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  • Matching of tuples

    - by Jack
    From what I understood I can use pattern-matching in a match ... with expression with tuples of values, so something like match b with ("<", val) -> if v < val then true else false | ("<=", val) -> if v <= val then true else false should be correct but it gives me a syntax error as if the parenthesis couldn't be used: File "ocaml.ml", line 41, characters 14-17: Error: Syntax error: ')' expected File "ocaml.ml", line 41, characters 8-9: Error: This '(' might be unmatched referring on first match clause.. Apart from that, can I avoid matching strings and applying comparisons using a sort of eval of the string? Or using directly the comparison operator as the first element of the tuple?

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  • Boost::Container::Vector with Enum Template Argument - Not Legal Base Class

    - by CuppM
    Hi, I'm using Visual Studio 2008 with the Boost v1.42.0 library. If I use an enum as the template argument, I get a compile error when adding a value using push_back(). The compiler error is: 'T': is not a legal base class and the location of the error is move.hpp line 79. #include <boost/interprocess/containers/vector.hpp> class Test { public: enum Types { Unknown = 0, First = 1, Second = 2, Third = 3 }; typedef boost::container::vector<Types> TypesVector; }; int main() { Test::TypesVector o; o.push_back(Test::First); return 0; } If I use a std::vector instead it works. And if I resize the Boost version first and then set the values using the [] operator it also works. Is there some way to make this work using push_back()?

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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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  • 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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  • Sort CMap Key by String Length

    - by Yan Cheng CHEOK
    Previously, I am using STL map to perform the mentioned task. struct ltstr { bool operator()(std::string s1, std::string s2) const { const int l1 = s1.length(); const int l2 = s2.length(); if (l1 == l2) { // In alphabetical order. return s1.compare(s2) < 0; } // From longest length to shortest length. return l1 > l2; } }; std::map<std::string, int, ltstr> m; How can I perform the same task using CMap? // How to make key sorted by string length? CMap<CString, LPCTSTR, int, int> m;

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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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  • 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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  • Permissions in OS X for iTunes library with multiple users

    - by John
    I currently have a lot of music on an external drive and my iTunes set up from there. However, periodically, when the external drive isn't connected, iTunes will default back to the library location of my home directory user path. I don't want to mess with an external drive, as my Mac's HD is large enough to house the music collection. However, I have 4 family members – all with their own logins – using this same gob of music. I don't want four copies of the library, only one with all libraries referencing it. So, what I want to do is: Move all music files to a shared directory at /Macintosh HD/users/music. I created this directory and adjusted permissions, so all four users can read and write to this directory. Get all four accounts to reference this library instead of the external or local home locations I am hoping I can just check the box to keep library organized in my account, which is the admin and let iTunes move it all. Then delete current libraries for each account and re-add from the new shared location. Will the iTunes organization process cause permissions issues either by setting permissions to all the files access to my account only or write permissions or any other 'gotcha'? I am having a hard time coming up with a smooth solution that won't break everything and cause me to have mega duplicates or access issues. I would prefer not to do any XML library file editing if possible. Am I dreaming?

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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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  • 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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  • 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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  • Accessing clearcase view drive from virtual machine is slow

    - by PermanentGuest
    I have a windows XP virtual machine running under a Windows XP host. On the host : On the host clearcase 7.1.1.2 is installed. I have a dynamic view mapped onto some drive. The view has certain VOB/directory structure where my application DLLs from the nightly build and config files are stored. I run my application on the host machine which uses the DLLs and config files from the VOB and everything runs smooth. Now I want to move this set-up to a virtual machine. On the guest : I'm running the guest with a vm-player. I don't want to install clear-case on this as I don't want to expose this machine onto the network. The network setting in the guest is 'host-only'. I have mapped the host's clearcase view drive as a shared folder and I'm able to access this drive from the virtual machine. Also, the application is running. However, the problem is that the access of the clearcase drive from the virtual machine is very slow. I can experience this from the windows explorer. Due to this, the starting of my application takes several seconds in the virtual machine while on the guest it comes up pretty fast. My question is : Is there any way to speed up the performance? I have managed to copy some of the DLLs which don't change frequently to the virtual machine to improve the performance. However, there are still lot of DLLs which have to be taken from the clearcase drive as they change frequently. VMplayer version is : VM Player 3.0.1 build-227600 Both guest and host is : Windows XP service pack 3 Host clearcase is : clearcase 7.1.1.2

