feel this is a naive approach to the problem, especially since this requires 4 connections. Is there a better solution to this, one that uses fewer connections?

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• Global variables in hadoop.

  - by Deepak Konidena

  Hi, My program follows a iterative map/reduce approach. And it needs to stop if certain conditions are met. Is there anyway i can set a global variable that can be distributed across all map/reduce tasks and check if the global variable reaches the condition for completion. Something like this. While(Condition != true){ Configuration conf = getConf(); Job job = new Job(conf, "Dijkstra Graph Search"); job.setJarByClass(GraphSearch.class); job.setMapperClass(DijkstraMap.class); job.setReducerClass(DijkstraReduce.class); job.setOutputKeyClass(IntWritable.class); job.setOutputValueClass(Text.class); } Where condition is a global variable that is modified during/after each map/reduce execution.

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• Why is volatile not considered useful in multithreaded C or C++ programming?

  - by Michael E

  As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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• Problem when trying to define Show for my Point3D type in Haskell

  - by devoured elysium

  I am trying to define Show for my Point3D type: type Point3D = (Integer, Integer, Integer) instance Show Point3D where show (x,y,z) = "<" ++ (show x) ++ "," ++ (show y) ++ "," ++ (show z) ++ ">" yet I must be missing something in the sintax, as I am always getting an error: Illegal instance declaration for `Show Point3D' (All instance types must be of the form (T t1 ... tn) where T is not a synonym. Use -XTypeSynonymInstances if you want to disable this.) In the instance declaration for `Show Point3D' What am I doing wrong?

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• I am having trouble with my first project in ruby on rails

  - by Sebastian

  Here's my index action in the books controller: http://pastebin.com/XdtGRQKV Here's the view for the action i just mentioned: http://pastebin.com/nQFy400m Here's the result without being logged in: http://i.imgur.com/rQoiw.jpg Here's the result when i'm logged in with the user 'admin': http://i.imgur.com/E1CUr.jpg So the problem is that, in the view, before line 25 the 'user' variable seems to be empty ( or not loaded), and after line 25 the variable 'user' has the expected values. I have tried initializing a variable in the index method of the books controller but get exactly the same results. Thanks in advance! BTW had to make the links text because of stackoverflow limit.

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• namespace in c++

  - by Codenotguru

  what is the use of using declaration type of namespacing over using directive type of namespacing??when to use each one of them?

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• Safe to cast pointer to a forward-declared class to its true base class in C++?

  - by Matt DiMeo

  In one header file I have: #include "BaseClass.h" // a forward declaration of DerivedClass, which extends class BaseClass. class DerivedClass ; class Foo { DerivedClass *derived ; void someMethod() { // this is the cast I'm worried about. ((BaseClass*)derived)->baseClassMethod() ; } }; Now, DerivedClass is (in its own header file) derived from BaseClass, but the compiler doesn't know that at the time it's reading the definition above for class Foo. However, Foo refers to DerivedClass pointers and DerivedClass refers to Foo pointers, so they can't both know each other's declaration. First question is whether it's safe (according to C++ spec, not in any given compiler) to cast a derived class pointer to its base class pointer type in the absence of a full definition of the derived class. Second question is whether there's a better approach. I'm aware I could move someMethod()'s body out of the class definition, but in this case it's important that it be inlined (part of an actual, measured hotspot - I'm not guessing).

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• Does declaring many identical anonymous classes waste memory in java?

  - by depsypher

  I recently ran across the following snippet in an existing codebase I'm working on and added the comment you see there. I know this particular piece of code can be rewritten to be cleaner, but I just wonder if my analysis is correct. Will java create a new class declaration and store it in perm gen space for every call of this method, or will it know to reuse an existing declaration? protected List<Object> extractParams(HibernateObjectColumn column, String stringVal) { // FIXME: could be creating a *lot* of anonymous classes which wastes perm-gen space right? return new ArrayList<Object>() { { add(""); } }; }

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• Setting new class variables inside a module

