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• Executing functions in series

  - by Latanmos

  Hi, First of all... Happy new year! Could you please explain to me, how does this work? I browsed throught Connect's (https://github.com/senchalabs/connect) source code, but I don't get it. I would like to write it by myself. app.get( '/', function(req, res, next) { // Set variable req.var = 'Happy new year!'; // Go to next function next(); }, function(req, res, next) { // Returns 'Happy new year!' console.log(req.var); // <- HOW IS THIS POSSIBLE? // (...) } ); Thanks in advance!

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• Why people define class, trait, object inside another object in Scala?

  - by Zwcat

  Ok, I'll explain why I ask this question. I begin to read Lift 2.2 source code these days. In Lift, I found that, define inner class and inner trait are very heavily used. object Menu has 2 inner traits and 4 inner classes. object Loc has 18 inner classes, 5 inner traits, 7 inner objects. There're tons of codes write like this. I wanna to know why the author write it like this. Is it because it's the author's personal taste or a powerful use of language feature?

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• Structure within union and bit field

  - by java

  #include <stdio.h> union u { struct st { int i : 4; int j : 4; int k : 4; int l; } st; int i; } u; int main() { u.i = 100; printf("%d, %d, %d", u.i, u.st.i, u.st.l); } I'm trying to figure out the output of program. The first outputs u.i = 100 but I can't understand the output for u.st.i and u.st.l. Please also explain bit fields.

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• Is an index required for columns in ON clause?

  - by newbie

  Do I have to create an index on columns referenced in Joins? E.g. SELECT * FROM left_table INNER JOIN right_table ON left_table.foo = right_table.bar WHERE ... Should I create indexes on left_table(foo), right_table(bar), or both? I noticed different results when I used EXPLAIN (Postgresql) with and without indexes and switching around the order of the comparison (right_table.bar = left_table.foo) I know for sure that indexes are used for the left of the WHERE clause but I am wondering whether I need indexes for columns listed in ON clauses.

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• Drawing lines between windows just like in Interface Builder

  - by Koning Baard

  I have two windows, each with a round NSView: ------------------ ------------ |X-+ Oscillator | |X-+ Mixer | |----------------| |----------| | | | | | O | | O | | | | | | | | | ------------------ ------------ Both windows are in a seperate NIB. I want to be able to draw a line between the two round NSViews at runtime, using drag'n'drop, just like connecting IBOutlets in Interface Builder: ------------------ ------------ |X-+ Oscillator | |X-+ Mixer | |----------------| |----------| | | | | | O-------+-----+-----O | | | | | | | | | ------------------ ------------ I also want to be able to determine to which NSViews the NSViews are connected using the drawn lines. I need this to connect Oscillators to Mixers. I also want to be able to remove the connections by dragging into empty space. Can anyone explain me how to do this? Thanks.

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• Does '[ab]+' equal '(a|b)+' in python re module?

  - by user1477871

  I think pat1 = '[ab]' and pat2 = 'a|b' have the same function in Python(python2.7, windows) 're' module as a regular expression pattern. But I am confused with '[ab]+' and '(a|b)+', do they have the same function, if not plz explain details. ''' Created on 2012-9-4 @author: melo ''' import re pat1 = '(a|b)+' pat2 = '[ab]+' text = '22ababbbaa33aaa44b55bb66abaa77babab88' m1 = re.search(pat1, text) m2 = re.search(pat2, text) print 'search with pat1:', m1.group() print 'search with pat2:', m2.group() m11 = re.split(pat1, text) m22 = re.split(pat2, text) print 'split with pat1:', m11 print 'split with pat2:', m22 m111 = re.findall(pat1, text) m222 = re.findall(pat2, text) print 'findall with pat1:', m111 print 'findall with pat2:', m222 output as below: search with pat1: ababbbaa search with pat2: ababbbaa split with pat1: ['22', 'a', '33', 'a', '44', 'b', '55', 'b', '66', 'a', '77', 'b', '88'] split with pat2: ['22', '33', '44', '55', '66', '77', '88'] findall with pat1: ['a', 'a', 'b', 'b', 'a', 'b'] findall with pat2: ['ababbbaa', 'aaa', 'b', 'bb', 'abaa', 'babab'] why are 'pat1' and 'pat2' different and what's their difference? what kind of strings can 'pat1' actually match?

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• Why javabeans framework create the IndexedPropertyDescriptor for the NON index method

  - by George Macus

  I'm not familiar with java beans framework, in the below scenario, I got the IndexedPropertyDescriptor for the method getFooWithX, could someone explain why? public class IntrospectorTest { public static void main(String[] args) throws IntrospectionException { BeanInfo info = Introspector.getBeanInfo(SubClass.class); PropertyDescriptor[] descriptors = info.getPropertyDescriptors(); for (int i = 0; i < descriptors.length; i++) { System.out.println(descriptors[i].getClass().getName() + ":" + descriptors[i].getName()); } } } abstract class BaseClass { public abstract Object getFoo(); } abstract class SubClass extends BaseClass { public Object getFooWithX(int x) { return null; } } and the result will be: java.beans.PropertyDescriptor:class java.beans.PropertyDescriptor:foo java.beans.IndexedPropertyDescriptor:fooWithX Why?

