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• In SQL, we can use "Union" to merge two tables. What are different ways to do "Intersection"?

  - by Jian Lin

  In SQL, there is an operator to "Union" two tables. In an interview, I was told that, say one table has just 1 field with 1, 2, 7, 8 in it, and another table also has just 1 field with 2, and 7 in it, how do I get the intersection. I was stunned at first, because I never saw it that way. Later on, I found that it is actually a "Join" (inner join), which is just select * from t1, t2 where t1.number = t2.number (although the name "join" feels more like "union" rather than "intersect") another solution seems to be select * from t1 INTERSECT select * from t2 but it is not supported in MySQL. Are there different ways to get the intersection besides these two methods?

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• Is this call to a function object inlined?

  - by dehmann

  In the following code, Foo::add calls a function via a function object: struct Plus { inline int operator()(int x, int y) const { return x + y; } }; template<class Fct> struct Foo { Fct fct; Foo(Fct f) : fct(f) {} inline int add(int x, int y) { return fct(x,y); // same efficiency adding directly? } }; Is this the same efficiency as calling x+y directly in Foo::add? In other words, does the compiler typically directly replace fct(x,y) with the actual call, inlining the code, when compiling with optimizations enabled?

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• Continuing JavaScript "classes" - enums within

  - by espais

  From a previous question, I have the following: So I have implemented a resource class, now I'd like to continue extending it and add all my constants and enums (or as far as JS will allow...). This is what I currently have: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png") }; And this is what I would like to continue to extend it to: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png"), // enums directions : {up:0, right:1, down:2, left:3}, speeds : {slow: 1, medium: 3, fast: 5} }; ... function enemies() { this.dir = resources.directions.down; // initialize to down } When I attempt to access resources.directions.up, my JS script goes down in a flaming pile of burning code. Are enums allowed in this context, and if not, how can I properly insert them to be used outside of a normal function? I have also tried defining them as global to a similar effect. edits: fixed the comma...that was just an error in transcribing it. When I run it in Firefox and watch the console, I get an error that says resources is undefined. The resources 'class' is defined at the top of my script, and function enemies() directly follows...so from what I understand it should still be in scope...

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• Consing lists with user-defined type in Haskell

  - by user1319603

  I have this type I defined myself: data Item = Book String String String Int -- Title, Author, Year, Qty | Movie String String String Int -- Title, Director, Year, Qty | CD String String String Int deriving Show -- Title, Artist, Year, Qty I've created an empty list all_Items = [] With the following function I am trying to insert a new book of type Item (Book) into the all_Items addBook all_Items = do putStrLn "Enter the title of the book" tit <- getLine putStrLn "Enter the author of the book" aut <- getLine putStrLn "Enter the year this book was published" yr <- getLine putStrLn "Enter quantity of copies for this item in the inventory" qty <- getLine Book tit aut yr (read qty::Int):all_Items return(all_Items) I however am receiving this error: Couldn't match expected type `IO a0' with actual type `[a1]' The error points to the line where I am using the consing operator to add the new book to the list. I can gather that it is a type error but I can't figure out what it is that I am doing wrong and how to fix it. Thanks in Advance!

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• visual studio intellisense error

  - by rakkarage

  template <typename T> class Test { friend Test<T> & operator * (T lhs, const Test<T> & rhs) { Test<T> r(rhs); // return r *= lhs; } } 4 IntelliSense: identifier "T" is undefined why is T defined on line 3 but not line 4? i mean i guess its not a real error just an intellisense error... it works anyway but is there something wrong? can i fix it? or remove the red squiggles somehow? thanks i am using visual studio 2010... i wonder if this happens in other versions as well?

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• C# : Number Conversion Problem

  - by Sayem Ahmed

  Today I faced a strange problem in C#. I have an ASP.NET page where user can enter certain price, quantity etc. I get the price value, convert it to double, then multiply it with 100 and then typecast it to an integer. When the price is "33.30", after converting it to double it remains 33.3 (obviously...), but after multiplying it with 100, it becomes 3329.9999999999995, and when I cast it to integer by applying simple cast operator "(int) (price * 100) ", it becomes 3329. Right now I have no idea why this is happening. So I thought may be you guys can help :) .

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• When does ref($variable) return 'IO'?