  - by Sean McCleary

  I have a plugin I have been working on that adds publishing to ActiveRecord classes. I extend my classes with my publisher like so: class Note < ActiveRecord::Base # ... publishable :related_attributes => [:taggings] end My publisher is structured like: module Publisher def self.included(base) base.send(:extend, ClassMethods) @@publishing_options = [] # does not seem to be available end module ClassMethods def publishable options={} include InstanceMethods @@publishing_options = options # does not work as class_variable_set is a private method # self.class_variable_set(:@@publishing_options, options) # results in: uninitialized class variable @@publishing_options in Publisher::ClassMethods puts "@@publishing_options: #{@@publishing_options.inspect}" # ... end # ... end module InstanceMethods # results in: uninitialized class variable @@publishing_options in Publisher::InstanceMethods def related_attributes @@publishing_options[:related_attributes] end # ... end end Any ideas on how to pass options to publishable and have them available as a class variable?

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• Writing Strings to files in python

  - by Leif Andersen

  I'm getting the following error when trying to write a string to a file in pythion: Traceback (most recent call last): File "export_off.py", line 264, in execute save_off(self.properties.path, context) File "export_off.py", line 244, in save_off primary.write(file) File "export_off.py", line 181, in write variable.write(file) File "export_off.py", line 118, in write file.write(self.value) TypeError: must be bytes or buffer, not str I basically have a string class, which contains a string: class _off_str(object): __slots__ = 'value' def __init__(self, val=""): self.value=val def get_size(self): return SZ_SHORT def write(self,file): file.write(self.value) def __str__(self): return str(self.value) Furthermore, I'm calling that class like this: def write(self, file): for variable in self.variables: variable.write(file) I have no idea what is going on. I've seen other python programs writing strings to files, so why can't this one? Thank you very much for your help.

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• Updating variables in XSL

  - by Stroboskop

  Is there any way in XSL to update a global variable? I want to check what elements i already transformed and act accordingly. That would require me to somehow add the names of the elements to some sort of list and update it each time a new element is transformed. But since xsl:variable isn't "variable" in the sense one would expect, i have no way of adding anything to it once it has been defined. I have multiple included data files, so using xsl functions that only know the current set of nodes will not help.

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• Function in xcode

  - by Joy

  I have a function which have two global variable 1.temp-a nsmutable array 2.j-a int type variable. But i cant access any global variable inside this function. I'm giving the code sample. void print( NSArray *array) { NSEnumerator *enumerator = [array objectEnumerator]; id obj; while ( nil!=(obj = [enumerator nextObject]) ) { NSString *tem=[[obj description] cString]; [temp insertObject:tem atIndex:j]; j=j+1; printf( "%s\n", [[obj description] cString]); } } Looking forward to your response. Thanks in advance..

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• Testing for the presence of a character in an string in C

  - by Prab

  What's wrong with this? #include <stdio.h> void main(){ char *s="some text"; printf("%d",is_in(s,'t')); } int is_in(char *s, char c){ while(*s){ if(*s==c) return 1; s++; } return 0; } I get the following compile time error with GCC: test.c:9: error: conflicting types for ‘is_in’ test.c:9: note: an argument type that has a default promotion can’t match an empty parameter name list declaration test.c:5: note: previous implicit declaration of ‘is_in’ was here

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• About first-,second- and third-class value

  - by forest58

  First-class value can be passed as an argument returned from a subroutine assigned into a variable. Second-class value just can be passed as an argument. Third-class value even can't be passed as an argument. Why should these things defined like that? As I understand, "can be passed as an argument" means it can be pushed into the runtime stack;"can be assigned into a variable" means it can be moved into a different location of the memory; "can be returned from a subroutine" almost has the same meaning of "can be assigned into a variable" since the returned value always be put into a known address, so first class value is totally "movable" or "dynamic",second class value is half "movable" , and third class value is just "static", such as labels in C/C++ which just can be addressed by goto statement, and you can't do nothing with that address except "goto" .Does My understanding make any sense? or what do these three kinds of values mean exactly?

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• How can I use jQuery for messing with a particular div, but not in the current document - in a varia

  - by bisaram

  How can I use jQuery for messing with a particular div, but not in the current document - in a variable, that contains HTML? The point is that I want to show a preview of a page (a piece of it's content) in a modal window, when the link to this page is clicked. Well, onClick I load this whole HTML into a variable via JSON and then... how would I find a particular div I need in it? It's gonna be almost impossible to parse it with PHP before converting it into JSON and giving back to jQuery processor because of a deep hierarchy. Basically, is it even possible to do smth like $( 'div#some-id' ).blabla(); not for the current document, but for the document, stored in a variable? Thx everyone in advance.