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• Problem with "not declared in this scope" error

  - by lego69

  I've got: error a1 was not declared in this scope Can somebody please explain why this code causes that? quiz.h #ifndef QUIZ_H_ #define QUIZ_H_ #include "quiz.cpp" class A { private: int player; public: A(int initPlayer); ~A(); void foo(); }; #endif /* QUIZ_H_ */ quiz.cpp #include "quiz.h" #include <iostream> using std::cout; using std::endl; A::A(int initPlayer = 0){ player = initPlayer; } A::~A(){ } void A::foo(){ cout << player; } main function #include "quiz.h" int main() { quiz(7); return 0; } quiz function #include "quiz.h" void quiz(int i) { A a1(i); a1.foo(); }

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• Which of these Array Initializations is better in Ruby?

  - by Bragaadeesh

  Hi, Which of these two forms of Array Initialization is better in Ruby? Method 1: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = Array.new(DAYS_IN_A_WEEK.size).map!{ Array.new(HOURS_IN_A_DAY.size) } DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day][hour] = 'something' end end Method 2: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = {} DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day] ||= {} @data[day][hour] = 'something' end end The difference between the first method and the second method is that the second one does not allocate memory initially. I feel the second one is a bit inferior when it comes to performance due to the numerous amount of Array copies that has to happen. However, it is not straight forward in Ruby to find what is happening. So, if someone can explain me which is better, it would be really great! Thanks

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• why are javascript functions like this

  - by Kajal

  I am a starter to javascript. I know to write JS userdefined functions. But recently I came across some thing that I can’t recognize. Can anyone explain to me what this is? (function( window, undefined ) { var jQuery = (function() { }); window.jQuery = window.$ = jQuery; })(window); What is the meaning of this? When I Google javascript functions I am getting only function foo(){ alert("This is an alert"); } I know to use these type of functions

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• Python and object/class attrs - what's going on?

  - by digitala

  Can someone explain why Python does the following? >>> class Foo(object): ... bar = [] ... >>> a = Foo() >>> b = Foo() >>> a.bar.append(1) >>> b.bar [1] >>> a.bar = 1 >>> a.bar 1 >>> b.bar [1] >>> a.bar = [] >>> a.bar [] >>> b.bar [1] >>> del a.bar >>> a.bar [1] It's rather confusing!

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• returning of the iterator in C++

  - by helloWorld

  can somebody explain I can I return list iterator? list<Account>::iterator Company::findAccount(int id){ for(list<Account>::iterator i = listOfAccounts.begin(); i != listOfAccounts.end(); ++i){ if(i->getID() == id){ return i; } } return 0; } and also is it good practice, to return list iterator? edited also can use this function in the statesments: if(findAccount(id)){ throw "hey"; return; }

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• What is this PHP Syntax: ($variation_id>0) ? $variation_id : $item_id;

  - by user1325258

  Is someone able to explain the meaing of the following statment, and the type of php it is reffering to so I can do further research: $foo = ($variation_id>0) ? $variation_id : $item_id; I have tried search but don't really know what i'm searching for. What I am trying to find out is the name and meaning of the following syntax ? / : and is ($variation_id>0) just a shorthand if statement ? -- I just stumbled upon conditional variables although a nice simple explanation would still be appreciated.

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• Solution to compiler warning for generic varargs

  - by TJR

  A puzzle from this blog. Similar to SO1445233. Given the following source listing, explain why the compiler is producing a warning at invocation to the list method and give a solution for removing the warning without resorting to @SuppressWarnings annotation. public class JavaLanguagePuzzle3 { public static void main(String[] args) { list("1", 2, new BigDecimal("3.5")); } private static <T> List<T> list(T... items) { return Arrays.asList(items); } } Warning: Type safety: A generic array of Object&Serializable&Comparable<?> is created for a varargs parameter

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• How to get the set events of a control?

  - by Jack

  It's possible via C# code get an list of methods/delegates that was set to Control? let me explain better.. For example. Assuming some definitions like this: foo.Click += (a, b) => { ... } //.. foo.Click += (A,B) => { ... } And a megic method: var baa = foo.GetEvents("Click"); Returns baa[0] points to (a, b) => { ... } baa[1] points to (A,B) => { ... } My scenery: I make and add dynamically event to some controls inside a loop. I want depending to a boolean value a event of control of index one,will removed by using control.Click -= baa[1] or something like this. I hope this is clear for your. Thanks in advance.

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• Is this a valid C statement ?

  - by Philando Gullible

  Lets say I write char c[99] = {'Stack Overflow'}; in C or C++ it does compiles fine but does this valid? By valid I meant not invoking any kind of undefined or unspecified behavior. Again if I write char c[99] = 'Stack Overflow'; gcc complains about multicharacter constant which is obvious but in the above when I am enclosing within curly brackets compiler is happy! why is it so ? I also notice that puts(c); after the first statement will output 'w' precisely the last character of a general string in-place of Stack Overflow. why so ? Could somebody explain this behavior may be separately.