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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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  • 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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  • Outlook 2007 + Exchange 2010 (Save All Attachments)

    - by RobertPitt
    About 3 weeks back our company upgraded our mail system to Exchange 2010, all went smooth, few issues but nothing major. A few days ago we had a call from a colleague where he was unable to save all attachments, From File > Save As > Save All Attachments. When the email has a single attachment it works perfectly normal, and depending on the file type it allows you to save multiple attachments. But there's a lot of file types that will not work, such as zip, pdf, doc etc, Usually we get a location box open up asking where we would like to drop the attachments, but it does nothing, You click Save All Attachments and nothing happens. After hours of research I have come across mixed results, a lot of people on forums have been explaining that they have recently crossed over to Exchange 2010 and there issues started there. But on the other hand Microsoft released a KB (278188) which was depressing if that, but that article was published in 2007, as stated by the time stamp, and Exchange 2010 has only come out recently. Im looking to see if you guys have any clues what could be causing this, anything server side that I can take a look at (AD, Exchange, ...). Any help on this is greatly supported

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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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  • 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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  • 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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  • 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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  • 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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  • HP EliteBook 8440P - USB ports stop working on docking station

    - by r0ca
    I have a HP Elitebook 8440P running Windows XP Pro SP3. I installed it on my docking station and everything went smooth for a while. Last week, my mouse and any other USB devices stoped working sudenly... It was working fine on my laptop itself but nothing on my docking station. LCD attached monitor works and same for LAN and PS2 keyboard. I updated the BIOS, Chipset, Video Drivers, also changed my docking station by a brand new one but the problem still comes back. I also noticed something in Device Manager... A Generic USB Root Hub has an error on it, a Yellow/Orange exclamation mark. I tried to update that driver but no luck. Windows is unable to process it. This seems to be the problem but can't fix it. I may only re-image my laptop but for me, I need to avoid that since I have so many apps installed on it. If anybody has any advice, I'll take it!

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  • Alfa AWUSO36H 1W dysfunctional driver

    - by BrainStorm
    I recently purchased an Alfa AWUSO36H 1W wireless USB adapter for my notebook, in order to improve signal strength and quality. I'm currently using Linux Mint 11, and the it uses the RTL8187 driver for this adapter, I'm also using a 4dbi antenna, though I have others. The problem is that this adapter does exactly the opposite of what it should, actually my internal Broadcom BCM4313 adapter works way better than the alfa. Browsing is slow, some network applications don't even work, pings against Google.com on the internal adapter runs smooth, while in the alfa it gets like 25% packets lost or more! I'm less them 50 feet from my AP, the internal adapter gets 44/70 link quality, and the alfa gets around 60/70 (iwconfig output). Also the system always sets alfa power to 20dbm(100mw), then I have to do sudo iw set reg B0 to make it 30dbm(1000mw), but apparently no significant change. I've installed wireless-compat drivers, no change either. And worst of all, in Windows 7 it works way more smoothly for browsing, though I couldn't test it properly there. I hope its a driver problem, even if it's a pain to find/compile Linux drivers for a starter, I prefer it to a hardware problem where I would need to buy another adapter, since I have no money left (except for the cantenna pieces).

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  • What are the differences between these three patterns of "class" definitions in JavaScript?

    - by user1889765
    Are there any important/subtle/significant differences under the hood when choosing to use one of these three patterns over the others? And, are there any differences between the three when "instantiated" via Object.create() vs the new operator? The pattern that CoffeeScript uses when translating "class" definitions: Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.move = function(meters) { return alert(this.name + (" moved " + meters + "m.")); }; return Animal; })(); and The pattern that Knockout seems to promote: var DifferentAnimal = function(name){ var self = this; self.name = name; self.move = function(meters){ return alert(this.name + (" moved " + meters + "m.")); }; return {name:self.name, move:self.move}; } and The pattern that Backbone promotes: var OneMoreAnimal= ClassThatAlreadyExists.extend({ name:'', move:function(){} });

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