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• Can a programming language without arrays be turing-complete?

  - by Ring

  My question is simple: There are no arrays possible. That means you can address variables only "statically" by directly using their unique name. (This already throws out the default array syntax variable[ index ] and variable variables) "Emulated arrays" are counted as arrays and excluded too. Examples: You could basically simulate arrays using strings (quite easily actually) or use variable variables as in PHP. Can such a language be turing-complete? Brainf*ck for example has arrays, in fact it is one big array, isn't it?

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• Guidance for Php for a beginner

  - by luckyluke

  I've just started to learn PHP. I found the $_POST variable is not working and posted the same at the below link $_POST[] not working in php and as per the advise i installed XAMPP. But still the proble of $_POST variable is not solved. Now i've a doubt whether i need to configure any global variable to make $_POST work. I'm totally lost on this and dont know how to proceed. Any help on this is verryy much appreciated. Thanks.

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• How can I create an enum using numbers?

  - by Jordan S

  Is it possible to make an enum using just numbers in C#? In my program I have a variable, Gain, that can only be set to 1, 2, 4, and 8. I am using a propertygrid control to display and set this value. If I were to create an enum like this... private enum GainValues {One, Two, Four, Eight} and I made my gain variable of type GainValues then the drop-down list in the propertygrid would only show the available values for the gain variable. The problem is I want the gain values to read numerically an not as words. But I can not create an enum like this: private enum GainValues {1,2,4,8} So is there another way of doing this? Perhaps creating a custom type?

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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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• GWT - Retrieve size of a widget that is not displayed

  - by Garagos

  I need to set the size of an absolutePanel regarding to its child size, but the getOffset* methods return 0 because (i think) the child as not been displayed yet. A Quick example: AbsolutePanel aPanel = new AbsolutePanel(); HTML text = new HTML(/*variable lenght text*/); int xPosition = 20; // actually variable aPanel.add(text, xPosition, 0); aPanel.setSize(xPosition + text .getOffsetWidth() + "px", "50px"); // 20px 50px I could also solve my problem by using the AbsolutePanel size to set the child position and size: AbsolutePanel aPanel = new AbsolutePanel(); aPanel.setSize("100%", "50px"); HTML text = new HTML(/*variable lenght text*/); int xPosition = aPanel.getOffsetWidth() / 3; // Once again, getOffsetWidth() returns 0; aPanel.add(text, xPosition, 0); In both case, i have to find a way to either: retrieve the size of a widget that has not been displayed be notified when a widget is displayed

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• Deselecting an element in jQuery

  - by Michael Itzoe

  I have a collection of span elements. In the code I have a global variable that represents the "selected" object. Using the click event when a span is clicked I reset the object's class, reset the global variable, then set the object to the variable and change its class (to make it "highlighted"). This effectively toggles selection when clicking an object. var currentItem = null; $( ".item" ).click( function() { if( $( this ).hasClass( "selected" ) ) { $( this ).removeClass( "selected" ) currentItem = null; } else { if( $( ".item" ).hasClass( "selected" ) ){ $( ".item" ).removeClass( "selected" ) } $( this ).addClass( "selected" ); currentItem = $( this ); } } ); What I'd like to be able to do is unselect when clicking on an empty area of the page. I tried creating a click event on the body object, but that overrode the span click event so nothing was selected. I'm a complete jQuery noob and not sure where to go with this.

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• Double # showing 0 on android

  - by Dave

  I'm embarrassed to ask this question, but after 45 minutes of not finding a solution I will resort to public humiliation. I have a number that is being divided by another number and I'm storing that number in a double variable. The numbers are randomly generated, but debugging the app shows that both numbers are in fact being generated. Lets just say the numbers are 476 & 733. I then take the numbers and divide them to get the percentage 476/733 = .64 I then print out the variable and it's always set to 0. I've tried using DecimalFormat and NumberFormat. No matter what I try though it always says the variable is 0. I know there is something simple that I'm missing, I just can't find it =/.

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