  - by Zaid

  Here's the relevant excerpt from the documentation of the ref function: The value returned depends on the type of thing the reference is a reference to. Builtin types include: SCALAR ARRAY HASH CODE REF GLOB LVALUE FORMAT IO VSTRING Regexp Based on this, I imagined that calling ref on a filehandle would return 'IO'. Surprisingly, it doesn't: use strict; use warnings; open my $fileHandle, '<', 'aValidFile'; close $fileHandle; print ref $fileHandle; # prints 'GLOB', not 'IO' perlref tries to explain why: It isn't possible to create a true reference to an IO handle (filehandle or dirhandle) using the backslash operator. The most you can get is a reference to a typeglob, which is actually a complete symbol table entry [...] However, you can still use type globs and globrefs as though they were IO handles. In what circumstances would ref return 'IO' then?

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• SQL vs MySQL: Rules about aggregate operations and GROUP BY

  - by Phazyck

  In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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• PIC C - Sending 200 values over USB, but it only sends 25 or so of them...

  - by Adam

  I have a PIC18F4455 microcontroller which I am trying to use to send 200 values over USB. Basically I am using a for loop and a printf statement to print the values to the usb output stream. However, when the code executes I see in my serial port monitor that it is only sending the first 25 or so values, then stopping. My PIC C code is below. It will send out the 25th or so value (and the comma), but not send anything after and not send a newline character. I'm trying to get it to send all the values, then a newline character at the end. I am sending them all as characters because I can convert them on the PC end of it. //print #3 for (i = 0; i <= 199; i++){if (data[i]=='\0' || data[i]=='\n'){data[i]++;}} for (i = 0; i < 199; i++){printf(usb_cdc_putc, "%c,", data[i]);} printf(usb_cdc_putc, "%c\n", data[199]);

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• PIC C - Sending 200 values over USB, but it only sends 25 of them...

  - by Adam

  I have a PIC18F4455 microcontroller which I am trying to use to send 200 values over USB. Basically I am using a for loop and a printf statement to print the values to the usb output stream. However, when the code executes I see in my serial port monitor that it is only sending the first 25 values, then stopping. My PIC C code is below. It will send out the 25th value (and the comma), but not send anything after and not send a newline character. I'm trying to get it to send all the values, then a newline character at the end. I am sending them all as characters because I can convert them on the PC end of it. //print #3 for (i = 0; i <= 199; i++){if (data[i]=='\0' || data[i]=='\n'){data[i]++;}} for (i = 0; i < 199; i++){printf(usb_cdc_putc, "%c,", data[i]);} printf(usb_cdc_putc, "%c\n", data[199]);

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• Is there alternative way to write this query?

  - by Kugel

  I have tables A, B, C, where A represents items which can have zero or more sub-items stored in C. B table only has 2 foreign keys to connect A and C. I have this sql query: select * from A where not exists (select * from B natural join C where B.id = A.id and C.value > 10); Which says: "Give me every item from table A where all sub-items have value less than 10. Is there a way to optimize this? And is there a way to write this not using exists operator?

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• drupal themes: .info file: how do I add more than 1 css file / js file to my theme?

  - by egarcia

  I'm creating a new Drupal theme. Until now, I only needed to include a single css file and a single js file. So my theme.info file had something like this: stylesheets[all][] = css/style.css scripts[] = js/script.js Now I must include jquery and jquery-ui in order to use a calendar date. These come with 2 new javascript files, and 1 additonal css file that I must add to the site. The calendar input form is going to be used in all pages (on a side block) so it is ok for me to load the extra css/javascript on all pages. I think the easiest thing would be to reference them on the .info file itself. At first I tried to just put them there with separate spaces: stylesheets[all][] = css/style.css css/ui-lightness/jquery-ui-1.8.1.custom.css scripts[] = js/jquery-1.4.2.min.js js/jquery-ui-1.8.1.custom.min.js js/reservations.js I emptied drupal's cache and... none of them loaded. I then tried separating each file with a comma, and flushing the cache again. Same result. I've browsed some drupal pages, but could not find how to add several javascript/css files on one theme (they always seem to add just 1 of each). So, how do I include several css/javascript files on the .info file?

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• Problem of using cin twice.

  - by gc

  Here is the code: string str; cinstr; cout<<"first input:"<<str<<endl; getline(cin, str); cout<<"line input:"<<str<<endl; The result is that getline never pauses for user input, therefore the second output is always empty. After spending some time on it, I realized after the first call "cinstr", it seems '\n' is still stored in cin (using cin.peek() to check), which ends getline immediately. The solution will be adding one more line between the first usage and the second one: cin.ignore(numeric_limits::max(), '\n'); However, I still don't understand, why is '\n' left there after the first call? What does istream& operator really do?