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• What is this VB6 method doing?

  - by Craig

  We are converting a VB6 application to C# (4.0). and have come across a method in VB6 that we're battling to understand. Public Sub SaveToField(fldAttach As ADODB.Field) Dim bData() As Byte Dim nSize As Long nSize = Len(m_sEmail) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sEmail) fldAttach.AppendChunk bData End If nSize = Len(m_sName) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sName) fldAttach.AppendChunk bData End If bData = LngToByteArray(m_nContactID) fldAttach.AppendChunk bData End Sub It seems like it's doing some binary file copy type thing, but I'm not quite understanding. Could someone explain so that we can rewrite it?

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• base pointer to derived class

  - by Jay

  Suppose there are Base class and Derived class. Base *A = new Base; Here A is a pointer point to Base class, and new constructs one that A points to. I also saw Base *B = new Derived; How to explain this? B is a pointer to Base Class, and a Derived class constructed and pointed by B? If there is a function derived from Base class, say, Virtual void f(), and it's been overridden in Derived class, then B->f() will invoke which version of the function? version in Base class, or version that overridden in Derived Class. What if there is a new function void g()in Derived, is B->g() going to invoke this function properly? One more is, is int *a = new double; or int *a = new int; legal?

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• Performance problem on a query.

  - by yapiskan

  Hi, I have a performance problem on a query. First table is a Customer table which has millions records in it. Customer table has a column of email address and some other information about customer. Second table is a CommunicationInfo table which contains just Email addresses. And What I want in here is; how many times the email address in CommunicationInfo table repeats in Customers table. What could be the the most performer query. The basic query that I can explain this situation is; Select ci.Email, count(*) from Customer c left join CommunicationInfo ci on c.Email1 = ci.Email or c.Email2 = ci.Email Group by ci.Email But sure, it takes about 5, 6 minutes in execution. Thanks in Advance.

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• Is there an HTML code that can make my background picture transparent and my text non-transparent?

  - by user1831312

  Okay so I've been typing some HTML code for a technology class that I need to satisfy for my Education major. This is what i have for my background: body { background-image:url('islandbeach.jpg'); background-repeat:repeat; background-position:center; background-attachment:fixed; background-size:cover; } Now, I want to make my background transparent or faded so I can see the text and the other image that I have. The background is too colorful to be able to see the words without having to squint. Are there any HTML codes that can do this for me? I am not a pro at this stuff, I've just been following everything my professor has told me to do so please explain stuff in baby steps if you do have an answer. Thank you so so much!

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• what's the javascript "var _gaq = _gaq || []; " for ?

  - by parvas

  The Async Tracking in google analytics looks like this: var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-XXXXX-X']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); About The first line var _gaq = _gaq || []; I think it ensures that if _gaq is already defined we should use it otherwise we should an array. Can anybody explain what this is for ? Also, does it matter if _gaq gets renamed ? in other words does google analytics rely on a global object named _gaq ? Thanks Parvas

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• question about order in class

  - by helloWorld

  hello, can somebody please explain the order of private and public is important or no? for example: class Account{ public: Account(string firstName, string lastName, int id); void printAccount(); private: string strLastName; string strFirstName; }; will be the same as: class Account{ private: string strLastName; string strFirstName; public: Account(string firstName, string lastName, int id); void printAccount(); };

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• MySQL Multiple "AND" Query

  - by Mark J

  I have a table with 2 columns (see below). A member can have multiple responses to a question RESPONSES --------- member_id INT response_id INT SAMPLE DATA member_id -- response_id 1 -- 3 1 -- 5 2 -- 1 2 -- 5 2 -- 9 3 -- 1 3 -- 5 3 -- 6 What I need to do is query the table for member that meet ALL response criteria. For example I need to select all members that have a response_id of 1 AND 5. I am using the following query: SELECT DISTINCT member_id FROM responses WHERE response_id = 1 AND response_id = 5. I would expect to get back member_id's 2,3. However I am getting nothing returned. I used EXPLAIN and it shows there is an error in my where query. What am I doing wrong? Also, is there a function similar to IN where all the criteria must be met in order to return true? Thanks for your help.

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• [PHP] What exactly does it mean when $_FILES is empty?

  - by Mike

  I am working on a PHP upload script and when testing my error checks, I attempted to upload a 17MB TIFF file. When I do this the $_FILES array is empty. The script works fine for what I need it to do, which is to upload JPEG files. My solution is to test if $_FILES is empty or not before continuing with the upload script. Can anybody explain why $_FILES is empty when a TIFF is attempted to be uploaded? Is my solution, to check if $_FILES is empty or not, an okay one? Does this have something to do with settings in php.ini?

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• question about copy constructor

  - by lego69

  I have this class: class A { private: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); ~A(); void foo() const; }; and I have function which contains this row: A *pa1 = new A(a2); can somebody please explain what exactly is going on, when I call A(a2) compiler calls copy constructor or constructor, thanks in advance

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