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• How to write a good PHP database insert using an associative array

  - by Tom

  In PHP, I want to insert into a database using data contained in a associative array of field/value pairs. Example: $_fields = array('field1'=>'value1','field2'=>'value2','field3'=>'value3'); The resulting SQL insert should look as follows: INSERT INTO table (field1,field2,field3) VALUES ('value1','value2','value3'); I have come up with the following PHP one-liner: mysql_query("INSERT INTO table (".implode(',',array_keys($_fields)).") VALUES (".implode(',',array_values($_fields)).")"); It separates the keys and values of the the associative array and implodes to generate a comma-separated string . The problem is that it does not escape or quote the values that were inserted into the database. To illustrate the danger, Imagine if $_fields contained the following: $_fields = array('field1'=>"naustyvalue); drop table members; --"); The following SQL would be generated: INSERT INTO table (field1) VALUES (naustyvalue); drop table members; --; Luckily, multiple queries are not supported, nevertheless quoting and escaping are essential to prevent SQL injection vulnerabilities. How do you write your PHP Mysql Inserts? Note: PDO or mysqli prepared queries aren't currently an option for me because the codebase already uses mysql extensively - a change is planned but it'd take alot of resources to convert?

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• formatting an array of mobile numbers

  - by Kyle Hudson

  Hi, I am creating a SMS app the following code is supposed to: check if the mobile/cell number is 11 characters long. check if the number starts with 07. If neither of these conditions are met, it should remove the number from the array. So the following numbers would be valid: 07123456789,07123456790,07123456791,07123456792,07123456793,07123456794 However the following wouldn't (and need to be removed): 0801458,07855488,6695522214124514 $param["number"] = "07123456789,07123456790,07123456791,07123456792,07123456793,07123456794,0801458,07855488,6695522214124514"; $number = explode(',', $param["number"]); foreach($number as $num){ if (!substr_compare($num, "07", 0, 3, false)) { unset($num); } elseif (substr_compare($num, "07", 0, 3, true)) { if(strlen($num) == 11) { $li .= "447" . substr($num, 2) . ','; } } } $il .= substr($li, 0, strlen($li)-1); echo $il; // $request = substr($request, 0, strlen($request)-1); // return $n; } I also need to remove the final comma from the result. Any help will be appriciated. Thanks, Kyle

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• How can I make keyword order more relevant in my search?

  - by Atomiton

  In my database, I have a keywords field that stores a comma-delimited list of keywords. For example, a Shrek doll might have the following keywords: ogre, green, plush, hero, boys' toys A "Beanie Baby" doll ( that happens to be an ogre ) might have: beanie baby, kids toys, beanbag toys, soft, infant, ogre (That's a completely contrived example.) What I'd like to do is if the consumer searches for "ogre" I'd like the "Shrek" doll to come up higher in the search results. My content administrator feels that if the keyword is earlier in the list, it should get a higher ranking. ( This makes sense to me and it makes it easy for me to let them control the search result relevance ). Here's a simplified query: SELECT p.ProductID AS ContentID , p.ProductName AS Title , p.ProductCode AS Subtitle , 100 AS Rank , p.ProductKeywords AS Keywords FROM Products AS p WHERE FREETEXT( p.ProductKeywords, @SearchPredicate ) I'm thinking something along the lines of replacing the RANK with: , 200 - INDEXOF(@SearchTerm) AS Rank This "should" rank the keyword results by their relevance I know INDEXOF isn't a SQL command... but it's something LIKE that I would like to accomplish. Am I approaching this the right way? Is it possible to do something like this? Does this make sense?

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• Excel VBA: can delete validation but not add new one

  - by user1882965

  My code is as follows If Cells(Target.Row, 2) = "" And (Cells(Target.Row, 3) = "" Or Cells(Target.Row, 3) = "") Then Sheets("MySheet").Activate Cells(Target.Row, 3).Activate ActiveCell.Validation.Delete If (Cells(Target.Row, 2) = "Type A") Then ActiveCell.Validation.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:=xlBetween, Formula1:="=AvailableVersions" ElseIf (Cells(Target.Row, 2) = "Type B") Then ActiveCell.Validation.Delete Else ActiveCell.Validation.Add Type:=xlValidateWholeNumber, AlertStyle:=xlValidAlertInformation, Formula1:="0", Formula2:="9999999" End If End If So the issue I am having comes whenever I reach ActiveCell.Validation.Add Run Time Error '1004': Application-defined or object-defined error Not a very helpful error, and also this occurs with both number and list validation type, so I am sure it is not an issue with the list itself which has workbook level scope anyway. It never occurs on ActiveCell.Validation.Delete which I find weird? I have been all over google trying to find a solution, and most suggest that it is caused by running dynamic validation code from a button which hogs focus despite the Activate call, but I am running on sheet change event rather than on button press so I don't think this is my issue - any ideas? I've wasted basically a whole day on this! :(

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• most efficient method of turning multiple 1D arrays into columns of a 2D array

  - by Ty W

  As I was writing a for loop earlier today, I thought that there must be a neater way of doing this... so I figured I'd ask. I looked briefly for a duplicate question but didn't see anything obvious. The Problem: Given N arrays of length M, turn them into a M-row by N-column 2D array Example: $id = [1,5,2,8,6] $name = [a,b,c,d,e] $result = [[1,a], [5,b], [2,c], [8,d], [6,e]] My Solution: Pretty straight forward and probably not optimal, but it does work: <?php // $row is returned from a DB query // $row['<var>'] is a comma separated string of values $categories = array(); $ids = explode(",", $row['ids']); $names = explode(",", $row['names']); $titles = explode(",", $row['titles']); for($i = 0; $i < count($ids); $i++) { $categories[] = array("id" => $ids[$i], "name" => $names[$i], "title" => $titles[$i]); } ?> note: I didn't put the name = value bit in the spec, but it'd be awesome if there was some way to keep that as well.

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• doubt in sizeof implementation

  - by aks

  Below is the program to find the size of a structure without using sizeof operator: struct MyStruct { int i; int j; }; int main() { struct MyStruct *p=0; int size = ((char*)(p+1))-((char*)p); printf("\nSIZE : [%d]\nSIZE : [%d]\n", size); return 0; } My doubt is: Why is typecasting to char * required? If I don't use the char* pointer, the output is 1 - WHY?

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• NASM shift operators

  - by Hudson Worden

  How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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• File::GlobMapper doesnt seem to be exporting globmap

  - by justintime

  The following is pretty well copied from the documentation. use File::GlobMapper qw( globmap ); for my $pair (globmap '<*.tar.gz>' => '<#1.tgz>' ) { } And it gives String found where operator expected at globmapper_test1.pl line 4, near "globmap '<*.tar.gz>'" (Do you need to predeclare globmap?) (Using ActivePerl 5.10.0 on Windows) Side questions - if GlobMapper only exports one function, why is it set so you have to export it explicitly?

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• Template type deduction with a non-copyable class

  - by Evan Teran

  Suppose I have an autolocker class which looks something like this: template <T> class autolocker { public: autolocker(T *l) : lock(l) { lock->lock(); } ~autolocker() { lock->unlock(); } private: autolocker(const autolocker&); autolocker& operator=(const autolocker&); private: T *lock; } Obviously the goal is to be able to use this autolocker with anything that has a lock/unlock method without resorting to virtual functions. Currently, it's simple enough to use like this: autolocker<some_lock_t> lock(&my_lock); // my_lock is of type "some_lock_t" but it is illegal to do: autolocker lock(&my_lock); // this would be ideal Is there anyway to get template type deduction to play nice with this (keep in my autolocker is non-copyable). Or is it just easiest to just specify the type?

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• Prolog for beginners about logic and syntax

  - by lnotik

  Hello everybody. I have this question : I need to create a paradict "rightGuesses" which will get 3 arguments , each one of them is a list of letters : 1) The list of guessed letters 2) The word i have to guess 3) The letters that where guessed so far . for example : rightGuesses([n,o,p,q], [p,r,o,l,o,g], Ans). will give us Ans = [p, -, o, -, o, -]. i made: rightGuesses([],T2,[ANS]) rightGuesses([A|T1],T2,[ANS]):- (member(A,T2))=\=true , rightGuesses(T1,T2,[ _ |'-']). rightGuesses([A|T1],T2,[ANS]):- member(A,T2), rightGuesses(T1,T2,[ _ |A]). but i get : ERROR: c:/users/leonid/desktop/file3.pl:5:0: Syntax error: Operator expected Warning: c:/users/leonid/desktop/file3.pl:6: when i trying to compile it what is my problem , and is there is a better way to do it ? thanks in advance.

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• rails - Redirecting console output to a file

  - by egarcia

  On a bash console, if I do this: cd mydir ls -l > mydir.txt The operator captures the standard input and redirects it to a file; so I get the listing of files in mydir.txt instead of in the standard output. Is there any way to do something similar on the rails console? I've got a ruby statement that generates lots of prints (~8k lines) and I'd like to be able to see it completely, but the console only "remembers" the last 1024 lines or so. So I thought about redirecting to a file - If anyone knows a better option, I'm all ears.

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